Method for detecting death state of algae

Abstract

The invention provides a method for detecting the death state of algae, which comprises an apparent morphology observation procedure, a chlorophyll a content determination procedure, a scanning electron microscope determination procedure and a judgment procedure, and when the apparent morphology of algae liquid to be detected is judged to be abnormal, the content of chlorophyll a is lower than the lowest detection limit and the microstructure is incomplete, the algae liquid to be detected is judged to be abnormal. Or when the apparent morphology of the to-be-detected algae liquid is normal, the content of chlorophyll a is lower than the minimum detection limit and the microstructure is incomplete, or when the apparent morphology of the to-be-detected algae liquid is abnormal, the content of chlorophyll a is not lower than the minimum detection limit and the microstructure is incomplete, the to-be-detected algae liquid is judged to be dead, otherwise, the to-be-detected algae liquid has activity. According to the detection method, the death state of the algae can be detected from multiple angles, the accuracy is high, the efficiency is high, the detection method is a non-invasive or slightly invasive method, additional damage to cells caused by manual treatment can be avoided, and the detection result is closer to the real death state of the algae in the natural environment.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental monitoring and pollution control, and in particular to a method for detecting the death state of algae. Background Art

[0002] Algae play a key role in ecosystems, particularly in aquatic environments. They are not only fundamental producers but also indicators of water quality and environmental changes. The survival and reproduction of algae are crucial to the stability and self-purification capacity of aquatic ecosystems. Algal die-off is often accompanied by deteriorating environmental conditions, such as nutrient overload and pollutant accumulation. Therefore, accurately detecting algal die-off status can help understand the health of water bodies.

[0003] At present, the mainstream methods for indoor detection of algae death status are as follows:

[0004] (1) Microscope observation: directly observing the morphological changes of algae cells through a microscope. However, in the actual operation process, the inventors found that this method has the following problems: First, for phytoplankton samples containing cell clusters, ultrasonic treatment is required to disperse the cell clusters before dilution, which is complicated to operate; second, this method also requires multiple steps such as fixation, precipitation, concentration, and microscopic observation, which makes the entire detection process labor-intensive and time-consuming (more than 48 hours), affecting the timeliness of the detection; third, for some algae, such as cyanobacteria such as Microcystis aeruginosa, because their cells are small, it is difficult to distinguish the dead and alive states of algae cells through a microscope; fourth, due to the depth of field limitation of the microscope, different algae cells in the same field of view may be located on different focal planes, resulting in different clear areas and blurred areas in each microscopic image collected, which may make the observation results inaccurate.

[0005] (2) Staining methods mainly use different dyes (such as trypan blue, fluorescent dyes, etc.) to stain the algae and then observe their activity status. Although the staining method is relatively fast, the selection of dyes and the optimization of staining conditions are very important. Slight deviations may lead to inaccurate results. In addition, some dyes may be toxic to algae, affecting the accuracy of activity judgment.

[0006] (3) Fluorescence microscopy: Fluorescence microscopy uses fluorescent dyes to label specific intracellular substances, such as DNA or cell membranes, and determines cell death by the intensity of fluorescence. This method can effectively distinguish between active and inactive cells, but fluorescence microscopy equipment is expensive and technically demanding, making it unsuitable for large-scale application. In addition, the choice and concentration of fluorescent dyes can also affect detection accuracy.

[0007] (4) Optical density measurement (OD method) is mainly used to detect changes in algal cell density. This method does not directly detect the state of death, but indirectly reflects it through density changes. Changes in optical density may be affected by other environmental factors, leading to misjudgment, especially when the algae are under stress or partially dead, the error is large.

[0008] (5) Biochemical detection method: By detecting biochemical substances in algae cells, such as chlorophyll content and protein degradation products, the survival status of algae can be determined. However, the biochemical method is relatively complex and time-consuming, requiring the extraction of internal cell substances and high requirements for experimental conditions. At the same time, because the biochemical composition is greatly affected by the environment, it may have changed before death, making the results difficult to be accurate.

[0009] (6) ATP activity measurement. ATP is the energy source of all living cells. Measuring the ATP content in algae cells can determine their activity status. Generally, a decrease in ATP content is a sign of cell death. ATP activity measurement requires specialized equipment and expensive reagents. At the same time, fluctuations in cell activity do not completely represent cell death. False positives or false negatives may occur, especially when cells are slightly damaged but not dead.

