A kind of cultivation nutrient solution suitable for directional improvement of maximum water holding capacity of cyanobacterial crust on calcareous sand of coral island

Abstract

The application discloses a kind of cultivation nutrient solution suitable for directional improvement of maximum water-holding capacity of calcareous sand cyanobacterial crust of coral island.The cultivation nutrient solution contains: glucose 25g / L, sodium dihydrogen phosphate 0.025g / L, potassium chloride 0.1g / L, magnesium chloride 0.05g / L, sodium nitrate 0.1g / L, ferrous chloride 0.005g / L, and the balance is water.The application is based on in-situ collection of cyanobacterial crust, and uses artificial preparation of cultivation nutrient solution to directionally improve hydrological characteristics of cyanobacterial crust from calcareous sand of coral island, which can promote the development of cyanobacterial crust, improve the maximum water-holding capacity of crust, save the use amount of inoculation material, reduce the influence on environment, thereby improve the storage capacity of freshwater of coral island, lay a good material foundation for the change of coral island ecological environment system, and therefore have wide application value.

Description

Technical Field

[0001] This invention belongs to the field of artificial cultivation technology of cyanobacterial crusts and is applicable to calcareous sand substrates. Specifically, it relates to a cultivation nutrient solution suitable for improving the maximum water holding capacity of cyanobacterial crusts in calcareous sands of coral islands. Background Technology

[0002] Biological soil crust (BSC) is a complex formed by algae, lichens, mosses, and other cryptogams and soil microorganisms cementing together with topsoil particles through secretions, rhizoids, and hyphae. It is the most important surface cover in deserts and polar regions, with a coverage rate reaching 60%–70% in the Loess Plateau. Biological crust profoundly influences the material cycle and energy exchange processes of topsoil, significantly improving its physical, chemical, and biological properties. It also possesses multiple ecological functions, including windbreak and sand fixation, water and heat regulation, carbon and nitrogen fixation, increased soil enzyme activity, and enhanced biodiversity, playing a crucial role in soil and vegetation restoration in fragile ecological zones. Biological crust exhibits strong resilience, adapting to extreme drought and infertile environments, thus becoming a pioneer group driving soil formation and primary succession.

[0003] Biocrusts are the most important surface cover on tropical coral islands, with the dominant genus *Chroococcidiopsis*, belonging to the phylum Cyanobacteria. Previous studies have shown that biocrusts on tropical coral islands are in the early stages of succession, also known as cyanobacterial crusts. Tropical coral islands are primarily composed of calcareous coral sand, with a carbonate content as high as 95%, and possess unique environmental characteristics, including a lack of true soil and freshwater resources, high salinity and alkalinity, high temperatures, and intense and prolonged ultraviolet radiation. Almost no plant species can grow and establish themselves on tropical coral islands. However, the presence of biocrusts can effectively enhance soil and water resistance to erosion, reduce soil loss, and provide favorable biological conditions for improving the island's matrix to create a suitable environment for plant growth, especially for freshwater accumulation. Studies have shown that biocrusts can increase rainfall interception, promote condensation capture, enhance surface soil water retention capacity, reduce water infiltration into deeper layers, improve the growth environment for herbaceous plants, and promote rapid succession of artificial vegetation communities. Currently, biocrusts are widely used in ecological restoration projects in desert areas, but their research and application in terrestrial environments of coral islands with calcareous sand as the substrate are still in their early stages. Due to their excellent freshwater storage capacity and ability to promote natural vegetation succession, cultivation methods based on increasing the maximum water holding capacity of biocrusts show promising application prospects. Summary of the Invention

[0004] In view of the lack of existing cultivation nutrient solutions specifically designed to enhance the maximum water holding capacity of cyanobacterial crusts in tropical coral island environments, this invention addresses the characteristics of high and concentrated rainfall in China's tropical coral islands. Based on the principle that protozoan groups can maximize adaptability, this invention utilizes in-situ biological crusts as the cultivation object, artificially prepares cultivation nutrient solutions, promotes the development of cyanobacterial crusts on calcareous coral sand, and enhances their maximum water holding capacity.

