Carotenoid production methods using raceway pond systems

Abstract

A method for producing a carotenoid, wherein the method comprises a first algal culture phase comprising culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds a

Description

All documents cited herein are incorporated by reference in their entirety. TECHNICAL FIELD The present invention relates to methods for producing carotenoids by culturing algae in land-based mariculture. BACKGROUND Natural p-carotene is commercially isolated from many different sources including hypersaline microalgae, fungus, and fruit. Commercial p-carotene production includes isolation from Dunaliella salina (hypersaline chiorophyte microalga), Blakeslea trispora (fungus), Daucus carota (root vegetable) and a large selection of fruit such as Elaeis guineensis (oil palm), Citrus sinensis (oranges) or Mangifera indica (mango) among many other fruit and vegetables. p-carotene is also produced by chemical synthesis since the 1950s through the combination of two 15-carbon phosphonium salts being added on each side of a 10-carbon dialdehyde in the Wittig reaction, with subsequent isomerization to create a symmetric compound (Ernst, Henrich and Keller, 2003). Alternatively, it is produced via the Grignard reaction to combine a long-chain diketone with two methanol molecules. However, large quantities (at very large doses with an LD50 >5,000 mg / kg) of pure chemically synthesized p-carotene (often used as a pure colorant) have been implicated in exacerbation of UV-carcinogenesis for example (Black et aL, 2020). For this reason, biological p-carotene extracts orthose in combination with natural a-tocopherols are preferred for human dietary supplementation, as these show significantly less carcinogenic exacerbation. Natural p-carotene extracts often contain a large number of isomers created during biosynthesis, metabolic modification or as the result of the extraction conditions. These include amongst others a\\-trans, 9-cis, 13-c / s, 15-c / s, 5,13-c / s, 8,9-c / s (^-carotene) as well as similar carotenoids such as a-carotene, lycopene, and lutein. Depending on the method of extraction these natural extracts may also contain traces of chlorophyll and its derivatives. Due to the higher degree of intestinal absorption of all-frans p-carotene relative to other isomers such as 9-cis p-carotene for example, generally all-trans sources of p-carotene are preferred for human nutritional supplementation (Johnson et al., 1997). In humans, p-carotene is the primary precursor of vitamin A and therefore often referred to as provitamin-A and is implicated in retinal photoreception but also proper functioning of brain health, the immune system, treatment of erythropoietic protoporphyria (sun sensitivity), and in the prevention of metabolic syndrome related diseases. Because of its biomedical value p-carotene is a high value product for human consumption and there is a well-documented commercial market for natural p-carotene extracts (Grune et al, 2010). In Europe p-carotene has been evaluated as a food additive by the Joint FAO / WHO Expert Committee on Food Additives (JEFCA) in 2001 and by the Scientific Committee on Food (SCF) in 1997 and 2000, assigned an E-number (E160a (ii) - for p-carotene extracts) and re-evaluated the assignment of Acceptable Daily Intake (ADI) in the Commission Directive 2008 / 128 / EC (for regular consumption <10 mg / day). In the United States the FDA has recognized it as a ‘generally recognized as safe’ (GRAS) substance for food additives. Because of the lipophilic nature of p-carotene, there are multiple commercial extraction methods from biomass including super-critical and sub-critical carbon-dioxide extraction, solvent extraction and oil extraction (Mendes et al, 1995). ‘Milking’ of live microalgae by passing these through food grade oils, where the p-carotene transfers from the algae to the oil without disrupting the cells, has been evaluated. These extraction methods are often accompanied by pre-treatment methods to mechanically break or disrupt complex plant cell walls such as ultra-sonication, high-pressure homogenization (HPH), shear or grinding. Electro-technology-assisted extraction methods, such as pulsed electric field (PEF), moderate electric field (MEF), high-voltage electric discharges (HVED) or pressurized liquid extraction (PLE), and microwave-assisted extraction (MAE) have also been used. To increase the extraction efficiency, wet or dry biomass is sometimes emulsified in a solvent or solvent mixes often with the addition of process aides such as proteases or emulsification agents (Correa et al, 2020; Gupta et al, 2021). Many organic solvents such acetone, hexane, chloroform or dichloromethane have been used to extract carotenoids from biomass. Food grade organic solvents such as acetic-esters of C1-C4 alcohols, hot ethanol as well as ‘green’ solvents like limonene have been used. Similarly, food oils such as olive, canola or other vegetable oils are used for extraction (Ghazi, 1999). After extraction into an organic phase, many additional purification steps are used to remove carbohydrates, lipids, proteins, water, other carotenoids and pigments. These purification steps often include the preparation of oleoresins, hydrolysis of biological molecules and alkaline saponification. Multiple physical concentration methods through semi-permeable membranes, precipitation and evaporation are common (Correa et al, 2020). There is a need for more efficient methods for producing high quality natural carotenoid extracts. SUMMARY OF THE INVENTION The invention relates to a production system based on culturing algae in raceway ponds to create a very high-throughput, highly scalable and highly sustainable carotenoid production system. The inventors’ methods involve a ‘hurry up and wait’ approach to algal cultivation, in which growth rates are maximised upstream for maximum throughput, and decreased quickly via intensive stressing before harvest. In some instances, a ‘split pond’ approach is deployed, in which the pond train becomes non-linear to facilitate the ‘hurry up and wait’ approach, with a maximal increase in light stress pre-harvest. The high-throughput algal culture system comprises two principal phases. In the first phase, algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition. The algae typically contain low levels of carotenoids during this phase. In the second phase, the cultivation conditions are adjusted to deliberately induce the formation of carotenoids, typically by stressing the cells through one or more of nutrient limitation, high salinity, low temperature and / or increasing light exposure. The ‘in-sequence’ switch from maximizing growth to maximizing carotenoid content at the end of a connected series of raceway ponds results in highly efficient carotenoid production. Carotenoid extraction directly from fresh, wet biomass (such as an algal slurry) contributes to the overall objective of producing carotenoids in an environmentally friendly and cost-effective way. In particular, carotenoid extraction from wet biomass avoids the need for an energy-intensive drying step which would result in detrimental effects on the environment and increased production costs. The present application shows that carotenoid extraction from algae is possible without such a drying step. Furthermore, carotenoid extraction from wet biomass is more efficient than extraction from dry biomass. In some instances, the inventors’ methods combine: (1) high-throughput algal culture, (2) high-throughput harvesting to result in a live slurry of concentrated algal cells, (3) carotenoid extraction from fresh wet biomass and (4) purification and separation of carotenoids with minimal processing steps. The inventors have provided guidance on methods for culturing algae in United Kingdom Patent Application Nos. 2207837.2, 2303156.0, 2212805.2, 2308480.9, 2212809.4 and 2308479.1, as well as International Patent Application Nos. PCT / GB2023 / 051392, PCT / GB2023 / 052278 and PCT / GB2023 / 052279. The inventors have also provided guidance on culturing algae with remote optical monitoring in United Kingdom Patent Application No. 2303165.1. The inventors have also provided guidance on carotenoid production methods in United Kingdom Patent Application No. 2301206.5 and International Patent Application No. PCT / GB2024 / 050230. Each of these patent applications is incorporated herein by reference. The invention provides a method for producing a carotenoid, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition, (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen), thereby inducing the algae to increase carotenoid production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b), and (d) an extraction phase, wherein the extraction phase comprises extracting the carotenoid from the algae harvested in step (c). In some embodiments, the carotenoid is beta-carotene. In some embodiments, upon transfer into each of the one or more induction raceway ponds, the algae are cultured in water that is at least 10% shallower than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the algae are cultured in shallower water, for at least the first day following transfer into each of the one or more induction raceway ponds, than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the mean photosynthetically active radiation (PAR) and UV light does not exceed the light photoinhibition parameter (Ekp) of the algae. In some embodiments, the culture water depth is at least 20 cm in the induction raceway pond(s). In some embodiments, the one or more induction raceway ponds in step (b) comprise at least two induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds. In some embodiments, the one or more induction raceway ponds in step (b) comprise at least two series of induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds. In some embodiments, each of the at least two series of induction raceway ponds comprises at least two induction raceway ponds that are connected, in parallel, to the first induction pond in the series. In some embodiments, each of the at least two series of induction raceway ponds comprises at least three induction raceway ponds that are connected, in parallel, to the first induction pond in the series. In some embodiments, in each of the series of induction raceway ponds, the algae are cultured in (10%) shallower water upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, the harvesting algae in step (c) is from the final induction ponds. In some embodiments, the algae are green during the first algal culture phase, and wherein the algae become beige or orange during the second algal culture phase. In some embodiments, the marine carotenoid-producing microalgae are Chlorophyta, Chlorarachniophyta, Haptophyta, Dinophyta, Euglenophyta, Heterokontophyta (e.g. Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, Xanthophyceae or Eustigmatophyceae), Cryptophyta, unicellular Rhodophyta, Glaucophyta or Cyanophyta, optionally wherein the marine carotenoid-producing microalgae are: (i) Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema sp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., or (ii) Dunaliella sp. In some embodiments, the carotenoid is beta-carotene. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta, Chlorarachniophyta, Haptophyta, Dinophyta, Euglenophyta, Heterokontophyta (e.g. Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, Xanthophyceae or Eustigmatophyceae), unicellular Rhodophyta, Glaucophyta or Cyanophyta, optionally wherein the marine carotenoid-producing microalgae are: Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema sp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., or (ii) Dunaliella sp. In some such embodiments, the marine carotenoid-producing microalgae are Dunaliella sp. (e.g. D. salina). In some embodiments, the carotenoid is a xanthophyll. In some embodiments, the xanthophyll is lutein. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta (e.g. Dunaliella sp.) or Chlorarachniophyta. In some such embodiments, the marine carotenoid-producing microalgae are Dunaliella sp. (e.g. D. salina). In some embodiments, the xanthophyll is: (A) diadinoxanthin, optionally wherein the marine carotenoid-producing microalgae are Heterokontophyta (e.g. Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, orXanthophyceae), Haptophyta, Dinophyta or Euglenophyta, (B) zeaxanthin, optionally wherein the marine carotenoid-producing microalgae are Chlorophyta, Chlorarachniophyta, Haptophyta, Dinophyta, Euglenophyta, Heterokontophyta (e.g., Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, orXanthophyceae), Cryptophyta, unicellular Rhodophyta, Glaucophyta or Cyanophyta, optionally further wherein the marine carotenoid-producing microalgae are: (i) Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema spp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp., or Nitzschia sp., or (ii) Dunaliella sp., or (iii) Trichodesmium sp., Richelia sp., Calothrix sp., Crocosphaera sp., or Candidatus Atelocyanobacterium Thalassa, (C) violaxanthin, optionally wherein the marine carotenoid-producing microalgae are Chlorophyta (e.g. Dunaliella sp.), Chlorarachniophyta, or Heterokontophyta (e.g. Raphidophyceae, Phaeophyceae, or Eustigmatophyceae), (D) neoxanthin, optionally wherein the marine carotenoid-producing microalgae are Euglenophyta, Chlorophyta (e.g. Dunaliella sp.) or Chlorarachniophyta, (E) fucoxanthin, optionally wherein the marine carotenoid-producing microalgae are Heterokontophyta (e.g. Chrysophyceae, Raphidophyceae, Bacillariophyceae, or Phaeophyceae), Haptophyta, or Dinophyta, optionally further wherein the marine carotenoid-producing microalgae are Rhopalodiaceae sp. Hemiaulus sp., Climacodium sp., Skeletonema spp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., (F) vaucheriaxanthin, optionally wherein the marine carotenoid-producing microalgae are Heterokontophyta (e.g. Chrysophyceae or Eustigmatophyceae), (G) loroxanthin, optionally wherein the marine carotenoid-producing microalgae are Euglenophyta, Chlorophyta (e.g. Prasinophyceae, Chlorophyceae or Ulvophyceae) or Chlorarachniophyta, (H) siphonaxanthin, optionally wherein the marine carotenoid-producing microalgae are Euglenophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae or Ulvophyceae), (I) one or more of nostoxanthin, echinenone, myxol glycosides and oscillol glycosides, optionally wherein the marine carotenoid-producing microalgae are Cyanophyta, optionally further wherein the marine carotenoid-producing microalgae are Trichodesmium sp., Richelia sp., Calothrix sp., Crocosphaera sp. or Candidatus Atelocyanobacterium Thalassa, (J) one or more of alloxanthin, crocoxanthin and monadoxanthin, optionally wherein the marine carotenoid-producing microalgae are Cryptophyta, (K) violaxanthin fatty acid ester, optionally wherein the marine carotenoid-producing microalgae are Heterokontophyta (e.g., Xanthophyceae), (L) fucoxanthin fatty acid ester, optionally wherein the marine carotenoid-producing microalgae are Haptophyta, (M) peridinin, optionally wherein the marine carotenoid-producing microalgae are Dinophyta, (N) prasinoxanthin, optionally wherein the marine carotenoid-producing microalgae are Chlorophyta (e.g., Prasinophyceae), (0) loroxanthin fatty acid ester, optionally wherein the marine carotenoid-producing microalgae are Chlorophyta (e.g,. Prasinophyceae) or Chlorarachniophyta, or (P) siphonaxanthin fatty acid ester, optionally wherein the marine carotenoid-producing microalgae are Chlorophyta (e.g. Prasinophyceae, Chlorophyceae or Ulvophyceae). In some embodiments, the algal culture is diluted in each raceway pond in the first algal culture phase, and wherein pond volume for each pond in the first algal culture phase is modelled by the following equation: Vj = Vo ■ wherein V1 is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. In some embodiments, the algal culture is diluted in each induction raceway pond in the second algal culture phase, and wherein pond volume for each pond in the second algal culture phase is modelled by the following equation: Vi = Vo • wherein Vi is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. In some embodiments, the algal growth rate during step (a) is at least 0.7d 1 (e.g. 0.7-1.0 d 1) and / or wherein the algal growth rate at the end of step (b) is less than 0.6 d-1 (e.g. 0.5 d-1). In some embodiments, the series of connected raceway ponds in step (a) is a linear series. In some embodiments, the series of connected raceway ponds in step (a) comprises a first stage comprising one or more covered raceway ponds and a second stage comprising one or more stages of open raceway ponds. In some embodiments, one or more nutrient mineral acids are added during step (a), optionally wherein the one or more nutrient mineral acids are selected from nitric acid, phosphoric acid and silicic acid. In some embodiments, the concentration of nitrogen in step (b) is less than 10 pM. In some embodiments, the second algal culture phase is performed for at least four days (e.g. 4-10 days). The invention further provides a method for producing a carotenoid, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition, (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) at a low temperature (e.g. less than 20°C), thereby inducing the algae to increase carotenoid production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b), and (d) an extraction phase, wherein the extraction phase comprises extracting the carotenoid from the algae harvested in step (c). The invention provides a method for producing a carotenoid, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition, (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of high salinity (e.g. at least 40 parts per thousand (%o)), thereby inducing the algae to increase carotenoid production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b), and (d) an extraction phase, wherein the extraction phase comprises extracting the carotenoid from the algae harvested in step (c). BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates an example raceway pond according to the invention. Figure 2A illustrates an algal cultivation system and depicts a series of connected raceway ponds arranged in stages. Figure 2B illustrates a subsection of the algal cultivation system of Figure 2A. Figure 3 illustrates exemplary extraction methods according to the invention. Figure 4A is a chromatogram for crude carotenoid extract. Figure 4B is a chromatogram for carotenoid powder 84% all-trans beta carotene. Figure 4C is a chromatogram for BASF Betatene® 30% OLV, 72% all-trans beta carotene. Figure 5A is a chromatogram for lutein extract (45 min run time). Figure 5B is a chromatogram for lutein extract (60 min run time). Figure 6 is a chromatogram for crude extract obtained from Skeletonema pseudocostatum. Figure 7 provides structural formulae for some exemplary carotenoids. This figure is reproduced from Takaichi 2011. Figure 8 provides a summary of carotenoid distribution in algae. This figure is reproduced from Takaichi 2011. (Key: H, Major carotenoid in most species of the class; L, Low content in most species or major carotenoid in some species, a, a-carotene; p, p-carotene; Al, alloxanthin; Cr, crocoxanthin; Da, diatoxanthin; Dd, diadinoxanthin; Ec, echinenone; FA, fatty acid ester; Fx, fucoxanthin; Lo, loroxanthin; Lu, lutein; Mo, monadoxanthin; My, myxol glycosides and oscillol glycosides; Ne, neoxanthin; No, nostoxanthin; Pe, peridinin; Pr, prasinoxanthin; Sx, siphonaxanthin; Va, vaucheriaxanthin; Vi, violaxanthin; Ze, zeaxanthin). Lu, Lo, Lo-FA, Cr, Mo, Pr, Sxand Sx-FA are a-carotene derivatives. Figure 9 provides an overhead view of a production pond containing a central divider, paddlewheel and deflectors, where a) is the channel length, b) is the pond length, c) is the channel width and d) is the pond width. Multiplying a) by d) gives the centre pond area. The pond aspect ratio is calculated by dividing a) by c). This ratio can be adjusted without effecting the pond gas exchange rates as pond surface area is constant. A ratio of 8 is advantageous in that it facilitates construction from the geomembrane roll and optimises for centre channel mixing velocities. Figure 10 shows modelled in-pond Spectral Photosynthetic Active Radiation (SPAR) at the surface (0m), half fill depth (0.5m) and full pond depth (1m) for Dunaliella salina. The differences in SPAR at depth is due to differences in species-specific absorption and / or scattering properties. The sum of all SPAR values at a specific depth within the visible range (A400-700) equals the PAR (pmol photons m 2 s1) at that same depth. DETAILED DESCRIPTION OF THE INVENTION Carotenes Carotenes are one of the two major divisions of carotenoids. The other division is formed by the xanthophylls. While carotenes are purely hydrocarbons, xanthophylls contain oxygen atoms, typically as a hydroxyl group. Carotenes are terpenoids assembled from eight isoprene units resulting in 40 branched and double bonded carbon atoms, capped with beta-ionone rings at each end. Beta-carotene is a member of the carotene family of compounds. In nature, beta-carotene is biosynthesized from geranylgeranyl pyrophosphate. Like most of the naturally occurring carotenoids, it is strongly colored and highly lipophilic (since it lacks functional groups). The invention provides a method for producing a carotene, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition, (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), and wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen), thereby inducing the algae to increase production of carotene; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b), and (d) an extraction phase, wherein the extraction phase comprises extracting carotene from the algae harvested in step (c). In some embodiments, upon transfer into each of the one or more induction raceway ponds, the algae are cultured in water that is at least 10%, at least 15%, at least 20%, or at least 25% shallower than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, upon transfer into each of the one or more induction raceway ponds, the algae are cultured in water that is 10-25% shallower than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the algae are cultured in shallower water, for at least the first day following transfer into each of the one or more induction raceway ponds, than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the algae are cultured in shallower water, for the first day following transfer into each of the one or more induction raceway ponds, than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the mean photosynthetically active radiation (PAR) and UV light does not exceed the light photoinhibition parameter (Ekp) of the algae. In some embodiments, the culture water depth is at least 20 cm in the induction raceway pond(s). Advantageously, this enhances paddlewheel mixing and reduces the likelihood of overexposure to UV. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise at least two induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise at least two series of induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds. In some embodiments, each of the at least two series of induction raceway ponds comprises at least two induction raceway ponds that are connected, in parallel, to the first induction pond in the series. In some embodiments, each of the at least two series of induction raceway ponds comprises at least three induction raceway ponds that are connected, in parallel, to the first induction pond in the series. In some embodiments, in each of the series of induction raceway ponds, the algae are cultured in (10%) shallower water upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, algae are harvested from the final induction pond(s). In some embodiments, the algae are green during the first algal culture phase. In some embodiments, the algae become beige or orange during the second algal culture phase. In preferred embodiments, the carotene is beta-carotene. In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Heterokontophyta, Haptophyta, Dinophyta, Euglenophyta, Chlorarachniophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae). In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Heterokontophyta, Haptophyta, Euglenophyta, Chlorarachniophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae). In some such embodiments, the marine carotenoid-producing microalgae are: (i) Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema sp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., or (ii) Dunaliella sp.. In some such embodiments, the marine carotenoid-producing microalgae are Dunaliella sp., such as Dunaliella salina. In some embodiments, the algal culture is diluted in each raceway pond in the first algal culture phase, and wherein pond volume for each pond in the first algal culture phase is modelled by the following equation: Vj = Vo ■ 2(15¾)) wherein V1 is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. In some embodiments, the algal culture is diluted in each induction raceway pond in the second algal culture phase, and wherein pond volume for each pond in the second algal culture phase is modelled by the following equation: m V| — Vg ■ wherein V1 is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. In some embodiments, the algal growth rate during step (a) is at least 0.7d-1 (e.g. 0.7-1.0 d-1) and / or wherein the algal growth rate at the end of step (b) is less than 0.6 d-1 (e.g. 0.5 d-1). In some embodiments, the series of connected raceway ponds in the first algal culture phase is a linear series. In some embodiments, the series of connected raceway ponds in the first algal culture phase comprises a first stage comprising one or more covered raceway ponds and a second stage comprising one or more stages of open raceway ponds. In some embodiments, one or more nutrient mineral acids are added during the first algal culture phase, optionally wherein the one or more nutrient mineral acids are selected from nitric acid, phosphoric acid and silicic acid. In some embodiments, the concentration of nitrogen in step (b) is less than 10 pM. In some embodiments, the second algal culture phase is performed for at least four days (e.g.4-10 days). In some embodiments, the carotene is alpha-carotene. In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Cryptophyta, Prasinophyceae, Chlorophyceae or Ulvophyceae. In some such embodiments, the marine carotenoid-producing microalgae are Cryptophyta or Chlorophyceae. In some embodiments, wherein said extracting in step (d) comprises: (i) suspending the algal slurry in an alkyl-ester solvent, (ii) separating the alkyl-ester solvent phase from the water phase, (iii) evaporating the alkyl-ester solvent to generate an oleoresin, wherein water is added before or during evaporation, (iv) saponifying the oleoresin to generate a slurry that comprises the carotene, and (v) filtering the slurry to generate a filter cake that comprises the carotene. In some embodiments, the alkyl-ester solvent in step d(i) is ethyl acetate. In some embodiments, the alkyl-ester solvent in step d(i) is food-grade ethyl acetate. In some embodiments, the alkyl-ester solvent in step d(i) is 100% food-grade ethyl acetate. In some embodiments, step (d)(i) further comprises agitating the suspended slurry. This is advantageous when the microalgae are difficult to break open, such as when Dunaliella salina has formed storage cysts. In contrast, many diatoms have silicate frustules (cell walls) that are similar to a fine mesh, and so do not require agitation to extract carotenoids. In some embodiments, the algal slurry comprises at least 10% dry weight, wet biomass. In some such embodiments, suspension of the algal slurry in the alkyl-ester solvent (e.g., (100% food-grade) ethyl acetate) provides a 10-100 g / L (e.g., 40-60 g / L) dry weight suspension. In some embodiments, step (d)(ii) further comprises depth filtration of the alkyl-ester solvent phase. Advantageously, this facilitates the removal of particulate biomass. In some embodiments, the water is added to the alkyl-ester solvent in a volume ratio of 0.2-5 to 1, such as 1:1. Advantageously, this reduces the quantity of oleoresin that adheres to vessel walls to facilitate further processing and to avoid a second resuspension process. In some embodiments, step (d)(iii) is performed by vacuum evaporation. Advantageously, this facilitates performance of the method at lower temperatures, thereby preventing isomerisation of the beta-carotene (into cis-17 and cis-19). In some embodiments, the alkyl-ester solvent is condensed, recaptured and