[0010] In summary, existing methods for detecting algae mortality have shortcomings in terms of technical requirements, detection efficiency, subjectivity, and cost. Therefore, it is necessary to improve the accuracy and efficiency of algae mortality detection. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a method for detecting the death state of algae with high accuracy and efficiency.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0013] A method for detecting the death state of algae comprises a morphological observation step, a chlorophyll a content determination step, a scanning electron microscope determination step, and a determination step, wherein:

[0014] The morphology observation step includes observing the morphology of the algae solution to be tested;

[0015] The chlorophyll a content determination step includes determining the chlorophyll a content of the algae liquid to be measured;

[0016] The scanning electron microscope measurement process includes observing the microstructure of the algae liquid to be measured using a scanning electron microscope;

[0017] The determination step includes determining whether the appearance of the algae solution to be tested is normal, determining whether the chlorophyll a content of the algae solution to be tested is lower than the minimum detection limit, and determining whether the microstructure of the algae solution to be tested is intact.

[0018] When it is determined that the appearance of the algae liquid to be tested is abnormal, the chlorophyll a content is lower than the minimum detection limit, and the microstructure is incomplete, or when it is determined that the appearance of the algae liquid to be tested is normal, the chlorophyll a content is lower than the minimum detection limit, and the microstructure is incomplete, or when it is determined that the appearance of the algae liquid to be tested is abnormal, the chlorophyll a content is not lower than the minimum detection limit, and the microstructure is incomplete, the algae liquid to be tested is determined to be dead; otherwise, the algae liquid to be tested is active.

[0019] Preferably, the apparent morphology includes color, distribution state and precipitation state. When the color is dark green, yellow or brown, or the distribution is uneven, or there are flocs or precipitation, the apparent morphology is determined to be abnormal, otherwise the apparent morphology is determined to be normal.

[0020] Preferably, the minimum detection limit is 0.1 μg / L.

[0021] Preferably, the microstructure includes cell membrane, cell wall and organelles. When the cell membrane is ruptured, twisted or shrunk, or the cell wall is incomplete or concave, or the organelles or intracellular melt flow out, the microstructure is determined to be incomplete; otherwise, the microstructure is determined to be complete.

[0022] Preferably, the chlorophyll a content of the algae liquid to be tested is determined by planktonic fluorescence method.

[0023] In some embodiments, the planktonic fluorescence method includes sampling the algal solution to be tested, filtering the sample, and using a planktonic fluorescence instrument to detect the chlorophyll a content of the sample and the filtrate, respectively. The difference between the two is the chlorophyll a content of the algal solution to be tested.

[0024] Preferably, the algae solution to be tested is randomly sampled to obtain n groups of samples, where n ≥ 2. The microstructure of the samples is observed using a scanning electron microscope. If the microstructures of all n groups of samples are incomplete, the microstructure of the algae solution to be tested is determined to be incomplete; otherwise, the microstructure of the algae solution to be tested is determined to be complete. By randomly sampling two or more groups of samples, the accuracy of sampling is further increased.

[0025] Further preferably, random sampling is performed in different areas of the algae liquid to be tested.

[0026] In some embodiments, the magnification of the scanning electron microscope is 1000 to 20000 times.

[0027] Preferably, the determination step further comprises determining that the algae liquid to be tested is in a stress response state when the apparent morphology of the algae liquid to be tested is abnormal, the chlorophyll a content is not lower than the minimum detection limit, and the microstructure is intact.

[0028] Furthermore, when the appearance of the algae liquid to be tested is abnormal in color, such as dark green, yellow, or brown, the environment in which the algae liquid to be tested is located has high salt or extreme pH.

[0029] Furthermore, when the apparent morphology of the algae liquid to be tested is unevenly distributed, or floccules or sediments are present, the algae cells have an aggregation effect.

[0030] Preferably, when the apparent morphology of the algae liquid to be tested is normal, the content of chlorophyll a is lower than the minimum detection limit, and the microstructure is intact, it is determined that the algae liquid to be tested is in a dormant state or has entered apoptosis.

[0031] Preferably, when the apparent morphology of the algae liquid to be tested is normal, the content of chlorophyll a is not lower than the minimum detection limit, and the microstructure is incomplete, it is determined that the algae liquid to be tested is in a stress response state.