[0005] The purpose of this invention is to provide a nutrient solution suitable for directionally increasing the maximum water holding capacity of cyanobacterial crusts on coral islands. This method utilizes cyanobacterial crusts derived from tropical coral islands, inoculated onto calcareous coral sand in a simulated natural coral island environment, and then adds the nutrient solution to achieve a method for obtaining artificially cultivated cyanobacterial crusts with high water holding capacity in indoor cultivation with minimal inoculation.

[0006] The culture nutrient solution contains glucose, sodium dihydrogen phosphate, potassium chloride, magnesium chloride, sodium nitrate, ferrous chloride, and water.

[0007] Preferably, the culture nutrient solution contains: 25 g / L glucose, 0.025 g / L sodium dihydrogen phosphate, 0.1 g / L potassium chloride, 0.05 g / L magnesium chloride, 0.1 g / L sodium nitrate, 0.005 g / L ferrous chloride, and the remainder is water.

[0008] A second objective of this invention is to provide the application of the above-described culture nutrient solution in the rapid cultivation of cyanobacterial crusts and / or in increasing their maximum water holding capacity.

[0009] This invention relates to a cultivation process for increasing the maximum water holding capacity of cyanobacterial crusts grown on a calcareous sand substrate, comprising the following steps:

[0010] a. The raw material is coral island blue bacteria crust growing on a calcareous sand substrate. After being naturally air-dried, it is ground to make seed soil similar to the protozoan crust biological community.

[0011] b. Sow the seed soil evenly on the calcareous sand and cultivate it. After the cultivation begins, spray with artificially prepared nutrient solution at least once, and water regularly at other times to maintain the moisture content of the calcareous sand at 10% to 15%.

[0012] Preferably, in step a, the collected coral island cyanobacterial crusts are air-dried at room temperature (25°C) and then ground to make inoculation material (seed soil).

[0013] Preferably, the inoculation amount of the inoculation material in step b is 240 g / m³. 2 The dosage is far lower than that used in earlier studies, minimizing damage to the in-situ biological crust.

[0014] Preferably, in step b, the moisture content of the calcareous sand is maintained at 14%.

[0015] Preferably, in step b, after the inoculation material is fixed by spraying, the artificially prepared nutrient solution is sprayed only once.

[0016] The nutrient solution for cultivating cyanobacterial crusts provided by this invention utilizes in-situ cyanobacterial crusts collected from tropical coral islands, which are then air-dried and ground to prepare inoculation material. Nutrients and trace mineral elements that promote cyanobacterial growth are selected as the culture medium, and the unit inoculation amount is also taken into account as an influencing factor. The aim is to minimize damage to the in-situ environment through artificial directional cultivation of cyanobacterial crusts, thereby achieving a cultivation effect with maximum water holding capacity.

[0017] This invention was carried out in an artificial climate cultivation chamber. Based on long-term monitoring results of tropical coral islands, the temperature, relative humidity, photoperiod, and light intensity in the artificial climate chamber were set as follows (day / night): 33 / 28.5℃, 68% / 80%, 14 / 10h, and 13000 / 0 lux, respectively. Simultaneously, the cultivation boxes were regularly sprayed with water daily to ensure that the moisture content of the calcareous sand in the cultivation boxes was maintained at 14%.

[0018] Before inoculation, the calcareous sand in the culture box was first treated with water mist to keep it moist. Then, the ground coral island-derived cyanobacterial crust seed soil was evenly spread on the calcareous sand, followed by moistening the calcareous sand again. The inoculation amount of the material was 240 g / m³. 2 Six hours later, the prepared artificial nutrient solution is sprayed evenly onto the surface of the inoculated material in one go. The artificial nutrient solution contains: glucose, sodium dihydrogen phosphate, potassium chloride, magnesium chloride, sodium nitrate, ferrous chloride and water.