recycled. In some such embodiments, the solvent is passed through a drying column (e.g., a solid phase that selectively absorbs hydrophilic material). This is to ensure that it is dry and clean before reuse. In some such embodiments, the condensed solvent is passed through one or more activated carbon columns. This acts, for example, to remove organic impurities, flavours and off-colour products. In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as a concentrated alkali metal hydroxide solution (e.g. concentrated NaOH or KOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as NaOH (50 wt%), optionally to a final concentration of 0.5-5 M NaOH (e.g., 1-2.5 M NaOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as KOH (50 wt%), optionally to a final concentration of 0.5-5 M KOH (e.g., 1-2.5 M KOH). In some embodiments, step d(iv) is performed at 40-80°C (e.g., 55-65°C). In some such embodiments, step d(iv) is performed for at least 30 minutes (e.g., 60 minutes). In some such embodiments, step d(iv) is performed for 30-90 minutes (e.g., 45-75 minutes). In preferred embodiments, the extraction phase is performed under an inert gas (e.g., a nitrogen blanket). This prevents oxidation of the extracts. High light in combination with high salinity The invention further provides methods that involve deliberately inducing the formation of carotenoids by stressing the cells through increasing light exposure and high salinity. The statements above regarding step (d) are applicable to these methods too. Similarly, the statements regarding steps (a), (b), (c) and (d) provided elsewhere herein are also applicable to these methods. Such methods include a method for producing a carotenoid, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition, (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of the presence of high salinity (e.g. at least 40 parts per thousand (%o)), thereby inducing the algae to increase carotenoid production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b), and (d) an extraction phase, wherein the extraction phase comprises extracting the carotenoid from the algae harvested in step (c). In some embodiments, the algae are induced to produce carotene by culturing the algae with high salinity. In some embodiments, the algae are cultured at a salinity of at least 40 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 50 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 60 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 70 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 80 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 90 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 100 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 110 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 120 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 130 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 140 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 150 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 160 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 170 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 180 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 190 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 200 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of 40-200 parts per thousand (%o). In some embodiments, upon transfer into each of the one or more induction raceway ponds, the algae are cultured in water that is at least 10%, at least 15%, at least 20%, or at least 25% shallower than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, upon transfer into each of the one or more induction raceway ponds, the algae are cultured in water that is 10-25% shallower than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the algae are cultured in shallower water, for at least the first day following transfer into each of the one or more induction raceway ponds, than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the algae are cultured in shallower water, for the first day following transfer into each of the one or more induction raceway ponds, than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the mean photosynthetically active radiation (PAR) and UV light does not exceed the light photoinhibition parameter (Ekp) of the algae. In some embodiments, the culture water depth is at least 20 cm in the induction raceway pond(s). Advantageously, this enhances paddlewheel mixing and reduces the likelihood of overexposure to UV. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise at least two induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise at least two series of induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds. In some embodiments, each of the at least two series of induction raceway ponds comprises at least two induction raceway ponds that are connected, in parallel, to the first induction pond in the series. In some embodiments, each of the at least two series of induction raceway ponds comprises at least three induction raceway ponds that are connected, in parallel, to the first induction pond in the series. In some embodiments, in each of the series of induction raceway ponds, the algae are cultured in (10%) shallower water upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, algae are harvested from the final induction pond(s). In some embodiments, the algae are green during the first algal culture phase. In some embodiments, the algae become beige or orange during the second algal culture phase. In preferred embodiments, the carotene is beta-carotene. In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Heterokontophyta, Haptophyta, Dinophyta, Euglenophyta, Chlorarachniophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae). In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Heterokontophyta, Haptophyta, Euglenophyta, Chlorarachniophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae). In some such embodiments, the marine carotenoid-producing microalgae are: (i) Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema sp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., or (ii) Dunaliella sp.. In some such embodiments, the marine carotenoid-producing microalgae are Dunaliella sp., such as Dunaliella salina. In some embodiments, the algal culture is diluted in each raceway pond in the first algal culture phase, and wherein pond volume for each pond in the first algal culture phase is modelled by the following equation: Vi = Vo • wherein Vi is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. In some embodiments, the algal culture is diluted in each induction raceway pond in the second algal culture phase, and wherein pond volume for each pond in the second algal culture phase is modelled by the following equation: Vt = Vo ’ 2^2^ wherein Vi is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. In some embodiments, the algal growth rate during step (a) is at least 0.7d‘1 (e.g. 0.7-1.0 d-1) and / or wherein the algal growth rate at the end of step (b) is less than 0.6 d-1 (e.g. 0.5 d-1). In some embodiments, the series of connected raceway ponds in the first algal culture phase is a linear series. In some embodiments, the series of connected raceway ponds in the first algal culture phase comprises a first stage comprising one or more covered raceway ponds and a second stage comprising one or more stages of open raceway ponds. In some embodiments, one or more nutrient mineral acids are added during the first algal culture phase, optionally wherein the one or more nutrient mineral acids are selected from nitric acid, phosphoric acid and silicic acid. In some embodiments, the second algal culture phase is performed for at least four days (e.g. 4-10 days). In some embodiments, the carotene is alpha-carotene. In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Cryptophyta, Prasinophyceae, Chlorophyceae or Ulvophyceae. In some such embodiments, the marine carotenoid-producing microalgae are Cryptophyta or Chlorophyceae. High light in combination with low temperature The invention further provides methods that involve deliberately inducing the formation of carotenoids by stressing the cells through increasing light exposure and low temperature. The statements above regarding step (d) are applicable to these methods too. Similarly, the statements regarding steps (a), (b), (c) and (d) provided elsewhere herein are also applicable to these methods. Such methods also include a method for producing a carotenoid, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition, (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) at a low temperature (e.g. less than 20°C), thereby inducing the algae to increase carotenoid production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b), and (d) an extraction phase, wherein the extraction phase comprises extracting the carotenoid from the algae harvested in step (c). In some embodiments, the algae are induced to produce carotene by culturing the algae at low temperature. In some embodiments, the algae are cultured at a temperature of less than 20 °C. In some embodiments, the algae are cultured at a temperature of less than 18 °C. In some embodiments, the algae are cultured at a temperature of less than 15 °C. In some embodiments, the algae are cultured at a temperature of less than 12 °C. In some embodiments, the algae are cultured at a temperature of less than 10 °C. In some embodiments, the algae are cultured at a temperature of between 12 °C and 20 °C. In some embodiments, the algae are cultured at a temperature of between 12 °C and 18 °C. In some embodiments, upon transfer into each of the one or more induction raceway ponds, the algae are cultured in water that is at least 10%, at least 15%, at least 20%, or at least 25% shallower than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, upon transfer into each of the one or more induction raceway ponds, the algae are cultured in water that is 10-25% shallower than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the algae are cultured in shallower water, for at least the first day following transfer into each of the one or more induction raceway ponds, than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the algae are cultured in shallower water, for the first day following transfer into each of the one or more induction raceway ponds, than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds. In some embodiments, the mean photosynthetically active radiation (PAR) and UV light does not exceed the light photoinhibition parameter (Ekp) of the algae. In some embodiments, the culture water depth is at least 20 cm in the induction raceway pond(s). Advantageously, this enhances paddlewheel mixing and reduces the likelihood of overexposure to UV. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise at least two induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise at least two series of induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds. In some embodiments, each of the at least two series of induction raceway ponds comprises at least two induction raceway ponds that are connected, in parallel, to the first induction pond in the series. In some embodiments, each of the at least two series of induction raceway ponds comprises at least three induction raceway ponds that are connected, in parallel, to the first induction pond in the series. In some embodiments, in each of the series of induction raceway ponds, the algae are cultured in (10%) shallower water upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, algae are harvested from the final induction pond(s). In some embodiments, the algae are green during the first algal culture phase. In some embodiments, the algae become beige or orange during the second algal culture phase. In preferred embodiments, the carotene is beta-carotene. In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Heterokontophyta, Haptophyta, Dinophyta, Euglenophyta, Chlorarachniophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae). In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Heterokontophyta, Haptophyta, Euglenophyta, Chlorarachniophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae). In some such embodiments, the marine carotenoid-producing microalgae are: (i) Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema sp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., or (ii) Dunaliella sp.. In some such embodiments, the marine carotenoid-producing microalgae are Dunaliella sp., such as Dunaliella salina. In some embodiments, the algal culture is diluted in each raceway pond in the first algal culture phase, and wherein pond volume for each pond in the first algal culture phase is modelled by the following equation: Vj = Vo ■ 2^^ wherein Vi is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. In some embodiments, the algal culture is diluted in each induction raceway pond in the second algal culture phase, and wherein pond volume for each pond in the second algal culture phase is modelled by the following equation: Vi = Vo ■ 2^^ wherein Vi is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. In some embodiments, the algal growth rate during step (a) is at least 0.7d-1 (e.g. 0.7-1.0 d-1) and / or wherein the algal growth rate at the end of step (b) is less than 0.6 d-1 (e.g. 0.5 d-1). In some embodiments, the series of connected raceway ponds in the first algal culture phase is a linear series. In some embodiments, the series of connected raceway ponds in the first algal culture phase comprises a first stage comprising one or more covered raceway ponds and a second stage comprising one or more stages of open raceway ponds. In some embodiments, one or more nutrient mineral acids are added during the first algal culture phase, optionally wherein the one or more nutrient mineral acids are selected from nitric acid, phosphoric acid and silicic acid. In some embodiments, the second algal culture phase is performed for at least four days (e.g. 4-10 days). In some embodiments, the carotene is alpha-carotene. In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Cryptophyta, Prasinophyceae, Chlorophyceae or Ulvophyceae. In some such embodiments, the marine carotenoid-producing microalgae are Cryptophyta or Chlorophyceae. The invention further provides methods of xanthophyll production, including methods of lutein, zeaxanthin and violaxanthin production. Xanthophylls Xanthophylls are one of the two major divisions of carotenoids. The other division is formed by the carotenes. While carotenes are purely hydrocarbons, xanthophylls contain oxygen atoms, typically as a hydroxyl group. The invention provides a method for producing a xanthophyll, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen), thereby inducing the algae to increase xanthophyll production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the xanthophyll from the algae harvested in step (c). In some embodiments, the extraction phase comprises extracting the xanthophyll from the algal slurry produced in step (c), wherein said extracting comprises: (i) suspending the algal slurry in an alkyl-ester solvent, (ii) separating the alkyl-ester solvent phase from the water phase, (ill) evaporating the alkyl-ester solvent to generate an oleoresin, wherein water is added before or during evaporation, (iv) saponifying the oleoresin to generate a slurry (that comprises carotene), (v) filtering the slurry to generate a filter cake (that comprises carotene), (vi) adding an organic non-ester solvent to the filtrate obtained in step (v), (vii) separating the water phase from the organic non-ester solvent phase, (viii) evaporating the organic non-ester solvent to generate an oleoresin that comprises the xanthophyll, and (ix) drying the oleoresin. In some embodiments, the alkyl-ester solvent in step d(i) is ethyl acetate. In some embodiments, the alkyl-ester solvent in step d(i) is food-grade ethyl acetate. In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as a concentrated alkali metal hydroxide solution (e.g. concentrated NaOH or KOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as NaOH (50 wt%), optionally to a final concentration of 0.5-5 M NaOH (e.g., 1-2.5 M NaOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as KOH (50 wt%), optionally to a final concentration of 0.5-5 M KOH (e.g., 1-2.5 M KOH). The organic non-ester solvent in step d(vi) preferably displays volatility and immiscibility with water. In addition, the solvent is preferably non-hydrolysable under basic conditions. In some embodiments, the organic non-ester solvent in step d(vi) is an aliphatic hydrocarbon. In some embodiments, the solvent is a food grade aliphatic hydrocarbon. In some embodiments, the organic non-ester solvent in step d(vi) is a monoterpene. In some embodiments, the solvent is a food grade monoterpene. In some embodiments, the organic non-ester solvent in step d(vi) is selected from hexane and limonene. In some embodiments, the organic non-ester solvent in step d(vi) is selected from food grade hexane and food grade limonene. In some embodiments, the organic non-ester solvent in step d(vi) is hexane. In some embodiments, the solvent is food grade hexane. In some embodiments, the organic non-ester solvent in step d(vi) is limonene. In some embodiments, the solvent is food grade limonene. In some embodiments, the organic non-ester solvent in step d(vi) is p-cymene. In some embodiments, the solvent is food grade p-cymene. In preferred embodiments, the extraction phase is performed under an inert gas (e.g., a nitrogen blanket). This prevents oxidation of the extracts. In some embodiments, the xanthophyll is lutein. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta (e.g., Dunaliella sp.) orChlorarachniophyta. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyceae, Trebouxiophyceae orCharophyceae. In some embodiments, the xanthophyll is diadinoxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Heterokontophyta (e.g., Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, or Xanthophyceae), Haptophyta, Dinophyta or Euglenophyta. In some such embodiments, the marine carotenoid-producing microalgae are Rhopalodiaceae sp. Hemiaulus sp., Climacodium sp., Skeletonema spp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp. In some embodiments, the xanthophyll is diadinoxanthin and the marine carotenoid-producing microalgae are Xanthophyceae, Haptophyta, Dinophyta or Euglenophyta. In some embodiments, the xanthophyll is zeaxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta, Chlorarachniophyta, Haptophyta, Dinophyta, Euglenophyta, Heterokontophyta (e.g., Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, or Xanthophyceae), Cryptophyta, unicellular Rhodophyta, Glaucophyta or Cyanophyta. In some such embodiments, the marine carotenoid-producing microalgae are (i) Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema spp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., (ii) Dunaliella sp. In some embodiments, the xanthophyll is zeaxanthin and the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Raphidophyceae or Phaeophyceae. In some embodiments, the xanthophyll is violaxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta (e.g., Dunaliella sp.), Chlorarachniophyta, or Heterokontophyta (e.g., Raphidophyceae, Phaeophyceae, or Eustigmatophyceae). In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae), Phaeophyceae or Eustigmatophyceae. In some embodiments, the xanthophyll is neoxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Euglenophyta, Chlorophyta (e.g., Dunaliella sp.) or Chlorarachniophyta. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae). In some embodiments, the xanthophyll is fucoxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Heterokontophyta (e.g., Chrysophyceae, Raphidophyceae, Bacillariophyceae, or Phaeophyceae), Haptophyta, or Dinophyta. In some such embodiments, the marine carotenoid-producing microalgae are Rhopalodiaceae sp. Hemiaulus sp., Climacodium sp., Skeletonema spp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp. In some embodiments, the xanthophyll is fucoxanthin and the marine carotenoid-producing microalgae are Chrysophyceae, Bacillariophyceae, Phaeophyceae or Haptophyta. In some embodiments, the xanthophyll is vaucheriaxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Heterokontophyta (e.g., Chrysophyceae or Eustigmatophyceae). In some embodiments, the xanthophyll is loroxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Euglenophyta, Chlorophyta (e.g., Prasinophyceae, Chlorophyceae or Ulvophyceae) or Chlorarachniophyta, In some embodiments, the xanthophyll is siphonaxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Euglenophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae or Ulvophyceae). In some such embodiments, the marine carotenoid-producing microalgae are Prasinophyceae. In some embodiments, the xanthophyll is one or more of nostoxanthin, echinenone, myxol glycosides and oscillol glycosides. In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta. In some embodiments, the xanthophyll is one or more of echinenone, myxol glycosides and oscillol glycosides. In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta. In some embodiments, the xanthophyll is one or more of alloxanthin, crocoxanthin and monadoxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Cryptophyta. In some embodiments, the xanthophyll is violaxanthin fatty acid ester. In some such embodiments, the marine carotenoid-producing microalgae are Heterokontophyta (e.g., Xanthophyceae), In some embodiments, the xanthophyll is fucoxanthin fatty acid ester. In some such embodiments, the marine carotenoid-producing microalgae are Haptophyta. In some embodiments, the xanthophyll is peridinin. In some such embodiments, the marine carotenoid-producing microalgae are Dinophyta. In some embodiments, the xanthophyll is prasinoxanthin. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta (e.g., Prasinophyceae), In some embodiments, the xanthophyll is loroxanthin fatty acid ester. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta (e.g., Prasinophyceae) or Chlorarachniophyta. In some embodiments, the xanthophyll is siphonaxanthin fatty acid ester. In some such embodiments, the marine carotenoid-producing microalgae are Chlorophyta (e.g., Prasinophyceae, Chlorophyceae or Ulvophyceae). In some such embodiments, the marine carotenoid-producing microalgae are Prasinophyceae or Ulvophyceae. In some embodiments, the marine carotenoid-producing microalgae are Cyanophyta. In some such embodiments, the xanthophyll is one or more of zeaxanthin, nostoxanthin, echinenone, myxol glycosides and oscillol glycosides. In some such embodiments, the xanthophyll is one or more of zeaxanthin, echinenone, myxol glycosides and oscillol glycosides. In some embodiments, the marine carotenoid-producing microalgae are Glaucophyta. In some such embodiments, the xanthophyll is zeaxanthin. In some embodiments, the marine carotenoid-producing microalgae are Rhodophyta. In some such embodiments, the xanthophyll is zeaxanthin. In some embodiments, the marine carotenoid-producing microalgae are Cryptophyta. In some such embodiments, the xanthophyll is one or more of alloxanthin, crocoxanthin and monadoxanthin. In some embodiments, the marine carotenoid-producing microalgae are Chrysophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, diatoxanthin, diadinoxanthin, fucoxanthin and vaucheriaxanthin. In some such embodiments, the xanthophyll is fucoxanthin. In some embodiments, the marine carotenoid-producing microalgae are Raphidophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin, diatoxanthin, diadinoxanthin and fucoxanthin. In some such embodiments, the xanthophyll is zeaxanthin. In some embodiments, the marine carotenoid-producing microalgae are Bacillariophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, diatoxanthin, diadinoxanthin and fucoxanthin. In some such embodiments, the xanthophyll is fucoxanthin. In some embodiments, the marine carotenoid-producing microalgae are Phaeophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin, diatoxanthin, diadinoxanthin and fucoxanthin. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin and fucoxanthin. In some embodiments, the marine carotenoid-producing microalgae are Xanthophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, diatoxanthin, diadinoxanthin and violaxanthin fatty acid ester. In some such embodiments, the xanthophyll is one or more of diatoxanthin and diadinoxanthin. In some embodiments, the marine carotenoid-producing microalgae are Eustigmatophyceae. In some such embodiments, the xanthophyll is one or more of violaxanthin and vaucheriaxanthin. In some such embodiments, the xanthophyll is violaxanthin. In some embodiments, the marine carotenoid-producing microalgae are Haptophyta. In some such embodiments, the xanthophyll is one or more of zeaxanthin, diatoxanthin, diadinoxanthin, fucoxanthin and fucoxanthin fatty acid ester. In some such embodiments, the xanthophyll is one or more of diadinoxanthin and fucoxanthin. In some embodiments, the marine carotenoid-producing microalgae are Dinophyta. In some such embodiments, the xanthophyll is one or more of zeaxanthin, diatoxanthin, diadinoxanthin, fucoxanthin and peridinin. In some such embodiments, the xanthophyll is one or more of diadinoxanthin and peridinin. In some embodiments, the marine carotenoid-producing microalgae are Euglenophyta. In some such embodiments, the xanthophyll is one or more of zeaxanthin, neoxanthin, diatoxanthin, diadinoxanthin, loroxanthin and siphonaxanthin. In some such embodiments, the xanthophyll is diadinoxanthin. In some embodiments, the marine carotenoid-producing microalgae are Chlorarachniophyta. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin, neoxanthin, lutein, loroxanthin and loroxanthin fatty acid ester. In some embodiments, the marine carotenoid-producing microalgae are Prasinophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin, neoxanthin, lutein, loroxanthin, siphonaxanthin, prasinoxanthin, loroxanthin fatty acid ester and siphonaxanthin fatty acid ester. In some such embodiments, the xanthophyll is one or more of violaxanthin, neoxanthin, siphonaxanthin and siphonaxanthin fatty acid ester. In some embodiments, the marine carotenoid-producing microalgae are Chlorophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin, neoxanthin, lutein, loroxanthin, siphonaxanthin and and siphonaxanthin fatty acid ester. In some such embodiments, the xanthophyll is one or more of violaxanthin, neoxanthin and lutein. In some embodiments, the marine carotenoid-producing microalgae are Ulvophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin, neoxanthin, lutein, loroxanthin, siphonaxanthin and siphonaxanthin fatty acid ester. In some such embodiments, the xanthophyll is one or more of violaxanthin, neoxanthin and siphonaxanthin fatty acid ester. In some embodiments, the marine carotenoid-producing microalgae are Trebouxiophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin, neoxanthin and lutein. In some such embodiments, the xanthophyll is one or more of violaxanthin, neoxanthin and lutein. In some embodiments, the marine carotenoid-producing microalgae are Charophyceae. In some such embodiments, the xanthophyll is one or more of zeaxanthin, violaxanthin, neoxanthin and lutein. In some such embodiments, the xanthophyll is one or more of violaxanthin, neoxanthin and lutein. The invention further provides a method for producing a xanthophyll, wherein the method comprises: (d) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of the presence of high salinity (e.g. at least 40 parts per thousand (%o)), thereby inducing the algae to increase xanthophyll production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the xanthophyll from the algae harvested in step (c). The invention further provides a method for producing a xanthophyll, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) at a low temperature (e.g. less than 20°C), thereby inducing the algae to increase xanthophyll production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the xanthophyll from the algae harvested in step (c). The examples demonstrate the production of an exemplary xanthophyll, lutein. In view of the structural similarity between lutein and other marine microalgae-produced xanthophylls, the lutein production methods described herein are broadly applicable to xanthophylls in general, and the specific xanthophylls discussed above. Lutein production The invention provides a method for producing lutein, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine lutein-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen), thereby inducing the algae to increase lutein production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the lutein from the algae harvested in step (c). In some embodiments, the extraction phase comprises extracting the lutein from the algal slurry produced in step (c), wherein said extracting comprises: (i) suspending the algal slurry in an alkyl-ester solvent, (ii) separating the alkyl-ester solvent phase from the water phase, (iii) evaporating the alkyl-ester solvent to generate an oleoresin, wherein water is added before or during evaporation, (iv) saponifying the oleoresin to generate a slurry, (v) filtering the slurry to generate a filter cake, (vi) adding an organic non-ester solvent to the filtrate obtained in step (v), (vii) separating the water phase from the organic non-ester solvent phase, (viii) evaporating the organic non-ester solvent to generate an oleoresin that comprises the lutein, and (ix) drying the oleoresin. In some embodiments, the alkyl-ester solvent in step d(i) is ethyl acetate. In some embodiments, the alkyl-ester solvent in step d(i) is food-grade ethyl acetate. In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as a concentrated alkali metal hydroxide solution (e.g. concentrated NaOH or KOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as NaOH (50 wt%), optionally to a final concentration of 0.5-5 M NaOH (e.g., 1-2.5 M NaOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as KOH (50 wt%), optionally to a final concentration of 0.5-5 M KOH (e.g., 1-2.5 M KOH). The organic non-ester solvent in step d(vi) preferably displays volatility and immiscibility with water. In addition, the solvent is preferably non-hydrolysable under basic conditions. In some embodiments, the organic non-ester solvent in step d(vi) is an aliphatic hydrocarbon. In some embodiments, the solvent is a food grade aliphatic hydrocarbon. In some embodiments, the organic non-ester solvent in step d(vi) is a monoterpene. In some embodiments, the solvent is a food grade monoterpene. In some embodiments, the organic non-ester solvent in step d(vi) is selected from hexane and limonene. In some embodiments, the organic non-ester solvent in step d(vi) is selected from food grade hexane and food grade limonene. In some embodiments, the organic non-ester solvent in step d(vi) is hexane. In some embodiments, the solvent is food grade hexane. In some embodiments, the organic non-ester solvent in step d(vi) is limonene. In some embodiments, the solvent is food grade limonene. In some embodiments, the organic non-ester solvent in step d(vi) is p-cymene. In some embodiments, the solvent is food grade p-cymene. In preferred embodiments, the extraction phase is performed under an inert gas (e.g., a nitrogen blanket). This prevents oxidation of the extracts. In some embodiments, the marine lutein-producing microalgae are Chlorophyta (e.g., Dunaliella sp.) orChlorarachniophyta. In some such embodiments, the lutein carotenoid-producing microalgae are Chlorophyceae, Trebouxiophyceae or Charophyceae.The invention further provides a method for producing lutein, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine lutein-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of the presence of high salinity (e.g. at least 40 parts per thousand (%o)), thereby inducing the algae to increase lutein production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the lutein from the algae harvested in step (c). The invention provides a method for producing lutein, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine lutein-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) at a low temperature (e.g. less than 20°C), thereby inducing the algae to increase lutein production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the lutein from the algae harvested in step Zeaxanthin production The invention provides a method for producing zeaxanthin, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine zeaxanthin-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen), thereby inducing the algae to increase zeaxanthin production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the zeaxanthin from the algae harvested in step (c). In some embodiments, the extraction phase comprises extracting the zeaxanthin from the algal slurry produced in step (c), wherein said extracting comprises: (i) suspending the algal slurry in an alkyl-ester solvent, (ii) separating the alkyl-ester solvent phase from the water phase, (iii) evaporating the alkyl-ester solvent to generate an oleoresin, wherein water is added before or during evaporation, (iv) saponifying the oleoresin to generate a slurry, (v) filtering the slurry to generate a filter cake, (vi) adding an organic non-ester solvent to the filtrate obtained in step (v), (vii) separating the water phase from the organic non-ester solvent phase, (viii) evaporating the organic non-ester solvent to generate an oleoresin that comprises the zeaxanthin, and (ix) drying the oleoresin. In some embodiments, the alkyl-ester solvent in step d(i) is ethyl acetate. In some embodiments, the alkyl-ester solvent in step d(i) is food-grade ethyl acetate. In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as a concentrated alkali metal hydroxide solution (e.g. concentrated NaOH or KOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as NaOH (50 wt%), optionally to a final concentration of 0.5-5 M NaOH (e.g., 1-2.5 M NaOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as KOH (50 wt%), optionally to a final concentration of 0.5-5 M KOH (e.g., 1-2.5 M KOH). The organic non-ester solvent in step d(vi) preferably displays volatility and immiscibility with water. In addition, the solvent is preferably non-hydrolysable under basic conditions. In some embodiments, the organic non-ester solvent in step d(vi) is an aliphatic hydrocarbon. In some embodiments, the solvent is a food grade aliphatic hydrocarbon. In some embodiments, the organic non-ester solvent in step d(vi) is a monoterpene. In some embodiments, the solvent is a food grade monoterpene. In some embodiments, the organic non-ester solvent in step d(vi) is selected from hexane and limonene. In some embodiments, the organic non-ester solvent in step d(vi) is selected from food grade hexane and food grade limonene. In some embodiments, the organic non-ester solvent in step d(vi) is hexane. In some embodiments, the solvent is food grade hexane. In some embodiments, the organic non-ester solvent in step d(vi) is limonene. In some embodiments, the solvent is food grade limonene. In some embodiments, the organic non-ester solvent in step d(vi) is p-cymene. In some embodiments, the solvent is food grade p-cymene. In preferred embodiments, the extraction phase is performed under an inert gas (e.g., a nitrogen blanket). This prevents oxidation of the extracts. In some embodiments, the marine zeaxanthin-producing microalgae are Chlorophyta, Chlorarachniophyta, Haptophyta, Dinophyta, Euglenophyta, Heterokontophyta (e.g., Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, orXanthophyceae), Cryptophyta, unicellular Rhodophyta, Glaucophyta or Cyanophyta. In some such embodiments, the zeaxanthin carotenoidproducing microalgae are (i) Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema spp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., (ii) Dunaliella sp. The invention further provides a method for producing zeaxanthin, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine zeaxanthin-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of the presence of high salinity (e.g. at least 40 parts per thousand (%o)), thereby inducing the algae to increase zeaxanthin production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the zeaxanthin from the algae harvested in step (c). The invention further provides a method for producing zeaxanthin, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine zeaxanthin-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) at a low temperature (e.g. less than 20°C), thereby inducing the algae to increase zeaxanthin production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the zeaxanthin from the algae harvested in step (c). Violaxanthin production The invention provides a method for producing violaxanthin, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine violaxanthin-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen), thereby inducing the algae to increase violaxanthin production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the violaxanthin from the algae harvested in step (c). In some embodiments, the extraction phase comprises extracting the violaxanthin from the algal slurry produced in step (c), wherein said extracting comprises: (i) suspending the algal slurry in an alkyl-ester solvent, (ii) separating the alkyl-ester solvent phase from the water phase, (iii) evaporating the alkyl-ester solvent to generate an oleoresin, wherein water is added before or during evaporation, (iv) saponifying the oleoresin to generate a slurry, (v) filtering the slurry to generate a filter cake, (vi) adding an organic non-ester solvent to the filtrate obtained in step (v), (vii) separating the water phase from the organic non-ester solvent phase, (viii) evaporating the organic non-ester solvent to generate an oleoresin that comprises the violaxanthin, and (ix) drying the oleoresin. In some embodiments, the alkyl-ester solvent in step d(i) is ethyl acetate. In some embodiments, the alkyl-ester solvent in step d(i) is food-grade ethyl acetate. In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as a concentrated alkali metal hydroxide solution (e.g. concentrated NaOH or KOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as NaOH (50 wt%), optionally to a final concentration of 0.5-5 M NaOH (e.g., 1-2.5 M NaOH). In some embodiments, step (d)(iv) is performed by adding concentrated alkali solution, such as KOH (50 wt%), optionally to a final concentration of 0.5-5 M KOH (e.g., 1-2.5 M KOH). The organic non-ester solvent in step d(vi) preferably displays volatility and immiscibility with water. In addition, the solvent is preferably non-hydrolysable under basic conditions. In some embodiments, the organic non-ester solvent in step d(vi) is an aliphatic hydrocarbon. In some embodiments, the solvent is a food grade aliphatic hydrocarbon. In some embodiments, the organic non-ester solvent in step d(vi) is a monoterpene. In some embodiments, the solvent is a food grade monoterpene. In some embodiments, the organic non-ester solvent in step d(vi) is selected from hexane and limonene. In some embodiments, the organic non-ester solvent in step d(vi) is selected from food grade hexane and food grade limonene. In some embodiments, the organic non-ester solvent in step d(vi) is hexane. In some embodiments, the solvent is food grade hexane. In some embodiments, the organic non-ester solvent in step d(vi) is limonene. In some embodiments, the solvent is food grade limonene. In some embodiments, the organic non-ester solvent in step d(vi) is p-cymene. In some embodiments, the solvent is food grade p-cymene. In preferred embodiments, the extraction phase is performed under an inert gas (e.g., a nitrogen blanket). This prevents oxidation of the extracts. In some embodiments, the marine violaxanthin-producing microalgae are Chlorophyta (e.g., Dunaliella sp.), Chlorarachniophyta, or Heterokontophyta (e.g., Raphidophyceae, Phaeophyceae, or Eustigmatophyceae). In some such embodiments, the marine carotenoidproducing microalgae are Chlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae), Phaeophyceae or Eustigmatophyceae. The invention provides a method for producing violaxanthin, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine violaxanthin-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) in the presence of the presence of high salinity (e.g. at least 40 parts per thousand (%o)), thereby inducing the algae to increase violaxanthin production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the violaxanthin from the algae harvested in step (c). The invention provides a method for producing violaxanthin, wherein the method comprises: (a) a first algal culture phase, wherein the first algal culture phase comprises culturing marine violaxanthin-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition; (b) a second algal culture phase, wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a), wherein the algae are cultured: (i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and (ii) at a low temperature (e.g. less than 20°C), thereby inducing the algae to increase violaxanthin production; (c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and (d) an extraction phase, wherein the extraction phase comprises extracting the violaxanthin from the algae harvested in step (c). Raceway ponds Land-based mariculture according to the invention comprises culturing algae in at least one raceway pond 100. Preferably the cultivation water for the at least one raceway pond 100 comprises seawater, but other types of water may be used, as discussed herein. Atypical raceway pond is illustrated in Figure 1. Raceway pond 100 is stadium shaped (i.e., a rectangle with semicircles at a pair of opposite ends), with a partial divide in the centre of the pond 100 (i.e., along the longitudinal axis A) to create a circuit (i.e., channel 120) having two longitudinal channel sections 120a, 120b which are joined at opposite ends of the raceway pond 100 by U-bend channel sections 120c, 120d. The stadium shape is defined by side wall 102. The partial divide is defined by divider 104. The side wall 102 and divider 104 may be formed of plastic covered and reinforced walls, fencing posts or earthen berms. Water and algae is retained in the raceway pond 100 by the side wall 102 and the base of the pond (not shown). At one side of divider 104 (e.g., along a side wall 102) there may be a support structure that serves both as an anchor for a paddlewheel 110 and to anchor the divider 104 between the longitudinal channel sections 120a, 120b. Paddlewheel 110 maintains the flow of water and algae around the circuit. The paddlewheel 110 is typically a variable speed paddlewheel. At the opposite ends of the raceway pond 100 (i.e., at the semicircles of the stadium shape), the channel has U-bend channel sections 120c, 120d. Within the U-bend channel sections 120c, 120d, there are flow diverters 106 to ensure efficient flow throughout the raceway. In particular, flow diverters 106 act to maintain laminar flow of algae and water around the channel 120, especially at the U-bend channel sections 120c, 120d. The raceway pond 100 further comprises an inlet pipe 108 and a drainpipe 112. The inlet pipe 108 may be connected to a gate-controlled sluice (not shown) for pond intake from either a seawater canal and / or a previous pond. The drainpipe 112 facilitates pond discharge through a second gate-controlled sluice (not shown). The dilution rate of the algae in the raceway pond 100, which is the rate at which water is added to the algae (i.e., to dilute the algae), is determined by the position of the gate-controlled sluice of the inlet pipe 108 and / or the drainpipe 112. For instance, opening the gate-controlled sluice of the inlet pipe 108 and closing the gate-controlled sluice of the drainpipe 112 increases the dilution rate. The dilution volume is the volume of water added to the raceway pond. In one embodiment, raceway pond 100 may be a covered raceway pond, which is a raceway pond 100 covered by a greenhouse (not shown). The primary purpose of the greenhouse is to protect the seed algae from being contaminated by windborne or bird-borne contaminants. Secondly the greenhouse is used to raise the temperature of the algal growth environment; both to increase the algal growth rate, and to inactivate competing or deleterious organisms that might otherwise contaminate the algae or foul the equipment. The greenhouse can also be used to selectively shade or change the illumination colour of the algae to induce a desirable physiological state by altering the wavelength of light. In one specific embodiment, every raceway pond 100 is covered by a greenhouse. Alternatively, raceway pond 100 may be an open raceway pond. An open raceway pond has no external cover, and as such is fully exposed to the ambient atmosphere, while a covered raceway pond (which may be fully or partially covered) allows partial or complete control of the temperature and light environment. Each raceway pond 100 is able to hold a certain volume of water and algae, depending on the depth, width and length of the raceway pond 100. In the context of the invention, volume of a raceway pond is defined as its capacity (i.e., the volume of fluid a raceway pond is capable of holding) ratherthan the volume of fluid actually held in the raceway pond at any given time. An increase in volume of raceway pond 100 is achieved by increased width and / or length of the raceway pond. In a specific embodiment, raceway pond 100 increases in volume through increased width and length. Depth of the raceway pond 100 cannot be increased as easily since changing the depth affects algal solar irradiation. In a specific embodiment, raceway pond 100 has a width (perpendicular to axis A) to length (along axis A) size ratio of between 1:4 and 1:12, preferably 1:8. At this ratio, there is relatively low head loss at each paddlewheel 110 as the water circulates around the bends, favourable economy of the construction materials (straight walls are easier to build than the bends), the reduction of wind influence (wind fetch) as it blows across the pond (to prevent potentially unmixed zones). The width of approximately 30 metres per channel 120 also reduces meandering flow to maintain turbulent flow. Information regarding the application of computational fluid dynamics to raceway pond design can be found in Kusmayadi, 2020. In some embodiments, a plurality of raceway ponds 100 may be used in parallel to increase the collective volume of water and algae. The plurality of raceway ponds 100 may form a group. The group may comprise, for example, 2, 4, 6, 8,10,12, 14, 16, or 18 ponds. The inlet pipe 108 of each raceway pond 100 of the group may connected to a common seawater canal. Similarly, the drainpipe 112 of each raceway pond 100 of the group may connected to a common outlet. In one embodiment, a covered raceway pond (or group of covered raceway ponds) has volume of between 50 I and 15,000,000 I, for example between 50 I and 50,000 I. In a particular embodiment, there is a series of covered raceway ponds, and the volume of covered raceway ponds in the series increases such that there is at least one pond in the series with a volume of (a) 50-1,000 I; at least one covered raceway pond in the series with a volume of (b) 100 1-30,000 I; and at least one pond in the series with a volume of (c) 5,000 - 12,000,000 I. In one embodiment, these ponds are linked in a linear fashion, such that there is one pond at each stage in the series. In one embodiment, an open raceway pond (or group of open raceway ponds) has volume of between 1,500,000 I and 3,000,000 I, in a further embodiment between 6,000,000 I and 15,000,000 I. In a still further embodiment, the volume of the open raceway ponds in the series increases such that there is at least one open raceway pond in the series with a volume of (a) 360,000 - 720,000 I; at least one pond in the series with a volume of (b) 1,500,000 - 3,000,000 I; and at least one pond in the series with a volume of (c) 6,000,000 - 15,000,000 I. As mentioned, paddlewheel 110 may be used to maintain the flow of the algae and water around the raceway pond 100. This is energy efficient whilst ensuring thorough mixing and the exposure of the algae to relatively low shear. This enables effective exchange of gases within the ambient air with the algae growth medium. According to the species being cultivated, paddlewheel 100 may be used to achieve a different flow rate of algae and water within a raceway pond based on the physical attributes of the paddlewheel (e.g., number of paddles, size of paddles) and / or the paddlewheel speed (i.e., its rotational speed). The flow rate may be 0.1-0.5 m / minute, e.g., 0.1-0.4 m / minute or 0.1-0.3 m / minute. In one embodiment, each raceway pond 100 has one or more paddlewheels 110 depending on the degree of agitation that is required. Preferably, each raceway pond 100 has one paddlewheel 110. The paddlewheel 110 may be positioned at any section of the raceway pond, but is preferably positioned close to the inlet pipe 108 of a raceway pond (e.g., where the rectangle section of the stadium shape transitions to a semicircle). In one embodiment, one or more paddlewheels 110 maintain the flow of the algae and water within raceway pond 100 at a rate of about 0.1-0.5 m / minute, for example 0.1-0.4 m / minute, or 0.1-0.3 m / minute, or 0.15 m / minute, 0.2 m / minute, 0.25 m / minute. The depth of raceway pond 100 affects algal solar irradiation. Both light intensity and wavelengths are altered by increasing water depth. In general, far red, red and ultraviolet light are absorbed the most rapidly by the water and a blue and green light penetrate the furthest. However, algae in a shallower raceway pond 100 experiences greater light intensity and a greater proportion of red light than algae in a deeper raceway pond 100. In one embodiment, raceway pond 100 is between 0.05 m and 10 m deep, for example, 0.05 m, 0.10 m, 0.20 m, 0.30 m, 0.40 m, 0.50m, 0.60 m, 0.70 m, 0.80 m, 0.90 m, 1 m, 1.5m, 2 m, 3 m, 5 m, or 10 m deep. In one embodiment, a covered raceway pond is 0.1 m - 1 m deep, for example 0.1 m, 0.2m, 0.3m, 0.4m, or 0.5m deep. In one embodiment, an open raceway pond is 0.25 or 0.3 m - 1 m deep, for example 0.25 m, 0.3 - 0.4m, 0.5 m, 0.75 or 1 m deep. Preferably an open raceway pond is less than 1 m deep. At this depth there is sufficient outgassing of O2 to help reduce oxidative stress, also at this depth there is sufficient exposure to dissolve atmospheric CO2. Raceway ponds known in the art are also usually uniform in depth. However, if the depth of raceway pond 100 is varied along the length of channel 120 (e.g., between longitudinal channel sections 120a, 120b), a change in the flow rate results. Furthermore, the exposure of the algae to solar irradiation is varied, with algae in shallower areas of the raceway pond experiencing greater light intensity and a greater proportion of red light than algae in deeper areas. Photosynthetic output can be affected by the light ratio, especially at dawn and dusk, and as discussed herein the depth of the water alters the light wavelength ratio. Thus, in one embodiment, the depth of raceway pond 100 is non-uniform, resulting in a change in algal exposure to light both in terms of light intensity and light wavelength ratio and / or a change in the rate of gas exchange within the non-uniform section of the raceway pond. In one embodiment, the difference between the depth in longitudinal channel sections 120a, 120b is 0.05-1.0 m, for example 0.05 m, 0.10 m, 0.2 m, 0.3 m, 0.4 m, 0.5 m, 0.6 m, 0.7 m, 0.8 m, 0.9 m or 1.0 m. For example, one longitudinal channel section 120a is 0.2-0.5 m deep, while the second longitudinal channel section 120b is 0.8-1.0 m deep. As described herein, raceway pond 100 may be lined (not shown). In one embodiment, raceway pond 100 is lined with an impermeable material. If seawater is used to culture the algae, a clay lining may be used to prevent saltwater intrusion onto the land. In one embodiment, a plastic waterproof lining is used instead of, or in addition to, a clay lining. In a particular embodiment, each raceway pond 100 is lined with 10-20 cm of clay and a 2-5 cm, e.g., about 3 cm or specifically 8,10 or 12 mm, robust synthetic liner such as a black or white geomembrane. A white coating, for instance from titanium oxide, may be provided over the black geomembrane. In one embodiment, the colour of the pond liners, or a coating of the pond liners, may be chosen to alter the wavelengths of light received by the algae as light reflects off the base of the ponds. The colour of the liner or coating may selectively decrease exposure of the algae to underwater red (630-680 nm), far red (700-750 nm) and / or blue (400-450 nm) light. In one embodiment, the liner or coating selectively decreases the exposure to underwater red (630-680 nm), far red (700-750 nm) and / or blue (400-450 nm) light by 10-90%, 20-80%, 30-70%, or 40-60%. For example, the liner or coating may selectively absorb upto 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100% of the incident underwater red (630-680 nm), far red (700-750 nm) and / or blue (400-450 nm) light before the remaining light is reflected through the algal growth environment again. This is achieved by selecting the colour of the pond liner or coating based on the wavelengths that are to be absorbed. In a preferred embodiment, the lining or coating is white in order to reflect light off the base of the pond and maximise the light available for photosynthesis and encourage algal growth especially in the low-density cultures and / or shallow cultures less than 30cm deep, where light will penetrate the depth of the medium. In some instances, black liners may be used to deliberately increase the temperature of the cultivation medium. Different colours of lining or coating may be used to induce different physiological effects in the algae. For example, the lining or coating may be entirely red, blue or green. Alternatively, a single stage in the sequence of ponds can be coloured blue, for example at the point where the seed algal growth has been synchronised in the initial covered ponds, to reinforce cellular growth synchronisation and increase growth before cell division, just before the cells are introduced into the open growth ponds so that multiple divisions then occur in the growth pond. Similarly, the growth pond can be lined or coated in blue to stimulate the migration of chloroplasts to the outside of the cells, to promote maximum photosynthesis (Kraml &Hermann, 1991; Furukawa et al., 1998). As an alternative to coloured lining or coating, the side wall 102, base and other structural features within the pond may be coloured. For instance, the side wall 102, base and other structural features may be white. Series of raceway ponds In one embodiment, the land-based mariculture of the invention comprises culturing algae in a series of connected raceway ponds, arranged in stages. Each of the raceway ponds in the series of connected raceway ponds may be based on raceway pond 100 of Figure 1. An example of an algal cultivation system 200 comprising a series of connected raceway ponds 210 arranged in stages 210A-230E is illustrated in Figure 2A. Figure 2B shows subsystem 200’ of system 200 in further detail. The stages 210A-230E of raceway ponds are connected in such a way so as to allow water and algae to pass directly between raceway ponds 100 in successive stages of the series. However, the connection between the stages 210A-230E of raceway ponds 100 can be closed and each stage 210A-230E of raceway ponds can be an isolated growth environment. The flow of water and algae between successive stages in the series is unidirectional, i.e., the passage of algae and water through the connected series of raceway ponds is one-way and algae and water are not recirculated. In particular, in Figures 2A and 2B, there are three stages of covered raceway ponds, 210A, 210B and 210C and two stages of open raceway ponds 210D, 210E. However, other numbers of stages of covered raceway ponds and open raceway ponds may be used. In one specific embodiment of the invention the series of connected raceway ponds 210 comprises firstly, one or more stages of covered raceway ponds 210A-210C and secondly, one or more stages of open raceway ponds 210D-210E. The designations of “firstly” one or more stages of covered raceway ponds 210A-210C and “secondly” one or more stages of open raceway ponds 21OD-210E indicate that within the series of connected ponds 210, the stages comprising covered raceway ponds 210A-210C will always come before the stages comprising open raceway ponds 21 OD-210E. Put another way, an open raceway 210A-210C pond will never be succeeded by a covered raceway pond 21 OD-210E. Each stage 210A-210E of the series of connected raceway ponds 210 may comprise one or more raceway ponds 100. Stages having a plurality (or group) of raceway ponds 100 use these ponds in parallel to increase the collective volume of water and algae that is throughput. The system 200 in Figures 2A and 2B, there are 16 ponds in each stage 210A-210E. However, the number of ponds does not have to be the same for each stage, as discussed further herein. In addition to the series of connected raceway