[0032] Preferably, the algae liquid to be tested is a mixed algae liquid containing at least two algae species.

[0033] Preferably, the detection method includes first performing the apparent morphology observation step, and then performing the chlorophyll a content determination step and / or the scanning electron microscopy determination step.

[0034] Further preferably, after the morphological observation step, it is determined whether the morphological appearance of the algae liquid to be tested is normal. When the morphological appearance is normal, one or both of the chlorophyll a content determination step and the scanning electron microscopy determination step are selectively performed. When the morphological appearance is abnormal, the chlorophyll a content determination step is performed, followed by the scanning electron microscopy determination step.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The detection method of the present invention can detect the death status of algae from multiple angles with high accuracy and efficiency. Compared with traditional heating, chemical and other methods that will destroy the appearance and morphology of algae cells, this detection method is a non-invasive or slightly invasive method, which can avoid additional damage to cells caused by human processing, making the detection results closer to the actual state of algae death in the natural environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Microscope images of algae in Lake Taihu before and after death. The left image shows living algae, and the right image shows dead algae after 15 days of dark culture.

[0038] Figure 2 Images of algae in Lake Taihu before and after death. The left image shows living algae, and the right image shows dead algae after 15 days of dark culture.

[0039] Figure 3These are scanning electron microscope images of Taihu algae before and after death. The upper image shows living algae, and the lower image shows dead algae after 15 days of dark culture. DETAILED DESCRIPTION

[0040] During the early stages of exploration, the inventors visually inspected the morphology of the algae culture solution, such as color, distribution, and turbidity, to determine the physiological state of the algae and whether it was inactivated. Living algae are usually emerald green, mainly because they contain a large amount of chlorophyll-a (Chl-a). After the algae die, the chlorophyll will gradually decompose, and the color may change to dark green, yellow, or even brown. Healthy algae are usually evenly distributed in the water, suspended or moving freely; inactivated algae will aggregate into flocs and settle, forming distinct stratification in the water. The dark green, yellow, or even brown color of the algae culture solution, as well as the presence of algae flocs and sediments, can, to a certain extent, represent the death state of the algae.

[0041] However, further research by the inventors revealed that this detection method carries a significant risk of misjudgment. For example, in the later stages of growth, algal cell division slows, reducing the synthesis of photosynthetic pigments and gradually consuming chlorophyll, which can also manifest as a change in algal color. However, the algal cells may simply be gradually entering a state of apoptosis or dormancy, and not completely losing activity. Furthermore, under stressful conditions (such as changes in salinity or pH), the pigments within algal cells may also change, resulting in a color change. This change may be an adaptive response to the adverse environment and does not necessarily indicate death. (Red and brown algae exhibit pigment changes under high salinity or extreme pH conditions. For example, certain species of brown algae can cause the algal fluid to change color due to environmental stimuli. This phenomenon is often mistakenly attributed to pigment degradation caused by algal death, but in reality, the cells may simply be in a state of stress response.) For another example, when algae are cultured at high density, cells may aggregate due to the high density, resulting in the formation of precipitates. In this case, algal cells (cyanobacteria, such as Microcystis aeruginosa) may aggregate at the bottom of the culture vessel, forming a visible precipitate, but they are still active cells. Therefore, the above detection method has a large error. In addition, for mixed algae liquid, the apparent morphological changes before and after death are not obvious.

[0042] The inventors also used a microscope (optical microscope or fluorescence microscope) to observe and confirm the death of algae during the exploration process, but Figure 1 As shown, microscopic observations only reveal the fragmentation of some larger algae, while the morphological changes of smaller algae, such as Microcystis aeruginosa, cannot be observed. Furthermore, because the mixed algae sample was taken from Taihu Lake, it contained many impurities, making identification difficult.

[0043] In summary, accurately determining the mortality state of algae, especially mixed algae, presents challenges. After extensive research, the inventors have demonstrated that the mortality state of mixed algae can be accurately determined through morphological observation combined with Chl-a content measurement and scanning electron microscopy. This invention is further described below.

[0044] A method for detecting the death state of algae comprises a morphological observation step, a chlorophyll a content determination step, a scanning electron microscope determination step, and a determination step.

