Prediction of Aureococcus anophageffens using machine learning and deep learning.

The recurrent brown tide phenomenon, attributed to Aureococcus anophagefferens (A. anophagefferens), constitutes a significant threat to the Qinhuangdao sea area in China, leading to pronounced ecological degradation and substantial economic losses. This study utilized machine learning and deep learning techniques to predict A. anophagefferens population density, aiming to elucidate the occurrence mechanism and influencing factors of brown tide. Specifically, Random Forest (RF) algorithm was utilized to impute missing water quality data, facilitating its direct application in subsequent algal population prediction models. The results revealed that all four models-RF, Support Vector Regression (SVR), Multilayer Perceptron (MLP), and Convolutional Neural Network (CNN)-exhibited high accuracy in predicting A. anophagefferens population densities, with R2 values exceeding 0.75. RF, in particular, showed exceptional accuracy and reliability, with an R2 value surpassing 0.8. Additionally, the study ascertained five critical factors influencing A. anophagefferens population density: ammonia nitrogen, pH, total nitrogen, temperature, and silicate.

Significance of phosphate adsorbed on the cellular surface as a storage pool and its regulation in marine microalgae.

The increasing prevalence of phosphorus limitation in coastal waters has drawn attention to the bioavailability of cellular surface-adsorbed phosphorus (SP) as a reservoir of phosphorus in phytoplankton. This study examined the storage, utilization, and regulation of SP in the coastal waters of the East China Sea, as well as three cultivated algal bloom species (Skeletonema marinoi, Prorocentrum shikokuense, and Karenia mikimotoi) prevalent in the area. SP accounted for 14.3%-45.5% of particulate phosphorus in the field and laboratory species. After the depletion of external phosphate, the studied species can rapidly transport SP within 3-24 h. The storage of SP is regulated by both external phosphate conditions and the internal growth stage of cells, but it is not influenced by the various cellular surface structures of the studied species. This study highlights the significance of SP as a crucial phosphorus reservoir and the potential use of the SP level as an indicator of phosphorus deficiency in phytoplankton.

Triazine herbicide reduced the toxicity of the harmful dinoflagellate Karenia mikimotoi by impairing its photosynthetic systems.

Triazine herbicides are common contaminants in coastal waters, and they are recognized as inhibitors of photosystem II, causing significant hinderance to the growth and reproduction of phytoplankton. However, the influence of these herbicides on microalgal toxin production remains unclear. This study aimed to examine this relationship by conducting a comprehensive physiological and 4D label-free quantitative proteomic analysis on the harmful dinoflagellate Karenia mikimotoi in the presence of the triazine herbicide dipropetryn. The findings demonstrated a significant decrease in photosynthetic activity and pigment content, as well as reduced levels of unsaturated fatty acids, reactive oxygen species (ROS), and hemolytic toxins in K. mikimotoi when exposed to dipropetryn. The proteomic analysis revealed a down-regulation in proteins associated with photosynthesis, ROS response, and energy metabolism, such as fatty acid biosynthesis, chlorophyll metabolism, and nitrogen metabolism. In contrast, an up-regulation of proteins related to energy-producing processes, such as fatty acid ß-oxidation, glycolysis, and the tricarboxylic acid cycle, was observed. This study demonstrated that dipropetryn disrupts the photosynthetic systems of K. mikimotoi, resulting in a notable decrease in algal toxin production. These findings provide valuable insights into the underlying mechanisms of toxin production in toxigenic microalgae and explore the potential effect of herbicide pollution on harmful algal blooms in coastal environments.

Membrane lipid remodeling and autophagy to cope with phosphorus deficiency in the dinoflagellate Prorocentrum shikokuense.

Dinoflagellates, which are responsible for more than 80% of harmful algal blooms in coastal waters, are competitive in low-phosphate environments. However, the specific acclimated phosphorus strategies to adapt to phosphorus deficiency in dinoflagellates, particularly through intracellular phosphorus metabolism, remain largely unknown. Comprehensive physiological, biochemical, and transcriptomic analyses were conducted to investigate intracellular phosphorus modulation in a model dinoflagellate, Prorocentrum shikokuense, with a specific focus on membrane lipid remodeling and autophagy in response to phosphorus deficiency. Under phosphorus deficiency, P. shikokuense exhibited a preference to spare phospholipids with nonphospholipids. The major phospholipid classes of phosphatidylcholine and phosphatidylethanolamine decreased in content, whereas the betaine lipid class of diacylglyceryl carboxyhydroxymethylcholine increased in content. Furthermore, under phosphorus deficiency, P. shikokuense induced autophagy as a mechanism to conserve and recycle cellular phosphorus resources. The present study highlights the effective modulation of intracellular phosphorus in P. shikokuense through membrane phospholipid remodeling and autophagy and contributes to a comprehensive understanding of the acclimation strategies to low-phosphorus conditions in dinoflagellates.

Variation in intracellular polyphosphate and associated gene expression in response to different phosphorus conditions in the dinoflagellate Karenia mikimotoi.