ponds 210, system 200 comprises an intake pipeline 202 to transport water to the system, typically seawater from the ocean. Intake pipeline 202 feeds intake canal 208 which provides each of the raceway ponds in the series of connected raceway ponds 210 with water. Each raceway pond 100 has a connection to supply canal 208 at its respective inlet pipe 108. The supply canal 208 may be elevated so that gravity can be used to transport water to each of the raceway ponds 100 via the inlet pipe 108. The elevated supply canal filled from intake pipeline 202 with high-rate, low-head pumps. System 200 also comprises a harvest canal 212. Each raceway pond 100 in at least the final stage of the series of connected raceway ponds 210 has a connection to harvest canal 212 at its respective drain pipe 112. In stages other than the final stage, each raceway pond 100 is connected to the next stage of raceway ponds via its respective drainpipe 112. The harvest canal 212 leads to a harvesting building 214, where the algae is collected. The spent water is discharged through discharge pipeline 216. The discharge pipeline is at low elevation so that gravity moves water out of the harvesting building 214. In embodiments where the water is seawater, the intake pipeline 202 is upstream and as far needed from the discharge pipeline 216 to avoid reuptake of already spent seawater. Successive dilution in a semi-continuous cultivation manner, which maintains a low algal cell density, is beneficial for maintaining algae in the exponential growth phase. Successive dilution can be achieved in two ways. In the first way dilution Is achieved by increasing the collective volume of the raceway pond(s) 100 in each stage 210A-210E of the series. This increase in collective volume can be achieved by increasing the volume of the individual raceway ponds in each successive stage 210A-210E of the series and / or by increasing the number of raceway ponds in each successive stage 210A-210E of the series. Thus, at each successive stage 210A-210E in the series of raceway ponds 210 of the present invention, each individual raceway pond has a volume greater than the volume of the individual raceway ponds in the preceding stage of the series; and / or each raceway pond is immediately succeeded by a greater number of raceway ponds, wherein the collective volume of the raceway ponds in any given stage exceeds the collective volume of the raceway ponds of the preceding stage. In the second way, dilution is achieved by increasing the volume of water in discrete steps to a maximum volume within a raceway pond 100, before the water and algae are transferred to the subsequent larger pond(s). For example, each pond may be initially filled to a first volume having a first depth (e.g., 0.25 m) where the cells complete a growth cycle. When it is time to increase (e.g., double) the volume of the water, to enable the cells to grow at a low standing stock with natural nutrients, the volume of water of the same pond is increased to a second volume having a second depth (e.g., 0.5 m). After the second growth cycle is complete within that pond, the total volume of the two division stages and the water is transferred to the next larger, subsequent pond. In other embodiments, the pond is filled in subsequent stages to 0.25 m, 0.5 m, 0.75 m and 1 m depth in four sequential ‘within-pond’ dilutions before it is transferred to the next larger pond. This ‘stacking’ of ponds is possible because of the relatively low standing stock (or low cellular concentration) of the algae in comparison to other cultivation systems. In other commercial algal growth systems (where cells are grown at a density resulting between 1,000 - 2,000 mg Chi a m-3), the high cell density results in gas exchange limitations and self-shading. However, in this method, neither of these are critical concerns, because the cell densities are significantly lower for the first 12-16 growth cycles resulting in 50, 100, 200, 300, 400, 500 mg Chi a nr3). At these Chi a concentrations the ponds can be run without cell shading and the natural capacity of the seawater to absorb and buffer gases as well as exchange gases with the atmosphere enables cell growth. When algae and water are transferred from a raceway pond (covered or open) in one stage of the series to one or more raceway ponds (covered or open) in the next stage of the series, either the algae and water are transferred to a single raceway pond with a greater volume, or the algae and water are divided between a number of raceway ponds with a larger collective volume. Each transfer of the algae and water from one stage of the series to the next stage in the series thus involves dilution of the algae or is preceded by dilution of the algae in the current stage of ponds. In one embodiment, when the algae and water from one stage in the series (e.g., stage 210A) is used to seed the raceway pond or raceway ponds of the next stage (e.g., stage 210B), it is transferred to the raceway pond or raceway ponds of larger volume in the next stage of the series. Water is added to, or is already present in, the raceway ponds to be seeded, such that the final volume of fluid within the raceway ponds after seeding is equal to its capacity. This seeding step results in the algae being diluted and a low algal cell density can thus be maintained. Maintaining this constant low cell density of algae prevents the problems associated with traditional high-density algal culture, such as quorum sensing, biofilm formation and other (often unpredictable) algal stress responses. In an alternative embodiment, the algae are diluted prior to being transferred to the next stage of ponds. In this embodiment, fresh seawater is added to the current stage of ponds to dilute the algae. The successive dilution of the algae at each seeding step should not be taken to mean that the algal cell density at each stage in the series is successively reduced. Since the algae multiply rapidly, despite the successive dilutions at each seeding step the approximate cell density of algae in each stage of raceway ponds 210A-210E going through the series may increase, decrease or remain the same. In a specific embodiment, there are at least two stages of covered raceway ponds in the series of connected raceway ponds. For example, there may be 2, 3, 4, 5, 6, 7, 8, 9,10,15 or 20 stages of covered raceway ponds. In one embodiment, there are 2-10 stages of covered raceway ponds, 4-8 stages of covered raceway ponds, or 5 stages of covered raceway ponds. In a preferred embodiment, the covered raceway ponds are preferably greenhouse covered and are connected in linear succession, wherein there is one covered raceway pond at each stage in the series of covered raceway ponds. In this embodiment, each covered raceway pond is at least 2 times, for example 2 to 5 times, the volume of the covered raceway pond of the previous stage in the series. In a specific embodiment, each covered raceway pond is 2, 3, 4, or 5 times volume of the covered raceway pond of the previous stage in the series. In a preferred embodiment, each covered raceway pond is 5 times volume of the covered raceway pond of the previous stage in the series. In a further specific embodiment, there are at least two stages of open raceway ponds in the series of connected raceway ponds. For example, there may be 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20 or 25 stages of open raceway ponds. In one embodiment, there are 2-10 stages of open raceway ponds, 4-6 stages of open raceway ponds, or 5 stages of open raceway ponds. In one specific embodiment, there are more open raceway ponds than closed raceway ponds in the series. In some embodiments, the number of open raceway ponds in each stage is the same for each successive stage in the series. For example, the system 200 in Figure 2A and 2B has 16 ponds in the first stage of covered raceway ponds 210A, 16 ponds in the second stage of covered raceway ponds 210B which are larger than the ponds in the first stage of covered raceway ponds 210A, 16 ponds in the third stage of covered raceway ponds 21OC which are larger than the ponds in the second stage of covered raceway ponds 21 OB. There is also 16 ponds in the first stage of open raceway ponds 21OD (fourth stage overall) which are larger than the ponds in the third stage of covered raceway ponds 21 OC, and 16 ponds in the second stage of open raceway ponds 21OE (fifth stage overall), which are larger than the ponds in the first stage of open raceway ponds 21 OE. Each subsequent pond has at least twice the capacity of the previous pond to hold the entirety of the volume of the previous pond and the equivalent volume of unused seawater. In a particular embodiment, the number of open raceway ponds in each stage increases at each successive stage in the series. In this embodiment, each open raceway pond is connected to two or more open raceway ponds in the next stage in the series, and the collective volume of each of the two or more open raceway pond exceeds the volume of the raceway pond in the preceding stage. Therefore, in this particular embodiment, the algae and water in one open raceway pond is diluted into two or more open raceway ponds when the algae and water are transferred between stages in the series. In a specific embodiment, the number of open raceway ponds in each stage of the series doubles. Therefore, in this embodiment the number of raceway ponds at each stage in the series increases exponentially. For example, the number of open raceway ponds at each stage increases as follows: 1, 2, 4, 8,16, 32, 64,128. In this embodiment, as the number of open raceway ponds at each stage increases, so does the volume of each individual raceway pond. In a preferred embodiment, the volume of the individual open raceway ponds in one stage is at least two times, preferably five times, the volume of the individual open raceway ponds in the previous stage. In an alternative embodiment, the volume of the individual open raceway ponds at each stage in the series remains the same, although the collective volume of the raceway ponds increases with each stage as the number of raceway ponds increases. The algae and water may be transferred between raceway ponds in successive stages of the series without any external force, for example it may be transferred under the influence of gravity. However, the algae and water will, on occasion when the local topography does not permit the use of gravity transfers, be pumped from one raceway pond to another, using any suitable pumping means that does not shear the cells. Figure 2A shows a particular layout for a series of connected raceway ponds 210. The advantage of this layout is that it efficiently hugs the coast along the edge of an ocean and enables each raceway pond to have at least one contact with the intake canal 208 and a discharge into the next larger and lower pond. This layout enables the water transfer within the entire pond system to rely on gravity feeds and requires a minimum of piping, while enabling easier maintenance of the ponds. This layout also takes advantage of the frequently encountered natural gradient along coastlines where distance from the shore commonly results in a slight increase in elevation. In some embodiments, the series comprises at least ten raceway ponds. In some embodiments, the series comprises at least fifteen raceway ponds. Seed ponds and photobioreactors In one embodiment, the first stage 21OA of covered raceway ponds is seeded with algae cultivated in a photobioreactor (PBR) 204 or a seed pond (not shown). The amount of algae that is used for seeding the initial pond at first stage 210A is referred to as the inoculum density. A PBR 204 achieves a highly controlled environment within the reactor to maintain an uncontaminated stock culture. In order to prevent contamination with competing organisms, bacterial and viral infection, or predatory organisms that reduce the yield or availability of the seed algae, PBR 204 preferably uses sand and membrane filtered, pre-treated and decontaminated seawater. The exchange of gases is carefully controlled, for example by sparging or bubbling CO2 into the reactor and removing excess O2. The addition of nutrients and the removal of waste products is also carefully controlled. Preferably, PBR 204 operates in a sterile environment. A seed pond (not shown) is an open or closed pond, preferably a closed raceway pond, in which the growth conditions for the algae can be controlled. The seed pond is used to grow a population of algae sufficient to seed the first stage 210A of covered raceway ponds. In one embodiment, the first stage 210A of covered raceway ponds is seeded with algae from a PBR 204 or seed pond in the early morning, e.g., from one hour before to two hours after dawn to enable the algae to exploit their new growth environment, right after they have divided in the predawn hours, for example 1-2 hours before dawn. In a particular embodiment, the first stage 210A of covered raceway ponds is seeded between 1-2 hours before and 1-2 hours after dawn, e.g., between 1 hour before and 2 hours after dawn, or in a specific embodiment when dawn is at 6 AM, the seeding occurs between the hours of 5 AM to 8 AM. Algae In some embodiments, a single species of algae is cultured. In some embodiments, more than one species of algae is cultured. In some embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Heterokontophyta, Haptophyta, Dinophyta, Euglenophyta, Chlorarachniophyta orChlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae orCharophyceae). In some such embodiments, the marine carotenoid-producing microalgae are Cyanophyta, Glaucophyta, unicellular Rhodophyta, Heterokontophyta, Haptophyta, Euglenophyta, Chlorarachniophyta orChlorophyta (e.g., Prasinophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae or Charophyceae). In some embodiments, the marine carotenoid-producing microalgae are: (i) Rhopalodiaceae sp., Hemiaulus sp., Cliinacodiurn sp., Skeletonema sp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., or (ii) Dunaliella sp.. In some embodiments, the marine carotenoid-producing microalgae are Dunaliella sp. In some such embodiments, the marine carotenoid-producing microalgae are Dunaliella salina. In some embodiments, the marine carotenoid-producing microalgae are Skeletonema sp. In some such embodiments, the marine carotenoid-producing microalgae are Skeletonema pseudocostatum. In some embodiments, the algae comprise diatom-diazotroph assemblages (DDAs). In some embodiments, the algae comprise diatoms. In some embodiments, the algae comprise bloom-forming algae. In some embodiments, the algae comprise r-strategist algae. DDAs In some embodiments, the algae that are cultured in the method of the invention comprise “diatom-diazotroph assemblages (DDAs)”. As used herein, “diatom-diazotroph assemblages (DDAs)” refers to symbioses between diatoms and diazotrophic prokaryotes. In these associations, the diazotrophic prokaryote captures or ‘fixes’ atmospheric N2 and makes it bioavailable to the diatom symbiont. In some embodiments, the DDAs comprise diazotrophic cyanobacteria. Diazotrophic cyanobacteria like Richelia, Calothrix and other unicellular species similar in morphology to free-living diazotroph Crocosphaera, thrive by forming symbiotic relationships with diatoms like Hemiaulus, Rhizosolenia, Chaetoceros and Climacodium (Mutalipassi etal., 2021; Hilton 2014). Some of these associations, like Calothrix or the novel unicellular cyanobacteria Candidatus Atelocyanobacterium thalassa (UCYN-A) (Tuo et al., 2017) associate with unicellular algae epiphytically (or on the outside of cells). Other diazotrophic symbionts are intracellular such as Richelia. In some embodiments, the DDAs comprise marine diazotrophic cyanobacteria. In some embodiments, the marine diazotrophic cyanobacteria are selected from Richelia sp., Calothrix sp., Crocosphaera sp. and Candidatus Atelocynaobacterium Thalassa. In some embodiments, the marine diazotrophic cyanobacteria are Richelia sp. In some embodiments, the marine diazotrophic cyanobacteria are Calothrix sp. In some embodiments, the marine diazotrophic cyanobacteria are Crocosphaera sp. In some embodiments, the marine diazotrophic cyanobacteria are Candidatus Atelocynaobacterium Thalassa. In some embodiments, the DDAs comprise Richelia sp., optionally R. intracellularis. In some embodiments, the DDAs comprise Calothrix sp., optionally one or more of C. adscendens, C. atricha, C. braunii, C. breviarticulata, C. caespitora, C. confervicola, C. Crustacea, C. donnelli, C. elenkinii, C. epiphytica, C. fusca, C. juliana, C. parasitica, C. parietina, C. pilosa, C. pulvinata, C. scopulorum, C. scytonemicola, C. simulans, C. solitaria, C. stagnalis, C. stellaris, and C. thermalis. In some embodiments, the DDAs comprise Crocosphaera sp., optionally C. watsonii. In some embodiments, the DDAs comprise one or more of the following diatoms: Hemiaulus sp., Skeletonema sp., Rhizosolenia sp., Climacodium sp. and Chaetoceros sp. In some embodiments, the DDAs comprise Hemiaulus sp., optionally H. hauckii, H. indicus, H. membranaceus, or H. sinensis. In some embodiments, the DDAs comprise Skeletonema sp., optionally S. barbadense, S. costatum, S. cylindraceum, S. mediterraneum, S. punctatum, S. tropicum, or S. pseudocostatum. In some embodiments, the DDAs comprise Rhizosolenia sp., optionally R. alata, R. acuminata, R. antarctica, R. antennata, R. bergonii, R. clevei, R. curvata, R. cylindrus, R. delicatula, R. minima, R. pugens, R. robusta, R. rothii, R. stricta, or R. styliformis. In some embodiments, the DDAs comprise Climacodiumsp., optionally C. biconcavum or C. frauenfeldianum. In some embodiments, the DDAs comprise Chaetoceros sp., optionally C. socialis, C. debilis, C. curvisetus, C. muelleri, C. calcitrans, or C. didymus. In some embodiments, the DDAs comprise an assemblage of marine diazotrophic cyanobacteria and diatoms. In some embodiments, the marine diazotrophic cyanobacteria are selected from Richelia sp., Calothrix sp., Crocosphaera sp. and Candidatus Atelocynaobacterium Thalassa, and the diatoms are selected from Hemiaulus sp., Skeletonema sp., Rhizosolenia sp., Climacodium sp. and Chaetoceros sp. In some embodiments, the DDAs comprise an assemblage of Richelia sp. and Hemiaulas sp. Oligotrophic conditions are nutrient poor conditions. For example, oligotrophic conditions may comprise low concentrations of bioavailable nitrogen and phosphorus. These oligotrophic conditions are preferably present within a raceway pond ora series of connected raceway ponds. In some instances, the oligotrophic conditions comprise less than 20 pM (e.g., 10 pM) phosphorus and less than 40 pM (e.g., 20 pM) nitrogen. Accordingly, in some embodiments of the invention, the algae comprise DDAs, and nutrient mineral acids are added to a total concentration of less than 60 pM (e.g., less than 30 pM). In some such embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the growth phase to a final concentration of less than 20 pM (e.g., less than 10 pM). In some such embodiments, nitrogen-containing acid (e.g., HNO3) is added in the growth phase to a final concentration of less than 40 pM (e.g., less than 20 pM). Diatoms In some embodiments, the algae that are cultured in the method of the invention comprise diatoms. In some embodiments, the diatoms are fast-growing diatoms. In some embodiments, the diatoms are bloom-forming diatoms. For example, diatoms that have (i) the ability to grow exponentially or (ii) a cell division rate that exceeds one division per day. In some embodiments, the diatoms are selected from Skeletonema sp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. and Nitzschia sp. In some embodiments, the diatoms are Skeletonema sp., optionally S. barbadense, S. costatum, S. cylindraceum, S. mediterraneum, S. punctatum, S. tropicum, or S. pseudocostatum. In some embodiments, the diatoms are Chaetoceros sp., optionally C. socialis, C. debilis, C. curvisetus, C. muelleri, C. calcitrans, or C. didymus. In some embodiments, the diatoms are Thalassiosira sp., optionally T. pseudonana, or T. symmetrica. In some embodiments, the diatoms are Coscinodiscus sp., optionally C. wailesii. In some embodiments, the diatoms are Navicula sp., optionally N. pelliculosa, N. incerta, N. oblonga, N. salinicola, N. ramosissima, N. minima, N. cryptocephala, or N. trivialis. In some embodiments, the diatoms are Synedra sp., optionally S. capitata, S. famelica, S. radians, S. rumpens, or S. ulna. In some embodiments, the diatoms are Nitzschia sp., optionally N. frigida, N. acicularis, N. amphibia, or N. angustata. Bloom-forming algae In some embodiments, the algae that are cultured in the method of the invention comprise bloom-forming algae. In some embodiments, the bloom-forming algae are Dunaliella sp., optionally D. salina. In some embodiments, the bloom-forming algae are Rhodomonas sp., optionally R. minuta. In some embodiments, the bloom-forming algae are Chaetoceros sp., optionally C. socialis, C. debilis, C. curvisetus, C. muelleri, C. calcitrans, C. didymus, or C. convolutus. R-strategist algae In ecology, r-strategist organisms are characterised by their high growth rates in less-crowded ecological niches. They are considered opportunistic organisms and thrive in more unstable and unpredictable environments due to their ability to reproduce rapidly. Conversely, K-strategist organisms are characterised by a much lower growth rate in an ecological niche which is close to or at the carrying capacity forthat organism. They exist in an equilibrium and thrive in more stable or predictable environments, competing for limited resources. The method of the invention described herein represents a controlled, stable and predictable environment in which algae are cultured. Algae often fit the description of r-strategist organisms, displaying rapid growth rates in often unstable and unpredictable environments. Therefore, it is surprising to find that algae grow particularly well in the tightly controlled, highly predictable conditions of the method of the invention described herein. In some embodiments, the algae that are cultured in the method of the invention comprise r-strategist algae. In some embodiments, the r-strategist algae are cultured in a K-strategist environment. In some embodiments, the r-strategist algae are cultured under K-strategist conditions. In some embodiments, K-strategist conditions comprise one or more of a stable temperature, a stable salinity level, a stable humidity and a stable duration of sunlight. Photosynthetically active radiation (PAR) As used herein, the term “photosynthetically active radiation” (PAR) refers to the range of wavelengths of light required for photosynthesis in algae. Typically, PAR is between 400 nm and 700 nm. As used herein, the term “light photoinhibition parameter” (Ekp) refers to a light level at which the growth rate of the algae begins to decrease. In a preferred embodiment, the mean photosynthetically active radiation (PAR) and UV light in each raceway pond and / or induction raceway pond does not exceed the light photoinhibition parameter (Ekp) of the algae. First algal culture phase The first algal culture phase comprises culturing marine carotenoid-producing microalgae in a series of connected raceway ponds, arranged in stages, wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition. As used herein, “nutrient mineral acid” refers to an inorganic acid in which the conjugate base provides nourishment for algae (e.g., the conjugate base is used by algae to survive and grow). In some embodiments, one or more nutrient mineral acids are added in the first algal culture phase. In some embodiments, the one or more nutrient mineral acids are selected from a phosphorus-containing acid, silicon-containing acid, and nitrogen-containing acid. In some embodiments, a phosphorus-containing acid is added in the first algal culture phase. In general, all algae assimilate phosphorus for survival and growth. Therefore, phosphorus-containing acids are nutritious for any algal species. In some embodiments, the nutrient mineral acid is a phosphorus oxoacid. In some embodiments, the nutrient mineral acid has a phosphate anion as a conjugate base. In some embodiments, the nutrient mineral acid is a phosphoric acid. In some embodiments, the phosphoric acid has the chemical formula H3PO4. In preferred embodiments, the phosphorus-containing acid is phosphoric acid (H3PO4). In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final concentration of at least 0.15 pM, at least 0.5 pM, at least 1.0 pM, at least 1.5 pM, at least 2.0 pM, at least 5.0 pM, at least 10 pM, or at least 15 pM. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final concentration of 0.15-15 pM (e.g., 0.5-4.5 pM, such as 1-2 pM). In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final concentration of between 0.1 pM and 2.0 pM, between 0.5 pM and 2.0 pM, or between 1.0 pM and 2.0 pM. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final concentration of 1.5 pM. The concentration of phosphorus-containing acid that is added can be influenced by the algal cell density. Accordingly, in some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 5 to (ii) number of thousand algal cells per ml multiplied by 25. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 7 to (ii) the number of thousand algal cells per ml multiplied by 15. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 10 to (ii) the number of thousand algal cells per ml multiplied by 13. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 5. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 10. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 12. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 15. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 20. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 25. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 5. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 10. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 12. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 15. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 20. In some embodiments, phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 25. In some embodiments, the phosphorous-containing conjugate base to the phosphorous-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final concentration of at least 0.15 pM, at least 0.5 pM, at least 1.0 pM, at least 1.5 pM, at least 2.0 pM, at least 5.0 pM, at least 10 pM, or at least 15 pM. In some embodiments, the phosphorous-containing conjugate base to the phosphorous-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final concentration of 0.15-15 pM (e.g., 0.5-4.5 pM, such as 1-2 pM). In some embodiments, the phosphorous-containing conjugate base to the phosphorous-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final concentration of between 0.1 pM and 2.0 pM, between 0.5 pM and 2.0 pM, or between 1.0 pM and 2.0 pM. In some embodiments, the phosphorous-containing conjugate base to the phosphorous-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final concentration of 1.5 pM. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 5 to (ii) number of thousand algal cells per ml multiplied by 25. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 7 to (ii) the number of thousand algal cells per ml multiplied by 15. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 10 to (ii) the number of thousand algal cells per ml multiplied by 13. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 5. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 10. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 12. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 15. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) Is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 20. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 25. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 5. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 10. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 12. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 15. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 20. In some embodiments, the phosphorous-containing conjugate base to the phosphorus-containing acid (e.g., H3PO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 25. In some embodiments, phosphorous is added in the first algal culture phase to a final concentration of at least 0.15 pM, at least 0.5 pM, at least 1.0 pM, at least 1.5 pM, at least 2.0 pM, at least 5.0 pM, at least 10 pM, or at least 15 pM. In some embodiments, phosphorous is is added in the first algal culture phase to a final concentration of 0.15-15 pM (e.g., 0.5-4.5 pM, such as 1-2 pM). In some embodiments, phosphorous is added in the first algal culture phase to a final concentration of between 0.1 pM and 2.0 pM, between 0.5 pM and 2.0 pM, or between 1.0 pM and 2.0 pM. In some embodiments, phosphorous is added in the first algal culture phase to a final concentration of 1.5 pM. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 5 to (ii) number of thousand algal cells per ml multiplied by 25. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 7 to (ii) the number of thousand algal cells per ml multiplied by 15. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 10 to (ii) the number of thousand algal cells per ml multiplied by 13. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 5. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 10. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 12. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 15. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 20. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 25. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 5. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 10. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 12. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 15. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 20. In some embodiments, phosphorus is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 25. In some embodiments, a silicon-containing acid is added in the first algal culture phase. Some algal species (e.g., diatoms) assimilate silicon as a component of their cell walls. Therefore, silicon-containing acids are nutritious for algal species with silica cell wells (e.g., diatoms). In some embodiments, the nutrient mineral acid has a silicate anion as a conjugate base. In some embodiments, the nutrient mineral acid is a silicic acid. In some embodiments, the nutrient mineral acid is orthosilicic acid, metasilicic acid, pyrosilicic acid or disilicic acid. In preferred embodiments, the silicon-containing acid is orthosilicic acid (H4SiO4). In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final concentration of at least 0.3 pM, at least 0.5 pM, at least 1.0 pM, at least 1.5 pM, at least 2.0 pM, at least 5.0 pM, at least 10 pM, at least 15 pM, or at least 30 pM. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final concentration of 0.3-30 pM (e.g., 1-9 pM, such as 2-4 pM). In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final concentration of between 0.3 pM and 5.0 pM, between 0.5 pM and 5 pM, between 1.0 pM and 5.0 pM, between 1.5 pM and 5.0 pM, between 2.0 pM and 5.0 pM, between 2.5 pM and 5.0 pM, between 2.5 pM and 4.5 pM, between 2.5 pM and 4.0 pM or between 2.5 pM and 3.5 pM. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final concentration of 3 pM. The concentration of silicon-containing acid (e.g., H4SiO4) that is added can be influenced by the algal cell density. Accordingly, in some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 5 to (ii) number of thousand algal cells per ml multiplied by 50. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 15 to (ii) the number of thousand algal cells per ml multiplied by 35. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 20 to (ii) the number of thousand algal cells per ml multiplied by 30. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 22 to (ii) the number of thousand algal cells per ml multiplied by 26. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 5. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 10. In some embodiments, silicon-containing acid (e.g, H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 15. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 20. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 25. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 30. In some embodiments, silicon-containing acid (e.g, H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 40. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 50. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 5. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 10. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 15. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 20. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 25. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 30. In some embodiments, silicon-containing acid (e.g, H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 40. In some embodiments, silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 50. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final concentration of at least 0.15 pM, at least 0.5 pM, at least 1.0 pM, at least 1.5 pM, at least 2.0 pM, at least 5.0 pM, at least 10 pM, or at least 15 pM. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final concentration of 0.15-15 pM (e.g., 0.5-4.5 pM, such as 1-2 pM). In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final concentration of between 0.1 pM and 2.0 pM, between 0.5 pM and 2.0 pM, or between 1.0 pM and 2.0 pM. In some embodiments, the final concentration of the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final concentration of 1.5 pM. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added In the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 5 to (ii) number of thousand algal cells per ml multiplied by 50. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 15 to (ii) the number of thousand algal cells per ml multiplied by 35. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 20 to (ii) the number of thousand algal cells per ml multiplied by 30. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 22 to (ii) the number of thousand algal cells per ml multiplied by 26. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 5. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 10. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 15. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 20. In some embodiments, the silicon- containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 25. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 30. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 40. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 50. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 5. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 10. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 15. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 20. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 25. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added In the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 30. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 40. In some embodiments, the silicon-containing conjugate base to the silicon-containing acid (e.g., H4SiO4) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 50. In some embodiments, silicon is added in the first algal culture phase to a final concentration of at least 0.15 pM, at least 0.5 pM, at least 1.0 pM, at least 1.5 pM, at least 2.0 pM, at least 5.0 pM, at least 10 pM, or at least 15 pM. In some embodiments, silicon is added in the first algal culture phase to a final concentration of 0.15-15 pM (e.g., 0.5-4.5 pM, such as 1-2 pM). In some embodiments, silicon is added in the first algal culture phase to a final concentration of between 0.1 pM and 2.0 pM, between 0.5 pM and 2.0 pM, or between 1.0 pM and 2.0 pM. In some embodiments, silicon is added in the first algal culture phase to a final concentration of 1.5 pM. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 5 to (ii) number of thousand algal cells per ml multiplied by 50. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 15 to (ii) the number of thousand algal cells per ml multiplied by 35. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 20 to (ii) the number of thousand algal cells per ml multiplied by 30. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 22 to (ii) the number of thousand algal cells per ml multiplied by 26. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 5. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 10. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 15. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 20. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 25. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 30. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 40. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 50. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 5. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 10. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 15. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 20. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 25. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 30. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 40. In some embodiments, silicon is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 50. In some embodiments, a nitrogen-containing acid is added in the first algal culture phase. Nitrogen-fixing algae (e.g., diatom-diazotroph assemblages) have a reduced requirement for assimilating nitrogen from the culture medium. Other algal species typically have a much greater need for nitrogen assimilation than for phosphorus assimilation from the culture medium. The average nitrogen to phosphorus ratio in algal biomass is 16:1. In some embodiments, the nutrient mineral acid is a nitrogen acid. In some embodiments, the nutrient mineral acid has a nitrate anion as a conjugate base. In some embodiments, the nutrient mineral acid is nitric acid, nitrous acid or hyponitrous acid. In preferred embodiments, the nitrogen-containing acid is nitric acid (HNOa). In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final concentration of at least 8 pM, at least 15 pM, at least 30 pM, at least 50 pM, at least 80 pM, at least 100 pM, at least 200 pM, at least 500 pM, or at least 800 pM. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final concentration of 8-800 pM (e.g., 20-320 pM, such as 60-100 pM). In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final concentration of between 50 pM and 100 pM, between 60 pM and 100 pM, between 70 pM and 100 pM, between 80 pM and 100 pM or between 80 pM and 90 pM. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final concentration of 80 pM. The concentration of nitrogen-containing acid (e.g., HNO3) that is added can be influenced by the algal cell density. Accordingly, in some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 50 to (ii) number of thousand algal cells per ml multiplied by 5000. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 200 to (ii) the number of thousand algal cells per ml multiplied by 1500. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 400 to (ii) the number of thousand algal cells per ml multiplied by 800. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 600 to (ii) the number of thousand algal cells per ml multiplied by 700. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 50. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 100. In some embodiments, nltrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 200. In some embodiments, nitrogencontaining acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 400. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 500. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 600. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 700. In some embodiments, nitrogencontaining acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 1000. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 2000. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 50. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 100. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 200. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 500. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 600. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 650. In some embodiments, nitrogencontaining acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 700. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 1000. In some embodiments, nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 2000. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final concentration of at least 8 pM, at least 15 pM, at least 30 pM, at least 50 pM, at least 80 pM, at least 100 pM, at least 200 pM, at least 500 pM, or at least 800 pM. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final concentration of 8-800 pM (e.g., 20-320 pM, such as 60-100 pM). In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final concentration of between 50 pM and 100 pM, between 60 pM and 100 pM, between 70 pM and 100 pM, between 80 pM and 100 pM or between 80 pM and 90 pM. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final concentration of 80 pM. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 50 to (ii) number of thousand algal cells per ml multiplied by 5000. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 200 to (ii) the number of thousand algal cells per ml multiplied by 1500. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 400 to (ii) the number of thousand algal cells per ml multiplied by 800. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 600 to (ii) the number of thousand algal cells per ml multiplied by 700. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 50. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 100. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 200. In some embodiments, the nitrogen-containing conjugate base to the nitrogencontaining acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 400. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNOs) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 500. In some embodiments, the nitrogencontaining conjugate base to the nitrogen-containing acid (e.g., HNOs) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 600. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 700. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 1000. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 2000. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 50. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 100. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 200. In some embodiments, the nitrogencontaining conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 500. In some embodiments, the nitrogen-containing conjugate base to the nitrogencontaining acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 600. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 650. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 700. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNOa) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 1000. In some embodiments, the nitrogen-containing conjugate base to the nitrogen-containing acid (e.g., HNO3) is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 2000. In some embodiments, nitrogen is added in the first algal culture phase to a final concentration of at least 8 pM, at least 15 pM, at least 30 pM, at least 50 pM, at least 80 pM, at least 100 pM, at least 200 pM, at least 500 pM, or at least 800 pM. In some embodiments, nitrogen is added in the first algal culture phase to a final concentration of 8-800 pM (e.g., 20-320 pM, such as 60-100 pM). In some embodiments, nitrogen is added in the first algal culture phase to a final concentration of between 50 pM and 100 pM, between 60 pM and 100 pM, between 70 pM and 100 pM, between 80 pM and 100 pM or between 80 pM and 90 pM. In some embodiments, nitrogen is added in the first algal culture phase to a final concentration of 80 pM. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 50 to (ii) number of thousand algal cells per ml multiplied by 5000. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 200 to (ii) the number of thousand algal cells per ml multiplied by 1500. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 400 to (ii) the number of thousand algal cells per ml multiplied by 800. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 600 to (ii) the number of thousand algal cells per ml multiplied by 700. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 50. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 100. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 200. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 400. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 500. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 600. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 700. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 1000. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as being at least the number of thousand algal cells per ml multiplied by 2000. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 50. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 100. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 200. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 500. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 600. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 650. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 700. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 1000. In some embodiments, nitrogen is added in the first algal culture phase to a final nanomolar concentration calculated as the number of thousand algal cells per ml multiplied by 2000. In some embodiments, one or more, two or more, three or more, four or more, or five or more nutrient mineral acids are added in the first algal culture phase. In some embodiments, the algae are diatoms, and a phosphorus-containing acid (e.g., H3PO4) a silicon-containing acid (H4SiO4), and a nitrogen-containing acid (e.g., HNO3) are added in the first algal culture phase. In some embodiments, the algae are diatom-diazotroph assemblages, and a phosphorus-containing acid (e.g., H3PO4) and a silicon-containing acid (H4SiO4) are added in the first algal culture phase. In some embodiments, the algae are bloom-forming algae, and a phosphorus-containing acid (e.g., H3PO4) and a nitrogen-containing acid (e.g., HNO3) are added in the first algal culture phase. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is at least 5 pM, at least 10 pM, at least 25 pM, at least 50 pM, at least 85 pM, at least 150 pM, at least 300 pM, at least 500 pM, or at least 850 pM. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is 5-850 pM (e.g., 25-150 pM, such as 80-90 pM). In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is between 50 and 100 pM, between 60 and 100 pM, between 70 and 100 pM, between 80 and 100 pM or between 80 and 90 pM. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being within the range of: (i) number of thousand algal cells per ml multiplied by 50 to (ii) number of thousand algal cells per ml multiplied by 5000. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 200 to (ii) the number of thousand algal cells per ml multiplied by 1500. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 400 to (ii) the number of thousand algal cells per ml multiplied by 800. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being within the range of: (i) the number of thousand algal cells per ml multiplied by 600 to (ii) the number of thousand algal cells per ml multiplied by 700. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 50. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 100. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 200. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 400. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 500. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 600. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 700. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 1000. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as being at least the number of thousand algal cells per ml multiplied by 2000. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 50. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 100. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 200. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 500. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 600. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 650. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 700. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 1000. In some embodiments, the final concentration of total nutrient mineral acid(s) after addition of nutrient mineral acid(s) is calculated as the number of thousand algal cells per ml multiplied by 2000. In some embodiments, nutrient mineral acids are added in the first algal culture phase to achieve a pH value in the range of pH6.5-7.5. In a preferred embodiment, the mean photosynthetically active radiation (PAR) and UV light in each raceway pond does not exceed the light photoinhibition parameter (Ekp) of the algae. In some embodiments, the algae are green during the first algal culture phase. In some embodiments, the algal growth rate during the first algal culture phase is at least 0.6d1. In some embodiments, the algal growth rate during the first algal culture phase is at least 0.7d-1. In some embodiments, the algal growth rate during the first algal culture phase is at least 0.8d-1. In some embodiments, the algal growth rate during the first algal culture phase is at least 0.9d-1. In a preferred embodiment, the algal growth rate during the first algal culture phase is at least 0.7d-1. Algal growth rate can be measured by cell density, dry weight biomass, live cell optical density, live cell fluorescence, solvent extracted pigment fluorescence or optical density, carbon content, turbidity or pond tonality via remote sensing imagery. For example, growth rate (p) may be calculated from the change in biomass from one time point (to) to a later time point (ti): p (d"1) = In some embodiments, the algal culture is diluted in each raceway pond in the first algal culture phase, and pond volume for each pond in the second algal culture phase is modelled by the following equation: Vi = Vo • wherein is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. The volume to dilute the pond can then be calculated as V1-V0. Conversely, if one wishes to target a final pond volume or harvest yield, and knows the growth rate at that pond stage, the equation can be modified where the target volume is divided by the exponent to calculate a starting pond volume. (-M 2 W2V This then sets the post-dilution volume for the upstream pond. This allows one to model an entire production system (in terms of pond stage volume) from either i), a starting volume, modelling the downstream ponds to a target final volume or ii), a final pond volume, modelling the upstream ponds to a target starting inoculum volume from the laboratory. In some embodiments, the series of connected raceway ponds in the first algal culture phase is a linear series. In some embodiments, the series of connected raceway ponds in the first algal culture phase comprises a first stage comprising one or more covered raceway ponds and a second stage comprising one or more open raceway ponds. Second algal culture phase The second algal culture phase comprises culturing algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in the first algal culture phase, wherein the algae are induced to produce carotene by culturing the algae with limited nutrients, high light exposure, high salinity, low temperature and / or reducing the dilution rate in the raceway pond, and / or culturing the algae in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds. As used herein, the term “induction raceway pond” refers to ponds in which the algae are induced to produce carotenoids. In some embodiments, the algae are induced to produce carotene by culturing the algae with limited nutrients. In some such embodiments, seawater is added to the raceway pond without nutrient supplementation. In some embodiments, the algae are induced to increase production of beta carotene by culturing the algae in the presence of a low concentration of nitrogen. In some embodiments, the concentration of nitrogen is less than 20 pM. In some embodiments, the concentration of nitrogen is less than 19 pM. In some embodiments, the concentration of nitrogen is less than 18 pM. In some embodiments, the concentration of nitrogen is less than 17 pM. In some embodiments, the concentration of nitrogen is less than 16 pM. In some embodiments, the concentration of nitrogen is less than 15 pM. In some embodiments, the concentration of nitrogen is less than 14 pM. In some embodiments, the concentration of nitrogen is less than 13 pM. In some embodiments, the concentration of nitrogen is less than 12 pM. In some embodiments, the concentration of nitrogen is less than 11 pM. In a preferred embodiment, the concentration of nitrogen is less than 10 pM. In some embodiments, the concentration of nitrogen is less than 9 pM. In some embodiments, the concentration of nitrogen is less than 8 pM. In some embodiments, the concentration of nitrogen is less than 7 pM. In some embodiments, the concentration of nitrogen is less than 8 pM. In some embodiments, the concentration of nitrogen is less than 6 pM. In some embodiments, the concentration of nitrogen is less than 5 pM. In some embodiments, the algae are induced to produce carotene by culturing the algae with high light exposure. Beta-carotene may be produced by algae as a photoprotective response. In some embodiments, the algae are induced to produce carotene by culturing the algae by reducing the dilution rate in the raceway pond. Diluting the algae more slowly reduces the light path, and so increases the relative light exposure of the cells, which can induce beta-carotene production as a photoprotective response. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise at least two induction raceway ponds that are connected in parallel to the final raceway pond of the first series of connected raceway ponds. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise one induction raceway pond that is connected in parallel to the final raceway pond of the first series of connected raceway ponds. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise two induction raceway ponds that are connected in parallel to the final raceway pond of the first series of connected raceway ponds. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise three induction raceway ponds that are connected in parallel to the final raceway pond of the first series of connected raceway ponds. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise at least two series of induction raceway ponds that are connected in parallel to the final raceway pond of the first series of connected raceway ponds. In some embodiments, each of the at least two series of induction raceway ponds comprise at least two induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, each of the at least two series of induction raceway ponds comprise two induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, each of the at least two series of induction raceway ponds comprise three induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise two series of induction raceway ponds that are connected in parallel to the final raceway pond of the first series of connected raceway ponds. In some embodiments, each of the two series of induction raceway ponds comprise at least two induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, each of the two series of induction raceway ponds comprise two induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, each of the two series of induction raceway ponds comprise three induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, the one or more induction raceway ponds in the second algal culture phase comprise three series of induction raceway ponds that are connected in parallel to the final raceway pond of the first series of connected raceway ponds. In some embodiments, each of the three series of induction raceway ponds comprise at least two induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, each of the three series of induction raceway ponds comprise two induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, each of the three series of induction raceway ponds comprise three induction raceway ponds that are connected in parallel to the first induction pond in the series. In some embodiments, each of the series of induction raceway ponds, the algae are cultured in water which is at least 25% shallower upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, each of the series of induction raceway ponds, the algae are cultured in water which is at least 20% shallower upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, each of the series of induction raceway ponds, the algae are cultured in water which is at least 15% shallower upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, each of the series of induction raceway ponds, the algae are cultured in water which is at least 10% shallower upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, each of the series of induction raceway ponds, the algae are cultured in water which is at least 5% shallower upon transfer into the final induction pond(s) than upon transfer into the first induction pond. In some embodiments, the culture water depth is at least 40 cm in the induction raceway pond(s). In some embodiments, the culture water depth Is at least 35 cm in the Induction raceway pond(s). In some embodiments, the culture water depth is at least 30 cm in the induction raceway pond(s). In some embodiments, the culture water depth is at least 25 cm in the induction raceway pond(s). In some embodiments, the culture water depth is at least 20 cm in the induction raceway pond(s). In some embodiments, algae are harvested from one or more induction ponds in the second algal culture phase. In some embodiments, algae are harvested from the final induction ponds of the second algal culture phase. In some embodiments, the algae become beige or orange during the second algal culture phase. In some embodiments, the algal growth rate at the end of the second algal culture phase is less than 1.0 d'1. In some embodiments, the algal growth rate at the end of the second algal culture phase is less than 0.9 d 1. In some embodiments, the algal growth rate at the end of the second algal culture phase is less than 0.8 d 1. In some embodiments, the algal growth rate at the end of the second algal culture phase is less than 0.7 d 1. In some embodiments, the algal growth rate at the end of the second algal culture phase is less than 0.6 d-1. In some embodiments, the algal growth rate at the end of the second algal culture phase is less than 0.5 d-1. In some embodiments, the algal growth rate at the end of the second algal culture phase is less than 0.4 d'1. Algal growth rate can be measured by cell density, dry weight biomass, live cell optical density, live cell fluorescence, solvent extracted pigment fluorescence or optical density, carbon content, turbidity or pond tonality via remote sensing imagery. For example, growth rate (p) may be calculated from the change in biomass from one time point (to) to a later time point (ti): n (d-1) = (to- tl) In some embodiments, the second algal culture phase in performed for at least eight days. In some embodiments, the second algal culture phase in performed for at least seven days. In some embodiments, the second algal culture phase in performed for at least six days. In some embodiments, the second algal culture phase in performed for at least five days. In some embodiments, the second algal culture phase in performed for at least four days. In some embodiments, the algal culture is diluted in each induction raceway pond in the second algal culture phase, and pond volume for each pond in the second algal culture phase is modelled by the following equation: Vt = Vq • 2^ln®' wherein Vx is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond. The volume to dilute the pond can then be calculated as V1-V0. Conversely, if one wishes to target a final pond volume or harvest yield, and knows the growth rate at that pond stage, the equation can be modified where the target volume is divided by the exponent to calculate a starting pond volume. This then sets the post-dilution volume for the upstream pond. This allows one to model an entire production system (in terms of pond stage volume) from either i), a starting volume, modelling the downstream ponds to a target final volume or ii), a final pond volume, modelling the upstream ponds to a target starting inoculum volume from the laboratory. In a preferred embodiment, the mean photosynthetically active radiation (PAR) and UV light in each induction raceway pond does not exceed the light photoinhibition parameter (Ekp) of the algae. In some embodiments, the algae are induced to produce carotene by culturing the algae with high salinity. In some embodiments, the algae are cultured at a salinity of at least 40 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 50 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 60 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 70 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 80 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 90 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 100 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 110 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 120 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 130 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 140 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 150 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 160 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 170 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 180 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 190 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of at least 200 parts per thousand (%o). In some embodiments, the algae are cultured at a salinity of 40-200 parts per thousand (%o). In some embodiments, the algae are induced to produce carotene by culturing the algae at low temperature. In some embodiments, the algae are cultured at a temperature of less than 20 °C. In some embodiments, the algae are cultured at a temperature of less than 15 °C. In some embodiments, the algae are cultured at a temperature of less than 10 °C. In some embodiments, the algae are induced to produce carotene by culturing the algae with high salinity and with high light. In some embodiments, the algae are induced to produce carotene by culturing the algae at low temperature and with high light. Algal flow management and operational parameters Algae may be cultivated in seawater, hypersaline water, desalination brine, brackish water, wastewater or freshwater. The choice of water for the culture medium will depend on the algae being grown. Algae will be grown in water that replicates their natural growth environment. In preferred embodiments, the algae are cultured in natural seawater. The use of this water source presents advantages over hypersaline evaporative brine or other high-salt sources of water. For example, seawater is abundantly available worldwide and not constrained to specific geographies where there are evaporative basins or salt flats available. Once the seawater has circulated through at least one raceway pond 100 (e.g., the series of connected raceway ponds 210), it is cleaned of algae and returned to the warmer ocean surface water, down-current at a distance from the intake to avoid intake of water that has already been used for cultivation of the algae. In one embodiment, algae are first cultivated in at least one stage of covered raceway ponds (210A-21OC). The covered raceway ponds (210A-210C) allow for the control of the algae growth environment. The water used to fill the covered raceway ponds (210A-210C) may be filtered or otherwise treated to remove competing and deleterious organisms before being introduced into the covered raceway ponds. In one embodiment, greenhouses 206 are used to cover the raceway ponds 100 and as a result the algae environment is maintained at a higher than ambient temperature. In this embodiment, the temperature within the covered raceway ponds is between 18 °C and 32 °C, for example between 28 °C and 34 °C. This will substantially inactivate organisms acclimated to temperatures of 14°C - 18°C when they are pumped from depth off-shore. Advantageously, covered raceway ponds are less susceptible to contamination, either by bacteria or viruses, or by potentially competing organisms. The relatively controlled environment of the covered raceway pond promotes the algae transitioning into the exponential growth phase. Passive and / or active ventilation may be used in greenhouse 206 to regulate the temperature. As passive ventilation, greenhouse 206 may have walls that have a mesh netting on the inside and are movable outside which can be shut to retain more heat inside the greenhouse (e.g., in winter) or moved to allow free air moment (e.g., in summer). For the active ventilation, if a certain temperature threshold is exceeded, vents turn on to remove heat from greenhouse 206. As the algal cellular density increases, the algae are successively diluted, preferably by being transferred between stages in the series of covered raceway ponds (to covered raceway ponds of successively larger volume (e.g., from stage 210A to stage 210B, from stage 210B to 210C). This successive dilution maintains a relatively low cell density of algae, for example between 100,000 cells / ml and 2,000,000 cells / ml, for example about 350,000 cells / ml. Each transfer of the algae to seed a covered raceway pond in the next stage of the series (i.e., the successive dilution of the algae) can be timed to match the growth rate of the algae, or cellular resource requirements. In one embodiment, algae reside (i.e., have a residence time) in each stage of covered raceway ponds 210A, 210B, 210C for 2 hours to 10 days, for example 2 hours, 3, hours, 5 hours, 12 hours, 24 hours, 36 hours, 2 days, 3, days or 5 days. In one embodiment, the algae reside in each covered raceway pond 210A, 210B, 210C for two days, before being transferred to a raceway pond of larger volume. In one embodiment, algae remain in a covered raceway pond 210A, 210B, 20C for a length of time sufficient for the algae cellular population to at least double, for example 2 hours, 4 hours, 12 hours, 24 hours, 36 hours or 48 hours. In a specific embodiment, algae remain in a covered raceway pond for 24 hours before being transferred to the next stage in the series. Once the algae enter the exponential growth phase, or when sufficient quantities of algae have been cultivated, the algae are transferred to the first stage of open raceway ponds 210D. In one embodiment, the algae and water are transferred in volumes of 1,000 I to 3,000,000 I, for example 360,000 I to 720,000 I, into the first stage of open raceway ponds 210D. The transfer of a relatively large bolus of algae is intended to seed the open raceway ponds to populate the growth environment with a large excess of several orders of magnitude of the product algae relative to any surviving organisms that were within the source water used in the open raceway pond thereby establishing a robust population. The algae may be diluted (i.e., the dilution rate or dilution volume may be increased) by introducing additional water into the current stage of ponds (210A-210E), increasing the volume of water contained within that stage. Additional water may be added by opening the sluice gate of the inlet pipe 108 of a raceway pond 100. Alternatively, the algae may be diluted by transferring the algae to the next stage of ponds and mixing the algae with water already present in those ponds. Algae in an open raceway pond 210D, 210E are successively diluted by increasing the volume or number of open raceway ponds in each stage of the series (e.g., from stage 210D to 210E). This serial dilution maintains the algae at a low enough cell density to sustain exponential growth. In one embodiment, the algae are successively diluted to maintain a cell density of 50,000 cells / ml to 100,000 cells / ml, for example 200,000 cells / ml to 250,000 cells / ml. This approach is completely different to current methods of cultivating algae in which the algae are grown to artificially high densities often reaching cell densities of over 1 million cells / ml. In one embodiment, algae reside (i.e., have a residence time) in each stage of open raceway ponds 210D, 210E for 2 hours to 5 days, for example 2 hours, 3, hours, 5 hours, 12 hours, 24 hours, 36 hours, 2 days, 3, days or 5 days before being transferred to the next stage of open raceway ponds in the series (e.g., from stage 210D to 210E). In a specific embodiment, algae remain in a stage of open raceway ponds 210D for 48 hours before being transferred to the next stage of raceway ponds 210E in the series. In one embodiment, algae remain in a stage of an open raceway pond 210D, 210E for a length of time sufficient for the algae cellular population to at least double, i.e., for one round of cell division to take place. In a specific embodiment, the algae remain in a stage of an open raceway pond 210D, 21OE for a length of time sufficient for one, two, three, four or five rounds of cell division to take place. This may be, for example, 2 hours, 4 hours 12 hours, 24 hours, 36 hours, 48 hours, or 72 hours. This successive dilution of algae maintains a low cell density which advantageously maintains the exponential growth phase, thereby increasing productivity. Furthermore, the problems associated with high-density algal culture methods such using traditional raceway ponds and PBRs 204 are avoided. With each successive dilution of the algae, water is added to, and / or is already present in, the covered and open raceway ponds in the next stage 210A-210E in the series. Following the transfer of the algae and water from one stage to seed the next stage in the series (e.g., from stage 210Ato 210B, from 210B to 210C, from 210C to 210D, from 210D to 210E), the volume of fluid within each raceway pond 100 is equal to the capacity of the raceway pond 100. In one embodiment, the entire volume of water in a raceway pond 100 is replaced every 2 hours to 8 days, or every 4 hours to 8 days, preferably every 24 to 72 hours. In a preferred embodiment, the volume of water passing through the series of connected covered and open raceway ponds 210 in 24 hours is greater than 20-250% of the entire volume of the series of covered and open connected raceway ponds 210, e.g., greater than 30% of the entire volume of the series of covered and open connected raceway ponds, for example greater than 100% for both seed and growth ponds. This exchange rate of water is much higher than in traditional raceway ponds, where the water replacement rate is usually around 0 - 20% in 24 hours, in order to match the growth rate of the cells and rate of evaporation. This high volume of water exchange has several advantages. In traditional raceway ponds a high cell density of algae is maintained, and any contamination can potentially render the entire raceway pond un-harvestable. However, the series of raceway ponds 210 is inherently resilient, as small degrees of contamination do not matter since all of the contaminants are inevitably washed out of the series of ponds, and none of the product algae is reintroduced into the series of raceway ponds. Harvesting the algae Harvesting the algae is preferably performed by a method that can be applied to large amounts of water with relatively low energy investment and capital expenditure cost. Accordingly, in some embodiments, the algae are harvested by tangential flow filtration. In some such embodiments, the tangential flow filtration is performed using filters comprising hydrophilic simple weave (irradiated) polyester fabric. Alternatively, in some embodiments, the algae are harvested by filtering with a rotary mesh screen. In some such embodiments, the screen comprises a (pore-sized) mesh and a filter comprising hydrophilic (irradiated) polyester fabric. In some embodiments, algae are harvested from one or more raceway ponds in the second algal culture phase. In some embodiments, algae are harvested from the final induction raceway pond in the second algal culture phase. Suitable rotary mesh screens include (simple weave) polyester screens that have a pore size of 10-200 pM, preferably a pore size of 20-120 pM. In some embodiments, these screens have been irradiated. Advantageously, this makes the screen more hydrophilic, which improves the filtration rate. Suitable rotary mesh screens may comprise a surfactant coating, such as SAATIcare Hyphyl™. A further example of a suitable rotary mesh screens is monofilament polyester fabric, such as SUPREX (EXTRIS). In the context of rotary mesh screens, the thinner the fibre strands, the larger the percentage of open area for filtration, which the inventors have found to be advantageous for harvest filtration of algae. Accordingly, in some embodiments, the average fibre strand diameter in a rotary mesh screen less than 50 pM. Accordingly, in some embodiments, the rotary mesh screens have a pore size of 10-200 pM and an average fibre strand diameter of less than 50 pM. Accordingly, in some embodiments, the rotary mesh screens have a pore size of 20-120 pM and an average fibre strand diameter of less than 50 pM. Advantageously, these harvesting methods facilitate the concentration of algal cells without exposure to excess shear or breakage. This facilitates, e.g., the harvest of algal cells that have not formed rigid cysts. Advantageously, these harvesting methods do not require the addition of coagulants or flocculants or other expensive forms of cell concentration such as settling tanks or dissolved air flotation. Advantageously, the algal slurry produced by these harvesting methods may contain the original cultivation water and may not require refrigeration. The cells are still vital in the slurry and the dewatering does not typically damage the cells, ensuring high product quality. In some embodiments, harvesting the algae produces a 500-1000-fold concentrated algal slurry. This slurry is more concentrated than that which can be obtained by conventional dewatering tools such as continuous flow centrifugation or microtubule cross-flow micro-filtration. In some embodiments, the algal slurry is further dewatered in a centrifuge. The centrifuge is preferably a low-shear centrifuge. Advantageously, this ensures that the cells are not lysed or disrupted while the extracellular seawater is removed. In some embodiments, this results in an algal slurry that contains at least 10% dry weight, wet biomass. In some embodiments, this results in an algal slurry that contains 10-15% dry weight, wet biomass. In some embodiments, after the algal slurry has been further dewatered in a (low-shear) centrifuge, the algal slurry is refrigerated and then subjected to a continuous flow centrifuge. Advantageously, this ensures a consistent flow of biomass is available for extraction. In some embodiments, the algal slurry is acidified (e.g., to pH <4, such as pH <3.5) prior to the extraction phase. This is advantageous for microalgae that contain a high level of soluble proteins or soluble starches (like chrysolaminarin) because acidification hydrolyses these large molecules to ensure that they do not bind to the carotenoid extracts. Such microalgae include Skeletonema pseudocostatum, some diazotrophic bacteria, and Chlorella sp.. In preferred embodiments, the extraction phase is performed under an inert gas (e.g., a nitrogen blanket). This prevents oxidation of the extracts. Maintenance of the raceway ponds When algae are cultured in a series of connected raceway ponds, such ponds typically produce sequential batches of algae as opposed to the steady state continuous harvesting of algae that is traditionally utilised in algal culture. This means that batches of algae can be separated according to need. For example, as the algae pass through the series of connected ponds, trace contamination from the air or other sources may occur, particularly in the open raceway ponds 100. However, the series of connected raceway ponds of the present invention is inherently resilient, because small degrees of contamination do not matter as none of the product algae is reintroduced and all of the contaminants are eventually washed out of the system 200. Furthermore, in one embodiment the dilution of the algae through the repeat addition of seawater also dilutes any contaminants present. Raceway ponds in the series are connected to allow algae and water to flow from one raceway pond to another, but each pond can be isolated when required. Individual raceway ponds in parallel can also be isolated when required. This is particularly useful to allow the ponds to be cleaned to remove sediment or biofilms. Therefore, between batches of algae in different raceway ponds, where algae are transferred every 2, 3, 4, 5, 6, 8, 10, 12, 24, 36 hours, 2 days, 3 days, 5 days apart, a maintenance step can be introduced wherein each raceway pond in the series is sequentially pumped dry, cleaned, for example with truck-mounted rotating brushes, and flushed with water. A maintenance step can be performed once a month, and every several maintenance steps an extra day may be introduced to add a day for drying the ponds. Equipment can be cleaned with 0.0001-0.01 % peroxyacetic acid or similar disinfectants such as hypochloric acid before it is seeded with algae from the raceway pond in the preceding stage in the series and topped up with fresh water. In this manner, a running cleaning wave can travel through the entire series of connected covered and open raceway ponds (and the harvesting ponds if desired). This may be scheduled according to the prevalence of oceanic contaminants coming in with the fresh seawater or environmental perturbations such as rainfall or sandstorms. General The term “comprising” encompasses “including” as well as “consisting” e.g., a composition “comprising” X may consist exclusively of X or may include something additional e.g., X + Y. The term “about” in relation to a numerical value x is optional and means, for example, x+10%. The various steps of the methods may be carried out at the same time or at different times, in the same geographical location or in different geographical locations, e.g., countries, and by the same or different people or entities. EXAMPLES Example 1 Dunaliella salina was grown in a connected series of 15 raceway ponds. The first fourteen ponds were kept under optimal growth conditions for D. salina by successive dilution with nutrient-rich seawater in the early mornings and H3PO4 addition in the late afternoons. Overall, the nutrients added were 70-110 micromolar nitrate, 6-8 micromolar phosphate and 1 nanomolar iron (III) salt (e.g. ferric chloride). Under these conditions, D. salina was grown on a three-day doubling cycle, such that cell concentration doubled in three days per unit volume of cultivation water. In these ponds, D. salina was present as ‘green’ (low beta-carotene content) cells. In the fifteenth pond, the algae were subjected to nutrient limitation. In particular, seawater was added to this pond without additional supplementation of nitrogen or phosphorus. This resulted in the cells converting to ‘orange’ (high beta-carotene content) cells. The algae were then harvested using filter mesh screens that have a pore size of 23 microns. These are hydrophilic, polyester woven mesh screens that can be applied to tangential flow filtration or rotary drum screens. The relatively gently concentration process very rapidly creates a 500 - 1,000-fold concentration of the cells in the original cultivation water without the need for refrigeration. The cell concentrate (having 2% - 3% dry weight) was further dewatered in a low-shear centrifuge that ensures that the cells are not lysed or disrupted while the extracellular seawater is removed. This centrifuge produced a paste that is 12% -13% dry weight, wet biomass. This paste was refrigerated, and the biomass was subjected to a continuous flow centrifuge to ensure a consistent flow of biomass was available forextraction. All subsequent steps were performed under a nitrogen blanket to prevent oxidation of the extracts. Extraction of all pigments is performed by suspending approximately 417 g / L of the 12% paste in 100% food grade ethyl acetate, to give a 50 g / L dry weight suspension and agitated for 10 minutes. At this point carotenoids, pigments, some lipids and solvent soluble components have been dissolved in the ethyl acetate. The water phase contains cellular debris and the remainder of the biomass as well as the intracellular salt from Dunaliella salina. The two phases were separated, and the water phase is pumped to solar drying and long-term disposal in landfill. The ethyl acetate was cleaned of all particulate biomass by means of depth filtration and the solvent was evaporated with vacuum assisted evaporation to create an oleoresln. At this point, 1 volume of water is added to a volume of ethyl acetate extract. When the ethyl acetate evaporates, the beta-carotene forms a precipitate in water. This reduces the quantity of oleoresin which adheres to vessel walls to facilitate further processing and to avoid a second resuspension process. The ethyl acetate was condensed, recaptured and recycled. It was passed through a drying column to ensure that it was dry and clean before reuse. The oleoresin was saponified by the addition of a 50% sodium hydroxide solution, to give a final concentration of 1 mole per liter, for 1 hour at 60 °C with agitation. The beta-carotene is not water soluble and forms a slurry that is filtered, and the filter cake is washed with water and subsequently dried to produce the primary product. The watery alkali filtrate contains lutein which was available for further processing by transferring it into an organic non-ester solvent, that was re-evaporated, condensed and recycled to form a second oleoresin rich in lutein. This was similarly dried and collected as a second product. The water phase containing sodium magnesium chlorophyllin was acidified to pH 2-3 by the addition of concentrated hydrochloric acid and is mixed with 10% copper sulfate at 60 °C for 1 hour to precipitate chlorophyllin salts. The precipitate was collected and dissolved in 95% ethanol and the pH is adjusted to 11 by the addition of 1M sodium hydroxide. The sodium copper chlorophyllin was filtered, washed and dried as a third product. The watery filtrate was disposed of as the wet biomass remnants above. Chromatograms for the crude carotenoid extract and the purified carotenoid powder at the end of the process are provided in Figures 4A and 4B, respectively. A chromatogram for a reference carotene product, BASF Betatene®30% OLV, 72% all-trans beta carotene is provided in Figure 4C. Example 2 Below describes an example of the ‘hurry up and wait’ approach, where the pond train is optimised for green (fast growing) algae upstream, and orange (slow growing and stressed) algae downstream. A split pond system having 15 pond stages (Greenhouses 1-6, Clean 1-5, Outdoor 1-5) was tested. There were 22 production ponds in total. Greenhouses 1-6 (G1-G6), Clean 1-5 and Outdoor 1-3 (OD1-3) formed a linear series of 14 ponds. The pond train was subsequently non-linear, such that OD3 is a 1:2 split pond (i.e. x1 OD3 feeds x2 OD4) and each OD4 is a 1:3 split pond (i.e. x1 OD4 feeds x3 OD5). Therefore, the pond system contained two OD4 and six OD5 ponds. Preliminary tests showed a D. salina growth rate of 0.7 d 1 in the greenhouse, increasing to 0.78 d1 in the outdoor ponds (pre-stressing). These growth rates are representative of a green, vegetative state, with chlorophyll a being the primary photosynthetic pigment. Conversely, a stressed, orange D. salina culture, high (> 5%) in p-carotene, has a reduced growth rate of ~ 0.26 d'1. Maintaining a reduced N concentration (but not limited) with ambient PAR results in an intermediatory state, where D. salina is beige in colour, growing at 0.40 d-1. For p-carotene production from D. salina, using high light and nitrogen limitation, 5% p-carotene dry weight concentration is achieved after 4 to 6 days of stressing. D. salina was cultured in this split pond system. In this example, all upstream ponds from Outdoor 3 (OD3) are run and optimised on a linear 1-day cycle based on the system growth rates for green cultures. Outdoor 3 (OD3) is a split pond on a 1:2 ratio, where one OD3 transfers into two OD4’s. Due to this split, OD4 ponds are shallower post-transfer which increases the PAR at the representative depth. In addition to a shallower post-transfer depth, the daily dilution can be delayed into the photic period. This increases the amount of PAR and light exposure combined with nitrogen limitation, exacerbates the degree of cell stressing and rate of p-carotene production. In OD4’s, growth rate is approximately 0.4 d’1. However, the system growth rate for this stage is 0.36 d-1 (the minimum observed growth rate). Due to half the transfer volume going into each OD4 (due to the 1:2 split) and growth rates at this stage, this pond stage is able to run on a 2-day growth cycle before achieving a target 1 m pond depth. In other words, OD3 transfers into both OD4’s everyday (1-day cycle), whilst OD4’s transfer