[0045] The morphological observation step involves observing the morphology of the algae solution to be tested. Specifically, visual observation can be used to observe the morphology of the algae solution to be tested. The morphology includes color, distribution, and sedimentation. Color is categorized as emerald green, dark green, yellow, and brown; distribution is categorized as uniform or uneven; and sedimentation is categorized as either the absence or presence of flocs or sediment.

[0046] The chlorophyll a content determination process involves measuring the chlorophyll a content of the algae solution to be tested. Specifically, the chlorophyll a content can be tested using the planktonic fluorescence method, which is simple and convenient.

[0047] The scanning electron microscopy (SEM) measurement process involves observing the microstructure of the algae solution under test using a scanning electron microscope (SEM). This microstructure includes the cell membrane, cell wall, and organelles. Cell membranes are classified as intact, ruptured, distorted, or shrunken; cell walls are classified as intact and non-depressed, intact but depressed, or incomplete; and organelles are classified as either without internal fusion outflow or with internal fusion outflow. Specifically, n groups of samples (n ≥ 2) are randomly selected from different regions of the algae solution under test and their microstructures are observed using a SEM.

[0048] The determination process includes determining whether the surface morphology of the algae solution to be tested is normal, determining whether the chlorophyll a content of the algae solution to be tested is lower than the minimum detection limit (the minimum detection limit is 0.1 μg / L), and determining whether the microstructure of the algae solution to be tested is complete (when the microstructures of n groups of samples are all incomplete, the microstructure of the algae solution to be tested is determined to be incomplete).

[0049] When the appearance of the algae liquid to be tested is determined to be abnormal, the chlorophyll a content is lower than the minimum detection limit, and the microstructure is incomplete, or when the appearance of the algae liquid to be tested is determined to be normal, the chlorophyll a content is lower than the minimum detection limit, and the microstructure is incomplete, or when the appearance of the algae liquid to be tested is determined to be abnormal, the chlorophyll a content is not lower than the minimum detection limit, and the microstructure is incomplete, the algae liquid to be tested is determined to be dead; otherwise, the algae liquid to be tested is active.

[0050] Furthermore, if the algae solution's morphology is abnormal, the chlorophyll a content is at least the minimum detection limit, and the microstructure is intact, the algae solution is considered to be in a stress state. Under stressful conditions (such as changes in salinity or pH), pigments within algae cells may change, resulting in color changes. This change may be an adaptive response to adverse conditions and does not necessarily indicate cell death.

[0051] When the algae solution tested appears normal, the chlorophyll a content is below the minimum detection limit, and the microstructure is intact, the algae solution is considered dormant or has entered apoptosis. During the aging phase of the algae life cycle, algae gradually consume chlorophyll a, resulting in a decrease in chlorophyll content. For example, in late-stage algae culture, chlorophyll a content gradually decreases, but some cells still maintain a certain level of activity. This is because the algae's cell division rate slows in the late stages of growth, reducing the synthesis of photosynthetic pigments and gradually consuming chlorophyll. This natural aging process does not necessarily mean immediate death.

[0052] The algal solution is considered to be in a stress state when its apparent morphology is normal, its chlorophyll a content is at least the minimum detection limit, and its microstructure is incomplete. Under unfavorable environmental conditions, such as insufficient light, low temperature, and high salinity, algal cells may exhibit significant morphological changes, such as cell shrinkage, surface depressions, and cell membrane deformation, which can be observed using SEM. However, these changes are a stress response and do not indicate cell death. Algae can adapt to adverse environments by adjusting their metabolic activity and return to normal morphology when conditions improve. Therefore, algae under stress may exhibit structural characteristics similar to those of dead cells under SEM, but in reality, they are still alive.

[0053] The present method, which combines algal morphological observation, chlorophyll a content measurement, and scanning electron microscopy, offers significant advantages in assessing algal mortality. Compared to traditional or mainstream laboratory simulation methods, it provides more comprehensive and accurate information on algal mortality. This detection method more accurately and realistically reflects algal mortality and cellular structural changes. Its advantages lie in refined morphological observation, non-destructive detection of the mortality process, and comprehensive integration of physiological and morphological information. This provides richer evidence of mortality, making it suitable for in-depth research on the natural mortality process of algae and enabling multi-faceted mortality assessment at the cellular, morphological, and physiological levels. Accurately detecting algal mortality contributes to understanding the health of water bodies and is crucial for controlling algal blooms.