[0019] After 120 days of indoor cultivation, obvious cyanobacterial crusts were formed on the calcium sand in the culture boxes. Figure 1 The maximum water holding capacity of all cyanobacterial inoculated crusts (with added artificial nutrient solution) was significantly higher than that of the blank control group (with a maximum water holding capacity of 30.55%), ranging from 2.66% to 9.07%.

[0020] The main advantages of this invention are: 1. Using in-situ samples as inoculation materials and acclimating them in a simulated environment can maximize the adaptability of artificially cultivated biological crusts to the in-situ environment; 2. The nutrient solution is mainly formulated to meet the needs of cyanobacterial development, and the improvement of the water-holding capacity of biological crusts depends on the developmental state of cyanobacteria. The nutrient solution of this invention can maximize the development of cyanobacteria, thereby improving the maximum water-holding capacity of the crusts, reducing the need for the addition of other substances, saving cultivation costs, and reducing the impact and damage to the environment; 3. Currently, there are no specific nutrient solutions at home and abroad specifically designed to improve the maximum water-holding capacity of cyanobacterial crusts. This invention can fill the technological gap in this field.

[0021] This invention can be directly applied to the cultivation of in-situ cyanobacterial crusts and the improvement of their maximum water-holding capacity. It has a clear purpose and a relatively fast cultivation speed. It can be used for both in-situ cyanobacterial crusts and indoor artificial cyanobacterial crust cultivation, and has broad application value. Attached Figure Description

[0022] Figure 1 These are the phenotypic changes of artificially cultivated cyanobacterial crusts on day 1, day 60, and day 120 of cultivation.

[0023] Figure 2 It is the net increase in maximum water holding capacity at the end of cultivation, which is the combination of various nutrient formulas and inoculum amounts.

[0024] Figure 3 The results represent the artificial cyanobacterial crust development effect at the endpoint of the indoor cultivation effect test, including combination 31 and the optimal experimental combination K. Detailed Implementation

[0025] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0026] Example 1: Preparation of nutrient solution for targeted enhancement of the maximum water holding capacity of cyanobacterial crusts on coral islands

[0027] This invention discloses a method for the directional indoor cultivation of artificially cultivated cyanobacterial crusts with high water holding capacity, using a nutrient solution prepared with different concentrations of carbon, nitrogen, phosphorus, potassium, magnesium, and iron elements in a simulated natural coral island environment, combined with an optimal inoculum size, to ensure that cyanobacterial crusts derived from tropical coral island seed soil are cultured in a simulated natural coral island environment. The specific operation is carried out according to the following steps:

[0028] 1. Considering seven factors, including inoculum amount, glucose, sodium nitrate, disodium hydrogen phosphate, potassium chloride, magnesium chloride, and ferrous chloride, with four levels for each factor, a total of 32 different combinations of nutrient ratios and inoculum amounts were obtained using a seven-factor four-level orthogonal array. The specific concentrations and nutrient combinations are shown in Table 1 and Table 2, respectively.

[0029] Table 1. Types of nutrients and mineral elements and their corresponding concentrations and inoculum amounts.

[0030]

[0031] Table 2. Combinations of nutrient components and inoculum amounts generated using orthogonal arrays.

[0032]

[0033]

[0034]

[0035] 2. Treatment of inoculum material: Well-developed cyanobacterial crusts were collected from tropical coral islands and then naturally air-dried at room temperature (25℃). The air-dried cyanobacterial crusts were ground and prepared into experimental inoculum material for subsequent experiments.

[0036] 3. The calcareous sand collected in situ was placed into a cultivation box. The net weight of the sand was 1320g (dry weight) and the thickness was 35mm. The average moisture content of the calcareous sand was controlled at 14%, and the initial water addition was 220g. Then, the inoculation material was evenly spread on the calcareous sand using a self-made spraying device, and moistened with water mist to fix the inoculation material and start the cultivation.