into OD5’s every two days. This pond stage specific increase in daily cycle time ensures that the target OD4 final pond volumes (pre-transfer) are achieved. This ensures OD5 ponds are receiving target transfer volume, and do not void this system’s minimum pond depth limit for mixing (20 cm). Having 1-day cycle ponds transfer into 2-day cycle ponds creates a potential bottleneck in the system. This is factored into the design when optimising OD4 pond sizings. This consists of making OD4’s receive and dilute culture from OD3 on day 1, then receiving an additional transfer from OD3 on day 2 (integrated with the existing volume) before diluting the total volume based on growth rate. At the end of OD4 cultivation, the culture has been stressed for 2 days and is beginning to increase in P-carotene concentration. OD4’s then transfer into the final pond stage (OD5’s) for the remaining period of stressing. At this stage, growth rate decreases yet further to 0.26 d-1. To optimise and achieve maximum pond volumes (i.e. 12,000 m3 per OD5 pond) pre-harvest, this final stage is operated on a 4-day cycle. OD4 ponds are split ponds on a 1:3 ratio (two OD4’s feed six OD5’s). This maintains the aforementioned advantage of intentionally operating shallower ponds (on day 1 and 2) in this final stage, which increases sample depth PAR, which in turn increases the degree of algal stressing and p-carotene production. It also means that OD5 ponds are optimised to receive OD4 transfers on day 1 and day 3. In other words, for every OD5 cycle (4 days), OD4 performs two cycles, and OD3 (and upstream) perform four cycles. The algae are harvested from the OD5 ponds. In this example system, the ‘hurry up and wait’ approach maximised cycle harvested biomass as 1584 kg, which constitutes 396 kg d'1, with cellular p-carotene content of 5%. This yields 19.8 kg p-carotene d-1 and 2.123 kg p-carotene ha d-1. The details for this pond system are provided in Tables 1-5. This approach provided greatly improved land use-normalised yield (kg p-carotene ha d-1) compared to a linear system cultivating green or beige algae. As a comparison, with an equivalent site area to the hurry up and wait design, a linear 1-day pond cycle growing green (fast growth) D. salina at 0.78 d 1 requires 15 pond stages (G1-G5, Clean 1-5, OD1-5) with 60 production ponds in total. The details for this pond system are provided in Tables 6-10. This approach delivers 264 kg d-1 of biomass from 48,000 m3 d'1. p-carotene content in green biomass is significantly lower (0.1 to 0.5%). Even assuming the upper estimate, yields reduce to 1.320 kg p-carotene d-1 and 0.149 kg p-carotene ha d'1; an order of magnitude lower than the hurry up and wait approach. Alternatively, again using an equivalent site area to the hurry up and wait design and cultivating beige-like (moderately stressed) D. salina cultures growing at 0.40 d1 requires 29 pond stages (GIGIS, Clean 1-10, OD1-6) with 58 production ponds in total. The details for this pond system are provided in Tables 11-15. This approach delivers a similar daily harvested biomass (354 kg d-1) from 16,101 m3 d-1 but uses an additional more than twice the ponds than the ‘hurry up and wait’ approach. The p-carotene content in beige-like biomass, although higher than green biomass, is still significantly lower (1.8%) than fully stressed cells, making constant beige cultivation yield 6.376 kg p-carotene d-1 and 0.657 kg p-carotene ha d1. For D. salina cultivation of p-carotene, a ‘hurry up and wait’ approach utilising pond splitting gives a 14 times and 3.2 times increase in land use-normalised yield (kg p-carotene ha d 1) compared to a linear system cultivating green or beige algae, respectively. The dynamic system growth rates are far more productive in terms of throughput and yield than trying to maintain a physiologically semi-stressed culture with a constant growth rate throughout the pond train. A split pond system is especially well-suited to deploying the ‘hurry up and wait’ approach. While this approach can be deployed in an entirely linear system, the stressing period and the transition time from green to orange cells would need to be extended for the system to be more productive. Example 3 On a linear system, where growth rate is maximised and sustained throughout the entire production cycle, split ponds has no increase to harvest yields and actually reduces yield normalised to land use. For example, at a growth rate of 1.1 cT1, harvesting 12,000 m3 per day, a linear pond train yields 384 kg biomass on a 1-day cycle and 192 kg biomass on a 2-day cycle). A split pond approach yields the same metrics but requires 68 ponds in comparison to the 11 needed for a linear system. That said, split ponds on a 1:2 factor (i.e. one pond inoculating two ponds) has significant benefits for carotenoid (e.g. p-carotene) production. The reason being, as illustrated in Figure 10, post-transfer / pre-dilution volumes are reduced by a factor of 2, which increases PAR within the water column. This significantly increases the quantity of PAR at depth, as well as the relative fraction of shortwave and UV light in the spectral quality of light. Measuring and / or modelling the incident PAR on the pond surface enables one to calculate the fraction of light being transmitted into the boundary layer (downwelling PAR) versus reflected back into the atmosphere (Upwelling PAR). Having established the PAR at zero-depth (Eo), one can then apply species-specific light attenuation (kdspAR) factors (which are modelled or measured directly by changes in optical density with increasing pathlength) to calculate the PAR at any depth (Ez). Light attenuation is non-linear with depth, so half the pond depth does not equate to a mean PAR of the water column. To assess light availability with depth on algal productivity, one calculates the “representative depth” or “sample depth”, which is the depth at which PAR is the mean of the water column (see Figure 10). With the assumption that all ponds are well mixed, and all algae are evenly distributed within the water column, in-pond PAR at the sample depth can be compared against a measured and / or modelled time-dependent species light photoinhibition parameter (Ekp). This determines a setpoint for the system design, in terms of determining the degree of shallowing of the final few pond stages (i.e. split pond on a 1:2,1:3 or 1:4 ratio) to maximise algal stressing and carotenoid (e.g. p-carotene) production. Example 4 Dunaliella salina was grown and harvested according to the method set out in Example 1. A 2g sample of the harvested biomass was taken and “wet” extraction of trans-beta carotene and lutein was carried out according to the method set out in Example 1. A further 2g sample of the harvested biomass and “dry” extraction of beta carotene and lutein from 2g of the same initial biomass was also carried out according to the method of Example 1, with the addition of a drying step (70 °C overnight) after the algae were harvested. Samples were analysed by chromatography according to Example 1 to obtain an absorbance per gram value for trans beta-carotene and lutein, which are set out in the table below. Biomass type Biomass (g) Solvent Product Absorbance units (xIO4) per gram Dry 2 EtOAc Trans beta-carotene 6,500,088 Lutein 511,247 Wet 2 EtOAc Trans beta-carotene 9,656,406 Lutein 968,418 As shown above, wet extraction resulted in 1.5x and 1 9x the amount of trans beta-carotene and lutein as that obtained via dry extraction. Indeed, given that 2g of wet biomass would contain a significant amount of water, the improvement relative to 2g of dry biomass is especially strong. Accordingly, omitting a drying step from the extraction process is advantageous in terms of extraction efficiency. REFERENCES Bhumibhamon, 0., Sittiphuprasert, U.( Boontaveeyuwat, N. and Praiboon, J., 2003. The optimum use of salinity, nitrate and pond depth for p-carotene production of Dunafieha salina. Agriculture and Natural Resources, 37(1), pp.84-89. Black, H.S., Boehm, F., Edge, R. and Truscott, T.G., 2020. The benefits and risks of certain dietary carotenoids that exhibit both anti-and pro-oxidative mechanisms—A comprehensive review. Antioxidants, 9(3), p.264. Correa, P.S., Morais Junior, W.G., Martins, A.A., Caetano, N.S. and Mata, T.M., 2020. Microalgae biomolecules: Extraction, separation and purification methods. Processes, 9(1), p.10. Ernst, H., Henrich, K., Keller, A., 2003., Method for producing carotenoids, US20060106257A1 Furukawa, T., Watanaba, M. and Shihira-lshikawa, I. Green and blue-light-mediated chloroplast migration in the centric diatom Pleurosira laevis Protoplasma, 203;214-220 (1998). Ghazi, A., 1999. Extraction of P-carotene from orange peels. Food / Nahrung, 43(4), pp.274-277. Grune, T., Lietz, G., Palou, A., Ross, A.C., Stahi, W.. Tang, G., Thurnham, D., Yin, S.A. and Biesaiski, H.K., 2010. p-Carotene is an important vitamin A source for humans. The Jouma! of nutrition, 740(12), pp.2268S-2285S. Gupta, A.K., Seth, K., Maheshwari, K., Baroliya, P.K., Meena, M., Kumar, A. and Vinayak, V., 2021. Biosynthesis and extraction of high-value carotenoid from algae. Frontiers in Bioscience-Landmark, 26(8), pp.171-190. Johnson, E.J., Qin, J., Krinsky, N.I. and Russell, R.M., 1997. p-Carotene isomers in human serum, breast milk and buccal mucosa cells after continuous oral doses of all-trans and 9-cis p-carotene. The Journal of nutrition, 127(1Q), pp.1993-1999. Kraml, M. and Herrmann, H. Red-blue interaction in Mesotaenium chloroplast movement—blue seems to stabilize the transient memory of the phytochrome signal. Photochem. Photobiol., 53:255-259 (1991) Kusmayadi, A., Suyono E. A., Nagarajan, D., Chang, J.-S. and Yen, H.W., Application of computational fluid dynamics (CFD) on the raceway design for the cultivation of microalgae: a review, 2020, Journal of Industrial Microbiology and Biotechnology, 47(4-5):373-382. Mendes, R.L, Fernandes, H.L., Coelho, J., Reis, E.C., Cabral, J.M., Novais, J.M. and Palavra, A.F., 1995. Supercritical CO2 extraction of carotenoids and other lipids from Chlorella vulgaris. Food chemistry, 53(1), pp.99-103. Takaichi, S. Carotenoids in Algae: Distributions, Biosyntheses and Functions, 2011, Marine Drugs 9(6):1101-1118. Wolf L., Cummings, T., Muller, K., Reppke, M., Volkmar, M. and Weuster-Botz, D., 2021. Production of p-carotene with Dunaiiella salina CCAP19 / 18 at physically simulated outdoor conditions. Engineering in life sciences, 21(3-4), pp.115-125. TABLES Table 1 - Split pond 1-day cycle specification (orange algae) Description Unit Outdoors Outdoor 4 Outdoor 3 Outdoor 2 Outdoor 1 Center Length m 200.30 155.28 114.28 74.93 49.13 Channel Width m 25.04 19.41 14.28 9.37 6.14 Pond Width m 50.08 38.82 28.57 18.73 12.28 Pond Aspect Ratio 8 8 8 8 8 Center Area m2 10031 6028 3265 1404 603 Turn Area m2 1969 1184 641 276 118 Pond Area m2 12000 7212 3906 1679 722 Pond Volume m3 12000 7212 3905.852 1679.129 721.860 Total Pond Area m2 72000 14423 3906 1679 722 Size % 20.0% 27.1% 43.0% 43.0% Depth m 1.0 1.0 1.0 1.0 1.0 SA:V Ratio 1.00 1.00 1.00 1.00 1.00 Overall Pond Length m 250.38 194.10 142.85 93.66 61.41 Overall Pond Width m 50.08 38.82 28.57 18.73 12.28 Number of Ponds in Use 6 2 1 1 1 M d1 0.260 0.360 0.780 0.780 0.780 Bag Volume L 7210.959 3905.490 1678.955 721.776 Transfer Fraction 0.950 0.950 0.950 0.950 0.950 Remaining Fraction 0.050 0.050 0.050 0.050 0.050 Description Unit Clean 5 Clean 4 Clean 3 Clean 2 Clean 1 Center Length m 32.21 21.12 13.85 9.08 5.95 Channel Width m 4.03 2.64 1.73 1.14 0.74 Pond Width m 8.05 5.28 3.46 2.27 1.49 Pond Aspect Ratio 8 8 8 8 8 Center Area m2 259 112 48 20.6 8.9 Turn Area m2 51 22 9 4.0 1.7 Pond Area m2 310 133 57 24.7 10.6 Pond Volume m3 310.327 133.409 57.355 24.659 10.603 Total Pond Area m2 310.3 133.4 57.4 24.7 10.6 Size % 43.0% 43.0% 43.0% 43.0% 43.0% Depth m 1.0 1.0 1.0 1.0 1.0 SA:V Ratio 1.00 1.00 1.00 1.00 1.00 Overall Pond Length m 40.26 26.40 17.31 11.35 7.44 Overall Pond Width m 8.05 5.28 3.46 2.27 1.49 Number of Ponds in Use 1 1 1 1 1 M d1 0.780 0.780 0.780 0.780 0.780 Bag Volume L 310.288 133.391 57.344 24.652 10.597 Transfer Fraction 0.950 0.950 0.950 0.950 0.950 0.950 Remaining Fraction 0.050 0.050 0.050 0.050 0.050 0.050 Description Unit G5 G4 G3 G2 G1 Center Length m 3.90 2.68 1.85 1.56 1.91 Channel Width m 0.49 0.33 0.23 0.20 0.32 Pond Width m 0.98 0.67 0.46 0.39 0.64 Pond Aspect Ratio 8 8 8 8 6 Center Area m2 3.8 1.8 0.9 0.61 1.2 Turn Area m2 0.7 0.4 0.2 0.12 0.3 Pond Area m2 4.6 2.1 1.02 0.73 1.5 Pond Volume m3 4.6 2.1 1.02 0.47 1.5 Total Pond Area m2 4.56 2.14 1.02 0.73 1.54 Size % 43.0% 47.0% 47.8% 71.1% 211.4% Depth m 1.0 1.0 1.0 0.65 1.0 SAV Ratio 1.00 1.00 1.00 1.54 1.00 Overall Pond Length m 4.88 3.35 2.31 1.95 2.55 Overall Pond Width m 0.98 0.67 0.46 0.39 0.64 Number of Ponds in Use 1 1 1 1 1 M d1 0.700 0.700 0.700 0.700 0.700 Bag Volume L 4.556 2.141 1.007 0.472 Transfer Fraction 0.950 0.950 0.950 0.950 0.950 0.950 Remaining Fraction 0.050 0.050 0.050 0.050 0.050 0.050 Description Unit Outdoors Outdoor 4 Outdoor 3 Outdoor 2 Outdoor 1 Day 1 Depth Post Transfer / Pre Dilution m 0.240 0.307 0.458 0.458 0.458 Day 2 Depth Post Transfer / Pre-Dilution m 0.312 0.698 Day 3 Depth - Post Transfer / Pre-Dilution m 0.594 Day 4 Depth Post Transfer / Pre-Dilution m 0.771 Day 1 Depth (Per Pond) Post Transfer / Post Dilution m 0.312 0.440 1.000 1.000 1.000 Day 2 Depth (Per Pond) Post Transfer / Post Dilution m 0.404 1.000 Day 3 Depth (Per Pond) Post Transfer / Post Dilution m 0.771 Day 4 Depth (Per Pond) Post Transfer / Post Dilution m 1.000 Day 1 Volume (Per Pond) Remaining Culture m3 600 361 195 84 36 Day 2 Volume (Per Pond) Remaining Culture m3 3740 3176 Day 3 Volume (Per Pond) Remaining Culture m3 4850 Day 4 Volume (Per Pond) Remaining Culture m3 9252 Day 1 Volume (Per Pond) Transfer Culture m3 2283 1855 1595 686 295 Day 2 Volume (Per Pond) Transfer Culture m3 0 1855 Day 3 Volume (Per Pond) Transfer Culture m3 2283 Day 4 Volume (Per Pond) Transfer Culture m3 0 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 2883 2216 1790 770 331 Day 2 Volume (Per Pond) Post Transfer / Pre Dilution m3 3740 5031 Day 3 Volume (Per Pond) Post Transfer / Pre Dilution m3 7134 Day 4 Volume (Per Pond) Post Transfer / Pre Dilution m3 9252 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 3740 3176 3905 1679 722 Day 2 Volume (Per Pond) Post Transfer / Post Dilution m3 4850 7211 Day 3 Volume (Per Pond) Post Transfer / Post Dilution m3 9252 Day 4 Volume (Per Pond) Post Transfer / Post Dilution m3 11999 Day 1 Volume (All Pond) m3 22438 6352 3905 1679 722 Day 2 Volume (All Pond) m3 29100 14422 Day 3 Volume (All Pond) m3 55510 Day 4 Volume (All Pond) m3 71993 Day 1 Water Demand (All Pond) Seawater for Dilution m3 22438 6352 3905 1679 722 Day 2 Water Demand (All Pond) Seawater for Dilution m3 29100 14422 0 0 0 Day 3 Water Demand (All Pond) Seawater for Dilution m3 55510 0 0 0 0 Day 4 Water Demand (All Pond) Seawater for Dilution m3 71993 0 0 0 0 Description Unit Clean 5 Clean 4 Clean 3 Clean 2 Clean 1 Day 1 Depth Post Transfer / Pre Dilution m 0.458 0.458 0.458 0.458 0.458 Day 1 Depth (Per Pond) Post Transfer / Post Dilution m 1.000 1.000 1.000 1.000 1.000 Day 1 Volume (Per Pond) Remaining Culture m3 15.5 6.7 2.9 1.2 0.5 Day 1 Volume (Per Pond) Transfer Culture m3 126.7 54.5 23.4 10.1 4.3 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 142.2 61.1 26.3 11.3 4.9 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 310 133 57 25 11 Day 1 Volume (All Pond) m3 310.3 133.4 57.3 24.7 10.6 Day 1 Water Demand (All Pond) Seawater for Dilution m3 310 133 57 25 11 Day 2 Water Demand (All Pond) Seawater for Dilution m3 0 0 0 0 0 Day 3 Water Demand (All Pond) Seawater for Dilution m3 0 0 0 0 0 Day 4 Water Demand (All Pond) Seawater for Dilution m3 0 0 0 0 0 Description Unit G5 G4 G3 G2 G1 Day 1 Depth Post Transfer / Pre Dilution m 1.000 1.000 0.983 0.649 Day 1 Depth (Per Pond) Post Transfer / Post Dilution m 0.23 0.11 0.05 0.02 Day 1 Volume (Per Pond) Remaining Culture m3 2.03 0.96 0.45 0.21 Day 1 Volume (Per Pond) Transfer Culture m3 2.26 1.06 0.50 0.23 1.32 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 5 2 1 0 3 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 4.56 2.14 1.01 0.47 2.65 Day 1 Volume (All Pond) m3 5 2 1 0 3 Day 1 Water Demand (All Pond) Seawater for Dilution m3 0 0 0 0 0 Day 2 Water Demand (All Pond) Seawater for Dilution m3 0 0 0 0 0 Day 3 Water Demand (All Pond) Seawater for Dilution m3 0 0 0 0 0 Day 4 Water Demand (All Pond) Seawater for Dilution m3 5 2 1 0 3 Description Unit Value Site Area m2 93276 Site Area ha 9.33 Min Daily Inlet Volume m3 35643 Max Daily Inlet Volume m3 55510 Mean Daily Inlet Volume m3 45577 Dilution Period h 22 Pumping Rate m3 / h 2072 Harvesting Volume m3 71993 Target Biomass Concentration g m3 22 Cycle Biomass Productivity kg 1584 P-carotene % 5 p-carotene kg 79.2 Harvesting Cycle Time d 4 Daily Production kg d 1 19.8 Land-Normalised Daily Production kg ha d-1 2.123 Bag Number 25 Bag Total Volume L 500 Bag Discard Volume L 12.58537 Sustainable Bag Volume to Transfer L 251.7073 Unsustainable Bag Volume to Transfer L 500 Day 1 G1 Restart Depth m 0.6545 Day 1 G1 Restart Volume (Theoretical) m3 1.0069 Day 1 G1 Discard Volume m3 -0.5316 Number of Bag transfers to GO 3 G1 Fill Volume m3 1.5 G2 Inoculation Volume m3 0.222 G1 Post-Transfer Volume m3 1.316 Description Unit Outdoors Outdoor 4 Outdoor 3 Outdoor 2 Outdoor 1 Center Length m 200.30 135.62 91.82 62.17 42.09 Channel Width m 25.04 16.95 11.48 7.77 5.26 Pond Width m 50.08 33.90 22.96 15.54 10.52 Pond Aspect Ratio 8 8 8 8 8 Center Area m2 10031 4598 2108 966 443 Turn Area m2 1969 903 414 190 87 Pond Area m2 12000 5501 2522 1156 530 Pond Volume m3 12000 5501 2522 1156 530 Total Pond Area m2 48000 22004 10087 4624 2120 Size % - 45.8% 45.8% 45.8% 45.8% Number of Ponds on Site 4 4 4 4 4 Depth m 1.0 1.0 1.0 1.0 1.0 SA:V Ratio 1.00 1.00 1.00 1.00 1.00 Overall Pond Length m 250.38 169.52 114.78 77.71 52.61 Overall Pond Width m 50.08 33.90 22.96 15.54 10.52 Number of Ponds in Use 4 4 4 4 4 M d'1 0.780 0.780 0.780 0.780 0.780 Description Unit Clean 5 Clean 4 Clean 3 Clean 2 Clean 1 Center Length m 28.50 19.30 13.06 8.84 6.21 Channel Width m 3.56 2.41 1.63 1.11 0.78 Pond Width m 7.12 4.82 3.27 2.21 1.55 Pond Aspect Ratio 8 8 8 8 8 Center Area m2 203 93 42.7 19.6 9.7 Turn Area m2 40 18 8.4 3.8 1.9 Pond Area m2 243 111 51.0 23.4 11.5 Pond Volume m3 243 111 51.0 23.4 11.5 Total Pond Area m2 972 445 204.2 93.6 46.2 Size % 45.8% 45.8% 45.8% 45.8% 49.4% Number of Ponds on Site 4 4 4 4 4 Depth m 1.0 1.0 1.0 1.0 1.0 SA:V Ratio 1.00 1.00 1.00 1.00 1.00 Overall Pond Length m 35.62 24.12 16.33 11.05 7.77 Overall Pond Width m 7.12 4.82 3.27 2.21 1.55 Number of Ponds in Use 4 4 4 4 4 M d-1 0.780 0.780 0.780 0.706 0.706 Description Unit G5 G4 G3 G2 G1 Center Length m 4.37 3.43 2.67 2.14 1.54 Channel Width m 0.55 0.43 0.33 0.27 0.26 Pond Width m 1.09 0.86 0.67 0.54 0.51 Pond Aspect Ratio 8 8 8 8 6 Center Area m2 4.8 2.94 1.79 1.15 0.79 Turn Area m2 0.9 0.58 0.35 0.23 0.21 Pond Area m2 5.70 3.52 2.14 1.37 1.00 Pond Volume m3 5.70 2.81 1.39 0.69 1.00 Total Pond Area m2 22.81 14.07 8.55 5.49 4.00 Size % 49.4% 61.7% 60.8% 64.2% 46.8% Number of Ponds on Site 4 4 4 4 4 Depth m 1.0 0.80 0.65 0.50 1.00 SA:V Ratio 1.00 1.25 1.54 2.00 1.00 Overall Pond Length m 5.46 4.29 3.34 2.68 2.06 Overall Pond Width m 1.09 0.86 0.67 0.54 0.51 Number of Ponds in Use 4 4 4 4 4 M d-1 0.706 0.706 0.706 0.706 0.706 Description Units Outdoors Outdoor 4 Outdoor 3 Outdoor 2 Outdoor 1 Day 1 Depth Post Transfer / Pre Dilution m3 0.458 0.458 0.458 0.458 0.458 Day 1 Depth Post Transfer / Post Dilution m3 0.250 0.250 0.250 0.250 0.250 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 5501 2522 1156 530 243 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 12000 5501 2522 1156 530 Day 1 Volume (All Pond) m3 48001 22004 10087 4624 2120 Day 1 Water Demand (All Pond) m3 25997 11917 5463 2504 1148 Table 8 - Linear pond cycle outline for “clean” ponds (green algae) Description Units Clean 5 Clean 4 Clean 3 Clean 2 Clean 1 Day 1 Depth Post Transfer / Pre Dilution m3 0.458 0.458 0.458 0.494 0.494 Day 1 Depth Post Transfer / Post Dilution m3 0.250 0.250 0.250 0.250 0.250 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 111 51 23 11.55 5.70 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 242.9 111.4 51.0 23.4 11.6 Day 1 Volume (All Pond) m3 972 445 204 94 46 Day 1 Water Demand (All Pond) m3 526 241 111 47 23 10 Description Units G5 G4 G3 G2 G1 Day 1 Depth Post Transfer / Pre Dilution m3 0.494 0.395 0.321 0.247 Day 1 Depth Post Transfer / Post Dilution m3 0.250 0.250 0.250 0.250 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 2.82 1.39 0.69 0.34 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 5.703 2.815 1.390 0.686 0.25 Day 1 Volume (All Pond) m3 22.81 11.26 5.56 2.74 1.00 Day 1 Water Demand (All Pond) m3 11.55 5.70 5.22 2.41 0.34 Description Unit Value Site Area m2 88650 Site Area ha 8.87 Daily Inlet Volume m3 48004 Dilution Period h 22 Pumping Rate m3 / h 2182 Daily Harvesting Volume m3 12000 Target Biomass Concentration g m3 22 Cycle Biomass Productivity kg 264 p-carotene % 0.5 p-carotene kg 1.320 Harvesting Cycle Time d 1 Daily Production kg d ‘1 1.320 Land-Normalised Daily Production kg ha d 1 0.149 Bag Volume L 25 Bag Number 20 Bag Total Volume L 500 Bag Discard Volume L 12.66 Sustainable Bag Volume to Transfer L 253.2 Unsustainable Bag Volume to Transfer L 500 Day 1 G1 Restart Depth m 1.013 Day 1 G1 Restart Volume m3 1.013 Day 1 G1 Discard Volume L 0.506 G1 Fill Volume m3 1.000 G2 Inoculation Volume m3 0.34 G1 Remaining Volume m3 0.661 G1 Discard Volume m3 0.168 Description Unit Oudoor 6 Outdoor 5 Outdoor 4 Outdoor 3 Outdoor 2 Outdoor 1 Center Length m 232.02 189.65 155.00 126.70 103.55 84.64 Channel Width m 29.00 23.71 19.38 15.84 12.94 10.58 Pond Width m 58.01 47.41 38.75 31.67 25.89 21.16 Pond Aspect Ratio 8 8 8 8 8 8 Center Area m2 13458 8992 6007 4013 2681 1791 Turn Area m2 2643 1765 1179 788 526 352 Pond Area m2 16101 10757 7186 4801 3207 2143 Pond Volume m3 16101 10757 7186 4801 3207 2143 Total Pond Area m2 32202 21514 14372 9602 6414 4286 Size % 66.8% 66.8% 66.8% 66.8% 66.8% Number of Ponds on Site 2 2 2 2 2 2 Depth m 1.0 1.0 1.0 1.0 1.0 1.0 SA:V Ratio 1.00 1.00 1.00 1.00 1.00 1.00 Overall Pond Length m 290.03 237.06 193.76 158.37 129.44 105.80 Overall Pond Width m 58.01 47.41 38.75 31.67 25.89 21.16 Number of Ponds in Use 2 2 2 2 2 2 M d'1 0.40 0.40 0.40 0.40 0.40 0.40 Description Unit Clean 10 Clean 9 Clean 8 Clean 7 Clean 6 Clean 5 Center Length m 69.18 56.55 46.22 37.78 30.88 25.24 Channel Width m 8.65 7.07 5.78 4.72 3.86 3.15 Pond Width m 17.30 14.14 11.55 9.44 7.72 6.31 Pond Aspect Ratio 8 8 8 8 8 8 Center Area m2 1197 799 534 357 238 159 Turn Area m2 235 157 105 70 47 31 Pond Area m2 1431 956 639 427 285 191 Pond Volume m3 1431 956 639 427 285 191 Total Pond Area m2 2863 1913 1278 854 570 381 Size % 66.8% 66.8% 66.8% 66.8% 66.8% 66.8% Number of Ponds on Site 2 2 2 2 2 2 Depth m 1.0 1.0 1.0 1.0 1.0 1.0 SA:V Ratio 1.00 1.00 1.00 1.00 1.00 1.00 Overall Pond Length m 86.48 70.69 57.77 47.22 38.60 31.55 Overall Pond Width m 17.30 14.14 11.55 9.44 7.72 6.31 Number of Ponds in Use 2 2 2 2 2 2 M d1 0.40 0.40 0.40 0.40 0.40 0.40 Description Unit Clean 4 Clean 3 Clean 2 Clean 1 G13 G12 Center Length m 20.63 16.86 13.78 11.26 9.20 7.52 Channel Width m 2.58 2.11 1.72 1.41 1.15 0.94 Pond Width m 5.16 4.21 3.45 2.82 2.30 1.88 Pond Aspect Ratio 8 8 8 8 8 8 Center Area m2 106 71 47 32 21 14 Turn Area m2 21 14 9 6 4 3 Pond Area m2 127 85 57 38 25 17 Pond Volume m3 127 85 57 38 25 17 Total Pond Area m2 255 170 114 76 51 34 Size % 66.8% 66.8% 66.8% 66.8% 66.8% 66.8% Number of Ponds on Site 2 2 2 2 2 2 Depth m 1.0 1.0 1.0 1.0 1.0 1.0 SA:V Ratio 1.00 1.00 1.00 1.00 1.00 1.00 Overall Pond Length m 25.79 21.07 17.23 14.08 11.51 9.41 Overall Pond Width m 5.16 4.21 3.45 2.82 2.30 1.88 Number of Ponds in Use 2 2 2 2 2 2 M d1 0.40 0.40 0.40 0.40 0.40 0.40 Description Unit G11 G10 G9 G8 G7 G6 Center Length m 6.15 5.03 4.11 3.36 2.74 2.25 Channel Width m 0.77 0.63 0.51 0.42 0.34 0.28 Pond Width m 1.54 1.26 1.03 0.84 0.69 0.56 Pond Aspect Ratio 8 8 8 8 8 8 Center Area m2 9 6 4 2.8 1.9 1.3 Turn Area m2 2 1 1 0.6 0.4 0.2 Pond Area m2 11 8 5 3.4 2.2 1.5 Pond Volume m3 11 8 5 3.4 2.2 1.5 Total Pond Area m2 23 15 10 6.7 4.5 3.0 Size % 66.8% 66.8% 66.8% 66.7% 66.8% 67.1% Number of Ponds on Site 2 2 2 2 2 2 Depth m 1.0 1.0 1.0 1.0 1.0 1.0 SA:V Ratio 1.00 1.00 1.00 1.00 1.00 1.00 Overall Pond Length m 7.69 6.28 5.14 4.20 3.43 2.81 Overall Pond Width m 1.54 1.26 1.03 0.84 0.69 0.56 Number of Ponds in Use 2 2 2 2 2 2 M d1 0.40 0.40 0.40 0.40 0.40 0.40 Description Unit G5 G4 G3 G2 G1 Center Length m 1.84 1.67 1.52 1.42 1.54 Channel Width m 0.23 0.21 0.19 0.18 0.26 Pond Width m 0.46 0.42 0.38 0.35 0.51 Pond Aspect Ratio 8 8 8 8 6 Center Area m2 0.8 0.70 0.58 0.50 0.79 Turn Area m2 0.2 0.14 0.11 0.10 0.21 Pond Area m2 1.01 0.84 0.69 0.60 1.00 Pond Volume m3 1.01 0.67 0.45 0.30 1.00 Total Pond Area m2 2.02 1.67 1.38 1.20 2.00 Size % 66.9% 82.9% 82.7% 86.7% 144.4% Number of Ponds on Site 2 2 2 2 2 Depth m 1.0 0.80 0.65 0.50 1.00 SA:V Ratio 1.00 1.25 1.54 2.00 1.00 Overall Pond Length m 2.30 2.09 1.90 1.77 2.06 Overall Pond Width m 0.46 0.42 0.38 0.35 0.51 Number of Ponds in Use 2 2 2 2 2 M d1 0.40 0.40 0.40 0.40 0.40 Description Units Outdoor 6 Outdoor 5 Outdoor 4 Outdoor 3 Outdoor 2 Outdoor 1 Day 1 Depth Post Transfer / Pre Dilution m3 0.668 0.668 0.668 0.668 0.668 0.668 Day 1 Depth Post Transfer / Post Dilution m3 0.500 0.500 0.500 0.500 0.500 0.500 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 10757 7186 4801 3207 2143 1432 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 16101 10757 7186 4801 3207 2142.8 Day 1 Volume (All Pond) m3 32202 21513 14372 9602 6415 4286 Day 1 Water Demand (All Pond) m3 10689 7141 4771 3187 2129 1422 Description Units Clean 10 Clean 9 Clean 8 Clean 7 Clean 6 Day 1 Depth Post Transfer / Pre Dilution m3 0.668 0.668 0.668 0.668 0.668 Day 1 Depth Post Transfer / Post Dilution m3 0.500 0.500 0.500 0.500 0.500 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 956 639 427 285 191 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 1431.5 956.4 638.9 426.8 285.2 Day 1 Volume (All Pond) m3 2863 1913 1278 854 570 Day 1 Water Demand (All Pond) m3 950 635 424 283 189 Description Units Clean 5 Clean 4 Clean 3 Clean 2 Clean 1 Day 1 Depth Post Transfer / Pre Dilution m3 0.668 0.668 0.668 0.668 0.668 Day 1 Depth Post Transfer / Post Dilution m3 0.500 0.500 0.500 0.500 0.500 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 127 85 57 38 25 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 190.5 127.3 85.0 56.81 37.95 Day 1 Volume (All Pond) m3 381 255 170 114 76 Day 1 Water Demand (All Pond) m3 126 84 56 38 25 Description Units G13 G12 Day 1 Depth Post Transfer / Pre Dilution m3 0.668 0.668 Day 1 Depth Post Transfer / Post Dilution m3 0.500 0.500 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 17 11 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 25.35 16.94 Day 1 Volume (All Pond) m3 51 34 Day 1 Water Demand (All Pond) m3 17 11 Description Units G8 G7 Day 1 Depth Post Transfer / Pre Dilution m3 0.669 0.669 Day 1 Depth Post Transfer / Post Dilution m3 0.501 0.501 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 2 1.51 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 3.37 2.25 Day 1 Volume (All Pond) m3 7 5 Day 1 Water Demand (All Pond) m3 2 1 Description Units G3 G2 Day 1 Depth Post Transfer / Pre Dilution m3 0.433 0.334 Day 1 Depth Post Transfer / Post Dilution m3 0.499 0.500 Day 1 Volume (Per Pond) Post Transfer / Pre Dilution m3 0.30 0.20 Day 1 Volume (Per Pond) Post Transfer / Post Dilution m3 0.45 0.30 G11 G10 G9 0.668 0.668 0.668 0.500 0.500 0.500 8 5 3 11.32 7.56 5.05 23 15 10 8 5 3 G6 G5 G4 0.666 0.666 0.536 0.499 0.498 0.502 1.01 0.67 0.45 1.51 1.01 0.67 3 2.01 1.34 1 0.67 0.45 G1 0.50 Day 1 Volume (All Pond) m3 0.90 0.60 1.00 Day 1 Water Demand (All Pond) m3 0.70 0.40 0.20 Description Unit Value Site Area m2 97017 Site Area ha 9.70 Daily Inlet Volume m3 32202 Dilution Period h 22 Pumping Rate m3 / h 1464 Daily Harvesting Volume m3 16101 Target Biomass Concentration g m3 22 Cycle Productivity kg 354 p-carotene % 1.8 p-carotene kg 6.376 Harvesting Cycle Time d 1 Daily Production kg d ‘1 6.376 Land-Normalised Daily Production kg ha d 1 0.657 Bag Volume L 25 Bag Number 20 Bag Total Volume L 500 Bag Discard Volume L 8.30 Sustainable Bag Volume to Transfer L 166.0 Unsustainable Bag Volume to Transfer L 500 Day 1 G1 Restart Depth m 0.748 Day 1 G1 Restart Volume m3 0.748 Day 1 G1 Discard Volume L 0.332 G1 Fill Volume m3 1.000 G2 Inoculation Volume m3 0.20 G1 Remaining Volume m3 0.800 G1 Discard Volume m3 0.132