[0054] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0055] Hereinafter, unless otherwise specified, the algae solution to be tested was taken from Taihu Lake and cultured in a dark environment for 15 days to kill the algae. The death state of the algae solution before and after death was tested.

[0056] Example 1

[0057] A method for detecting the death state of algae comprises the following steps:

[0058] (1) Apparent morphology observation process: Observe the apparent morphology of the algae solution to be tested. The algae solution to be tested is observed visually. The apparent morphology includes color, distribution state, and sedimentation state. When the color is dark green, yellow, or brown, or the distribution is uneven, or there are flocs or sediments, the apparent morphology is judged to be abnormal; otherwise, the apparent morphology is judged to be normal, that is, when the color is emerald green, the distribution is uniform, and there are no flocs or sediments, the apparent morphology is normal.

[0059] (2) Chlorophyll a content determination process: The chlorophyll a content of the algae solution to be tested is determined and compared with the minimum detection limit (0.1 μg / L). The chlorophyll a content is tested using the planktonic fluorescence method. Some samples have strong background fluorescence that can affect the measurement results. Some samples have excessive dissolved organic matter, and the fluorescence emitted by the dissolved organic matter can also interfere with the measurement results. Therefore, it is necessary to filter the sample and use the filtrate as a blank sample to eliminate these effects. It is preferred to use a 0.4-0.5 μm micropore filter to filter the sample. This example specifically uses a planktonic fluorometer (Phyto-PAM) to measure the chlorophyll a content of the algae liquid sample and its filtrate. The specific steps include: checking the instrument connection, turning it on after connection, and opening the PhytoWin software; removing the sample cup, adding 1-2 mL of sample (the volume should be consistent each time), closing the lid, and dark adapting; setting Meas.Freq. to 32 in the Settings window, switching to the Channels window, clicking Chl[MF32], and measuring the chlorophyll a concentration; switching to the Light Curve window, clicking Start to measure the light response curve; changing the sample and continuing the measurement; after the measurement is completed, switching to the Report window, clicking File / Save Report, and storing the data.

[0060] (3) Scanning electron microscopy measurement process: The microstructure of the algae solution to be tested is observed using a scanning electron microscope. The microstructure includes cell membranes, cell walls, and organelles. Specifically, three groups of samples are randomly selected from the upper, middle, and lower regions of the algae solution to be tested, and the three groups of samples are placed on the stage of the scanning electron microscope. The magnification is 5 μm, and scanning electron microscope images of the samples are obtained. If the scanning electron microscope images of the three groups of samples all show cell membrane rupture, distortion, or contraction, or incomplete or concave cell walls, or organelles or intracellular melt outflow, the microstructure of the algae solution to be tested is determined to be incomplete; otherwise, the microstructure of the algae oil to be tested is determined to be complete.

[0061] (4) Judgment process: When the appearance of the algae solution to be tested is judged to be abnormal, the chlorophyll a content is lower than the minimum detection limit, and the microstructure is incomplete, or when the appearance of the algae solution to be tested is judged to be normal, the chlorophyll a content is lower than the minimum detection limit, and the microstructure is incomplete, or when the appearance of the algae solution to be tested is judged to be abnormal, the chlorophyll a content is not lower than the minimum detection limit, and the microstructure is incomplete, the algae solution to be tested is judged to be dead, otherwise the algae solution to be tested is active.

[0062] like Figure 2 and Figure 3 As shown in the figure, before the death treatment, the algae samples to be tested were emerald green, evenly distributed, without flocs or sediments, and had normal appearance. The chlorophyll a content was higher than the minimum detection limit. The algae cells in the scanning electron microscope images of the three groups of samples were intact, indicating that the algae samples to be tested were active. After the death treatment, the algae samples to be tested were emerald green but unevenly distributed, with flocs and sediments, and had abnormal appearance. The chlorophyll a content was lower than the minimum detection limit. The algae cells in the scanning electron microscope images of the three groups of samples showed varying degrees of damage, as shown in the figure. Figure 3 As shown in the red circle, it means that the algae sample to be tested is dead, which is consistent with the actual result, indicating that the accuracy of the method of the present invention is high.