[0037] 4. Based on long-term monitoring results of tropical coral islands, the artificial climate chamber temperature, relative humidity, photoperiod, and light intensity were set as follows (day / night): 33 / 28.5℃, 68% / 80%, 14 / 10h, and 13000 / 0 lux, respectively. Simultaneously, water loss was replenished daily to maintain the surface calcareous sand moisture content in the culture box at 14%. Twenty-four hours after the start of the experiment, 40 mL of a pre-prepared nutrient and mineral element mixture was evenly spread onto the substrate soil. Specific nutrient concentrations and inoculation amounts (calculated based on the amount of seed soil in the inoculation material) are detailed in Table 2.

[0038] 5. The artificial cultivation period was 120 days. Throughout the experiment, the artificially prepared nutrient solution was sprayed only once. After 120 days of indoor cultivation, obvious cyanobacterial crust formation was observed on the calcareous sand of all cultivation boxes. Figure 1 ).

[0039] 6. During the experiment, the maximum water-holding capacity of the crust sample was measured at the beginning and end of the experiment. The specific method is as follows:

[0040] Use a ring cutter (100cm) 3Collect biological crust samples and seal both ends. For testing, first remove the top and bottom covers of the ring cutter, replacing one end with a bottom cover with a mesh and filter paper, leaving the other end open. Then, place the end with the mesh and filter paper down into a porcelain dish (or flat-bottomed basin), filling and maintaining the water level in the dish up to the top edge of the ring cutter, allowing it to absorb water for 2 hours. At this point, all non-capillary and capillary pores in the soil in the ring cutter are filled with water. Replace the top cover, remove the cutter horizontally, and immediately place the end with the mesh and filter paper down into a flat-bottomed dish lined with dry sand to absorb excess water, then weigh it immediately (A). Finally, take a representative portion of the soil sample (20g) from the ring cutter and place it in an aluminum box to determine the soil moisture content. Use this soil moisture content to convert the wet soil in the ring cutter into the dry weight, and then calculate the maximum water holding capacity.

[0041] Maximum water holding capacity of biological crust % = (AWW ring) / W * 100%;

[0042] In the formula, W is the dry soil weight in the ring cutter (g); W_ring is the weight of the ring cutter (g).

[0043] The maximum water-holding capacity of artificial cyanobacterial crusts was determined and found to be ( Figure 2 The highest net increase was observed in treatment 31, at 7.08 ± 0.029%, but this was not significantly different from the net increases in experimental groups 3 and 5. In all experimental groups, the inoculum size was 240 g / m². 2 The experimental group showed the highest increase in average maximum water holding capacity, at 5.14 ± 1.44%. Analysis of variance of the orthogonal experimental results revealed four factors that significantly affected the water holding capacity of the samples (P < 0.05): sodium nitrate, sodium dihydrogen phosphate, potassium chloride, and inoculum size. Sodium nitrate had the greatest impact on the water holding capacity of the crust, while ferrous chloride had the least. The specific order of influence was: sodium nitrate > sodium dihydrogen phosphate > potassium chloride > inoculum size > glucose > magnesium chloride > ferrous chloride. Furthermore, the optimal concentration values ​​for each factor were: glucose concentration: T2 > T3 > T4 > T1; sodium nitrate concentration: T1 > T3 > T2 > T4; sodium dihydrogen phosphate concentration: T2 > T1 > T4 > T3; potassium chloride concentration: T1 > T4 > T3 > T2; magnesium chloride concentration: T1 > T3 > T2 > T4; ferrous chloride concentration: T3 > T1 > T4 > T2; inoculum size: T1 > T2 > T3 > T4. Therefore, in terms of maximum water holding capacity, the optimal combination of nutrient solutions for cultivating cyanobacteria crusts on coral islands to specifically enhance their maximum water holding capacity is: sodium nitrate concentration 0.1 g / L + sodium dihydrogen phosphate concentration 0.025 g / L + potassium chloride concentration 0.1 g / L + inoculum size 240 g / m³. 2 + Glucose concentration 25g / L + Magnesium chloride concentration 0.05g / L + Ferrous chloride concentration 0.005g / L.