Claims

1. A method for producing a carotenoid, wherein the method comprises:(a) a first algal culture phase,wherein the first algal culture phase comprises culturing marine carotenoid-producing microalgae in a first series of connected raceway ponds, arranged in stages,and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition;(b) a second algal culture phase,wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a),wherein the algae are cultured:(i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and(ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen),thereby inducing the algae to increase carotenoid production;(c) a harvest phase,wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and(d) an extraction phase,wherein the extraction phase comprises extracting the carotenoid from the algae harvested in step (c).

2. The method of claim 1, wherein, upon transfer into each of the one or more induction raceway ponds, the algae are cultured in water that is at least 10% shallower than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds.

3. The method of claim 1 or claim 2, wherein the algae are cultured in shallower water, for at least the first day following transfer into each of the one or more induction raceway ponds, than the water in which the algae are cultured in the final raceway pond of the first series of connected raceway ponds.

4. The method of any one of claims 1-3, wherein the mean UV and photosynthetically active radiation (PAR) does not exceed the light photoinhibition parameter (Ekp) of the algae.

5. The method of any one of claims 1-4, wherein the culture water depth is at least 20 cm in the induction raceway pond(s).

6. The method of any one of claims 1 -5, wherein the one or more induction raceway ponds in step (b) comprise at least two induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds.

7. The method of claim 6, wherein the one or more induction raceway ponds in step (b) comprise at least two series of induction raceway ponds that are connected, in parallel, to the final raceway pond of the first series of connected raceway ponds.

8. The method of claim 7, wherein each of the at least two series of induction raceway ponds comprises:(i) at least two induction raceway ponds that are connected, in parallel, to the first induction pond in the series, or(ii) at least three induction raceway ponds that are connected, in parallel, to the first induction pond in the series.

9. The method of claim 7 or claim 8, wherein in each of the series of induction raceway ponds, the algae are cultured in (10%) shallower water upon transfer into the final induction pond(s) than upon transfer into the first induction pond.

10. The method of any one of claims 7-9, wherein the harvesting algae in step (c) is from the final induction ponds.

11. The method of any one of claims 1-10, wherein the algae are green during the first algal culture phase, and wherein the algae become beige or orange during the second algal culture phase.

12. The method of any one of claims 1-11, wherein the marine carotenoid-producing microalgae are Chlorophyta, Chlorarachniophyta, Haptophyta, Dinophyta, Euglenophyta, Heterokontophyta (e.g. Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, Xanthophyceae or Eustigmatophyceae), Cryptophyta, unicellular Rhodophyta, Glaucophyta or Cyanophyta,optionally wherein the marine carotenoid-producing microalgae are:(a) Rhopalodiaceae sp., Hemiaulus sp., Climacodium sp., Skeletonema sp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp., or(b) Dunaliella sp.

13. The method of claim 12, wherein the marine carotenoid-producing microalgae are Chlorophyta (e.g. Dunaliella sp.) or Chlorarachniophyta.

14. The method of claim 13, wherein the marine carotenoid-producing microalgae are Dunaliella sp. (e.g. D. salina).

15. The method of any one of claims 1-14, wherein the carotenoid is beta-carotene.

16. The method of any one of claims 1-14, wherein the carotenoid is a xanthophyll.

17. The method of claim 16, wherein the xanthophyll is lutein.

18. The method of claim 16, wherein the xanthophyll is:(A) diadinoxanthin,optionally wherein the marine carotenoid-producing microalgae are Heterokontophyta (e.g. Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, orXanthophyceae), Haptophyta, Dinophyta or Euglenophyta,(B) zeaxanthin,optionally wherein the marine carotenoid-producing microalgae are Chlorophyta, Chlorarachniophyta, Haptophyta, Dinophyta, Euglenophyta, Heterokontophyta (e.g., Chrysophyceae, Raphidophyceae, Bacillariophyceae, Phaeophyceae, orXanthophyceae), Cryptophyta, unicellular Rhodophyta, Glaucophyta or Cyanophyta,optionally further wherein the marine carotenoid-producing microalgae are:(i) Rhopalodiaceae sp., Hemiaulus sp., Climacodiurn sp., Skeletonema spp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp., or Nitzschia sp., or(ii) Dunaliella sp., or(iii) Trichodesmium sp., Richelia sp., Calothrixsp., Crocosphaera sp., or Candidatus Atelocyanobacterium Thalassa,(C) violaxanthin,optionally wherein the marine carotenoid-producing microalgae are Chlorophyta(e.g. Dunaliella sp.), Chlorarachniophyta, or Heterokontophyta (e.g. Raphidophyceae, Phaeophyceae, or Eustigmatophyceae),(D) neoxanthin,optionally wherein the marine carotenoid-producing microalgae are Euglenophyta, Chlorophyta (e.g. Dunaliella sp.) or Chlorarachniophyta,(E) fucoxanthin,optionally wherein the marine carotenoid-producing microalgae are Heterokontophyta(e.g. Chrysophyceae, Raphidophyceae, Bacillariophyceae, or Phaeophyceae), Haptophyta, or Dinophyta,optionally further wherein the marine carotenoid-producing microalgae are Rhopalodiaceae sp. Hemiaulus sp., Climacodium sp., Skeletonema spp., Chaetoceros sp., Thalassiosira sp., Coscinodiscus sp., Navicula sp., Synedra sp. or Nitzschia sp.,(F) vaucheriaxanthin,optionally wherein the marine carotenoid-producing microalgae are Heterokontophyta(e.g. Chrysophyceae or Eustigmatophyceae),(G) loroxanthin,optionally wherein the marine carotenoid-producing microalgae are Euglenophyta, Chlorophyta (e.g. Prasinophyceae, Chlorophyceae or Ulvophyceae) or Chlorarachniophyta,(H) siphonaxanthin,optionally wherein the marine carotenoid-producing microalgae are Euglenophyta or Chlorophyta (e.g., Prasinophyceae, Chlorophyceae or Ulvophyceae),(I) one or more of nostoxanthin, echinenone, myxol glycosides and oscillol glycosides,optionally wherein the marine carotenoid-producing microalgae are Cyanophyta,optionally further wherein the marine carotenoid-producing microalgae are Trichodesmium sp., Richelia sp., Calothrix sp., Crocosphaera sp. or Candidatus Atelocyanobacterium Thalassa,(J) one or more of alloxanthin, crocoxanthin and monadoxanthin, optionally wherein the marine carotenoid-producing microalgae are Cryptophyta,(K) violaxanthin fatty acid ester, optionally wherein the marine carotenoid-producing microalgae are Heterokontophyta(e.g., Xanthophyceae),(L) fucoxanthin fatty acid ester,optionally wherein the marine carotenoid-producing microalgae are Haptophyta,(M) peridinin,optionally wherein the marine carotenoid-producing microalgae are Dinophyta,(N) prasinoxanthin,optionally wherein the marine carotenoid-producing microalgae are Chlorophyta(e.g., Prasinophyceae),(O) loroxanthin fatty acid ester, optionally wherein the marine carotenoid-producing microalgae are Chlorophyta(e.g,. Prasinophyceae) or Chlorarachniophyta, or(P) siphonaxanthin fatty acid ester, optionally wherein the marine carotenoid-producing microalgae are Chlorophyta(e.g. Prasinophyceae, Chlorophyceae or Ulvophyceae).

19. The method of any one of claims 1-18, wherein the algal culture is diluted in each raceway pond in the first algal culture phase, and wherein pond volume for each pond in the first algal culture phase is modelled by the following equation: / H AV^ — Vg ■wherein Vx is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond.

20. The method of any one of claims 1-19, wherein the algal culture is diluted in each induction raceway pond in the second algal culture phase, and wherein pond volume for each pond in the second algal culture phase is modelled by the following equation:Vj = Vo ■ 2®wherein Vx is the final post-dilution pond volume, Vo is the pond volume of the preceding pond, and p is the growth rate of the algae in the preceding pond.

21. The method of any one of claims 1-20, wherein the algal growth rate during step (a) is at least 0.7d-1 (e.g. 0.7-1.0 d-1) and / or wherein the algal growth rate at the end of step (b) is less than 0.6 d-1 (e.g. 0.5 d1).

22. The method of any one of claims 1-21, wherein the series of connected raceway ponds in step (a) is a linear series.

23. The method of any one of claims 1-22, wherein the series of connected raceway ponds in step (a) comprises a first stage comprising one or more covered raceway ponds and a second stage comprising one or more open raceway ponds.

24. The method of any one of claims 1-23, wherein the nutrient addition in step (a) comprises adding one or more nutrient mineral acids, optionally wherein the one or more nutrient mineral acids are selected from nitric acid, phosphoric acid and silicic acid.

25. The method of any one of claims 1-24, wherein the concentration of nitrogen in step (b) is less than 10 pM.

26. The method of any one of claims 1-25, wherein the second algal culture phase is performed for at least four days (e.g. 4-10 days).

27. A method for producing lutein, wherein the method comprises:(a) a first algal culture phase,wherein the first algal culture phase comprises culturing marine lutein-producing microalgae In a first series of connected raceway ponds, arranged in stages,and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition;(b) a second algal culture phase,wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a),wherein the algae are cultured:(i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and(ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen),thereby inducing the algae to increase lutein production;(c) a harvest phase, wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and(d) an extraction phase,wherein the extraction phase comprises extracting the lutein from the algae harvested in step (c).

28. A method for producing zeaxanthin, wherein the method comprises:(a) a first algal culture phase,wherein the first algal culture phase comprises culturing marine zeaxanthin-producing microalgae in a first series of connected raceway ponds, arranged in stages,and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition;(b) a second algal culture phase,wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a),wherein the algae are cultured:(i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and(ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen),thereby inducing the algae to increase zeaxanthin production;(c) a harvest phase,wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and(d) an extraction phase,wherein the extraction phase comprises extracting the zeaxanthin from the algae harvested in step (c).

29. A method for producing a violaxanthin, wherein the method comprises:(a) a first algal culture phase,wherein the first algal culture phase comprises culturing marine violaxanthin-producing microalgae in a first series of connected raceway ponds, arranged in stages, and wherein the algae are maintained in the exponential growth phase by successive dilution with seawater and nutrient addition;(b) a second algal culture phase,wherein the second algal culture phase comprises culturing the algae in one or more induction raceway ponds that are connected to the first series of connected raceway ponds in which algae are cultured in step (a),wherein the algae are cultured:(i) in shallower water upon transfer into each of the one or more induction raceway ponds than in the final raceway pond of the first series of connected raceway ponds, and(ii) in the presence of a low concentration of nitrogen (e.g. less than 10 pM nitrogen),thereby inducing the algae to increase violaxanthin production;(c) a harvest phase,wherein the harvest phase comprises harvesting algae from one or more of the induction raceway pond(s) in which algae are cultured in step (b); and(d) an extraction phase,wherein the extraction phase comprises extracting the violaxanthin from the algae harvested in step (c).102

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