[0063] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for detecting the death state of algae, characterized in that: The detection method comprises an apparent morphology observation step, a chlorophyll a content determination step, a scanning electron microscope determination step and a determination step, wherein: The apparent morphology observation step includes observing the apparent morphology of the algae solution to be tested; The chlorophyll a content determination step includes determining the chlorophyll a content of the algae liquid to be determined; The scanning electron microscope determination process includes observing the microstructure of the algae liquid to be measured using a scanning electron microscope; The determination step includes determining whether the apparent morphology of the algae solution to be tested is normal, determining whether the chlorophyll a content of the algae solution to be tested is lower than the minimum detection limit, and determining whether the microstructure of the algae solution to be tested is intact. When it is determined that the apparent morphology of the algae liquid to be tested is abnormal, the content of chlorophyll a is lower than the minimum detection limit and the microstructure is incomplete, or when it is determined that the apparent morphology of the algae liquid to be tested is normal, the content of chlorophyll a is lower than the minimum detection limit and the microstructure is incomplete, or when it is determined that the apparent morphology of the algae liquid to be tested is abnormal, the content of chlorophyll a is not lower than the minimum detection limit and the microstructure is incomplete, the algae liquid to be tested is determined to be dead, otherwise the algae liquid to be tested is active.

2. The method for detecting the death state of algae according to claim 1, characterized in that: The apparent morphology includes color, distribution state and precipitation state. When the color is dark green, yellow or brown, or the distribution is uneven, or there are floccules or precipitation, the apparent morphology is determined to be abnormal, otherwise the apparent morphology is determined to be normal; and / or, The minimum detection limit is 0.1 μg / L; and / or, The microstructure includes cell membrane, cell wall and organelles. When the cell membrane is ruptured, twisted or shrunk, or the cell wall is incomplete or concave, or the organelles or intracellular fusion flows out, the microstructure is determined to be incomplete, otherwise the microstructure is determined to be complete.

3. The method for detecting the death state of algae according to claim 1, characterized in that: The chlorophyll a content of the algae solution to be tested is determined by planktonic fluorescence method.

4. The method for detecting the death state of algae according to claim 3, characterized in that: The planktonic fluorescence method includes sampling the algae solution to be tested, filtering the sample, and using a planktonic fluorescence instrument to detect the chlorophyll a content of the sample and the filtrate respectively, and the difference between the two is the chlorophyll a content of the algae solution to be tested.

5. The method for detecting the death state of algae according to claim 1, characterized in that: Randomly sample the algae liquid to be tested to obtain n groups of samples, where n≥2, and observe the microstructure of the samples using the scanning electron microscope. When the microstructures of the n groups of samples are all incomplete, it is determined that the microstructure of the algae liquid to be tested is incomplete; otherwise, it is determined that the microstructure of the algae liquid to be tested is complete.

6. The method for detecting the death state of algae according to claim 5, characterized in that: The magnification of the scanning electron microscope is 1000 to 20000 times.

7. The method for detecting the death state of algae according to claim 1, characterized in that: The determination step further includes determining that the algae liquid to be tested is in a stress response state when the apparent morphology of the algae liquid to be tested is abnormal, the content of chlorophyll a is not lower than the minimum detection limit, and the microstructure is intact; and / or, When the apparent morphology of the algae solution to be tested is normal, the content of chlorophyll a is lower than the minimum detection limit and the microstructure is intact, it is determined that the algae solution to be tested is in a dormant state or has entered apoptosis; and / or, When the apparent morphology of the algae liquid to be tested is normal, the content of chlorophyll a is not lower than the minimum detection limit, and the microstructure is incomplete, it is determined that the algae liquid to be tested is in a stress response state.

8. The method for detecting the death state of algae according to claim 1, characterized in that: The algae liquid to be tested is a mixed algae liquid containing at least two algae species.

9. The method for detecting the death state of algae according to claim 1, characterized in that: The detection method comprises firstly performing the apparent morphology observation step, and then performing the chlorophyll a content determination step and / or the scanning electron microscope determination step.

10. The method for detecting the death state of algae according to claim 9, characterized in that: After the apparent morphology observation step, it is determined whether the apparent morphology of the algae liquid to be tested is normal. When the apparent morphology is normal, one or both of the chlorophyll a content determination step and the scanning electron microscope determination step are selectively performed; when the apparent morphology is abnormal, the chlorophyll a content determination step is performed, and then the scanning electron microscope determination step is performed.

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