[0044] Example 2: Indoor testing of the cultivation effect of nutrient solution

[0045] Indoor cultivation experiments were conducted according to steps 2-5 of Example 1. In the indoor testing experiments, there were two experimental groups, the combination of which was combination 31 from Example 1 (sodium nitrate concentration 0.1 g / L + sodium dihydrogen phosphate concentration 0.025 g / L + potassium chloride concentration 0.1 g / L + inoculum size 720 g / m²). 2 The experimental groups were: 1 group (25 g / L glucose, 0.1 g / L magnesium chloride, 0.005 g / L ferrous chloride) and 2 group K (0.1 g / L sodium nitrate, 0.025 g / L sodium dihydrogen phosphate, 0.1 g / L potassium chloride, 240 g / m³ inoculum) obtained through orthogonal experiment. 2 (Glucose concentration 25 g / L, magnesium chloride concentration 0.05 g / L, ferrous chloride concentration 0.005 g / L). The artificially prepared nutrient solution was sprayed only once throughout the experiment. The experimental period was 120 days, and the maximum water-holding capacity of the artificially prepared cyanobacterial crust was measured at the beginning and end of the experiment.

[0046] At the endpoint of the indoor cultivation effect test, the artificial cyanobacterial crust development effects of combination 31 and experimental combination K are shown in the figure. Figure 3 .

[0047] Analysis of the results of the indoor testing revealed that the average net increase in the maximum water holding capacity of combination 31 was 7.11 ±

[0048] The average net increase in the experimental group K was 0.53%, while the average net increase in the experimental group K was 7.19±0.89%, and there was no significant difference between the two experimental groups. However, the average value of the experimental group K was slightly higher than that of the experimental group 31. The maximum water holding capacity of the artificial cyanobacterial crust did not differ significantly between the two combinations, but the inoculum size of the experimental group K was much smaller. This indicates that the artificially prepared nutrient solution has a significant targeted promoting effect on the maximum water holding capacity of the artificial cyanobacterial crust, and can reduce the amount of environmental samples used, directly reducing environmental damage.

[0049] The nutrient solution provided by this invention can be used for both in situ cyanobacterial crust formation and indoor artificial cyanobacterial crust formation, thereby improving the freshwater storage capacity of coral islands and laying a good material foundation for the transformation of the coral island ecosystem. Therefore, this invention has broad application value.

[0050] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A cultivation nutrient solution suitable for increasing the maximum water holding capacity of a cyanobacterial crust on a coral island, characterized in that, The cultivation nutrient solution contains: glucose 25g / L, sodium dihydrogen phosphate 0.025g / L, potassium chloride 0.1g / L, magnesium chloride 0.05g / L, sodium nitrate 0.1g / L, ferrous chloride 0.005g / L, and the rest is water.

2. Use of the cultivation nutrient solution of claim 1 in fast cultivating cyanobacterial crust and / or increasing its maximum water holding capacity.

3. Use according to claim 2, characterized in that, The method comprises the following steps: a. The raw material is a coral island cyanobacterial crust grown on calcareous sand, which is naturally air-dried and then ground to make seed soil similar to the original biological crust community; b. The seed soil is evenly sowed and inoculated on calcareous sand for cultivation, and after the cultivation starts, at least one spraying of artificially prepared nutrient solution is performed, and the rest of the time, regular watering is performed to maintain the water content of the calcareous sand at 10% to 15%.

4. Use according to claim 3, characterized in that, In step a, the collected coral island cyanobacterial crust is air-dried at room temperature and then ground to make seed soil.

5. Use according to claim 3, characterized in that, In step b, the inoculation amount of the seed soil is 240 g / m 2 .

6. Use according to claim 3, characterized in that, In step b, the cultivation conditions are as follows: according to day / night, the temperature is 33 / 28.5℃, the relative air humidity is 68% / 80%, the light period is 14 / 10h, and the light intensity is 13000 / 0lux.

7. Use according to claim 3, characterized in that, In step b, the water content of the calcareous sand is maintained at 14%.

8. Use according to claim 3, characterized in that, In step b, after the seed soil is sprayed and fixed, the artificially prepared nutrient solution is sprayed only once. In step b, the water content of the calcareous sand is maintained at 14%.

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