Polyphosphate (polyP) has long been recognized as a crucial intracellular reservoir for phosphorus in microorganisms. However, the dynamics of polyP and its regulatory mechanism in eukaryotic phytoplankton in response to variations in external phosphorus conditions remain poorly understood. A comprehensive investigation was conducted to examine the intracellular polyP-associated metabolic response of the dinoflagellate Karenia mikimotoi, a harmful algal bloom species, through integrated physiological, biochemical, and transcriptional analyses under varying external phosphorus conditions. Comparable growth curves and Fv/Fm between phosphorus-replete conditions and phosphorus-depleted conditions suggested that K. mikimotoi has a strong capability to mobilize the intracellular phosphorus pool for growth under phosphorus deficiency. Intracellular phosphate (IPi) and polyP contributed approximately 6-23 % and 1-3 %, respectively, to the overall particulate phosphorus (PP) content under different phosphorus conditions. The significant decrease in PP and increase in polyP:PP suggested that cellular phosphorus components other than polyP are preferred for utilization under phosphorus deficiency. Genes involved in polyP synthesis and hydrolysis were upregulated to maintain phosphorus homeostasis in K. mikimotoi. These findings provide novel insights into the specific cellular strategies for phosphorus storage and the transcriptional response in intracellular polyP metabolism in K. mikimotoi. Additionally, these results also indicate that polyP may not play a crucial role in cellular phosphorus storage in phytoplankton, at least in dinoflagellates.

Efficient modulation of cellular phosphorus components in response to phosphorus deficiency in the dinoflagellate Karenia mikimotoi.

IMPORTANCE: Dinoflagellates are the most common phytoplankton group and account for more than 75% of harmful algal blooms in coastal waters. In recent decades, dinoflagellates seem to prevail in phosphate-depleted waters. However, the underlying acclimation mechanisms and competitive strategies of dinoflagellates in response to phosphorus deficiency are poorly understood, especially in terms of intracellular phosphorus modulation and recycling. Here, we focused on the response of intracellular phosphorus metabolism to phosphorus deficiency in the model dinoflagellate Karenia mikimotoi. Our work reveals the strong capability of K. mikimotoi to efficiently regulate intracellular phosphorus resources, particularly through membrane phospholipid remodeling and miRNA regulation of energy metabolism. Our research improved the understanding of intracellular phosphorus metabolism in marine phytoplankton and underscored the advantageous strategies of dinoflagellates in the efficient modulation of internal phosphorus resources to maintain active physiological activity and growth under unsuitable phosphorus conditions, which help them outcompete other species in coastal phosphate-depleted environments.

An overview of Prorocentrum donghaiense blooms in China: Species identification, occurrences, ecological consequences, and factors regulating prevalence.

Prorocentrum donghaiense Lu (also identified as Prorocentrum shikokuense Hada and Prorocentrum obtusidens Schiller) is a bloom-forming dinoflagellate species distributed worldwide. Blooms of P. donghaiense occur annually in adjacent waters of the East China Sea (ECS), especially in the waters near the Changjiang River Estuary. Blooms of this species have also been reported in nearby Japanese and Korean waters. There has been an apparent bloom-forming species succession pattern in the ECS since 2000, with diatom blooms in the early spring, shifting to long-lasting and large-scale dinoflagellate blooms dominated by P. donghaiense during the spring, and finally ended by diatom and/or Noctiluca scintillans blooms in summer. These bloom succession patterns were closely correlated with changes in environmental factors, such as temperature increase and anthropogenic eutrophication. Decreasing silicate by the construction of the Three Gorges Dam and increasing dissolved inorganic nitrogen flux were mainly influenced by high intensity human activities in the Changjiang River watershed, resulting in low Si/N ratio and high N/P ratios, possibly accelerating outbreak of P. donghaiense blooms. Phosphorous deficiency might be the most critical factor controlling the succession of microalgal blooms from diatoms to dinoflagellates. Prorocentrum donghaiense is a nontoxic species, but it can disrupt marine ecosystem by decreasing phytoplankton biodiversity and changing the structure of the food chain. Prorocentrum donghaiense blooms in the ECS have been intensively studied during the last two decades. Several possible mechanisms that contribute or trigger the annual blooms of this species have been proposed, but further research is required particularly on the aspect of nutrient budget, ecosystem impacts, as well as social-economic impact assessment.

Bioavailability of Organic Phosphorus Compounds to the Harmful Dinoflagellate Karenia mikimotoi.

Karenia mikimotoi is one of the most well-known harmful bloom species in temperate coastal waters. The present study investigated the characteristics of alkaline phosphatase (APase) and phosphodiesterase (PDEase) activities in hydrolysis of two phosphomonoesters (adenosine triphosphate (ATP) and ribulose 5-phosphate (R5P)) and a phosphodiester (cyclic adenosine monophosphate (cAMP)) in K. mikimotoi and compared its growth and physiological responses to the different forms of phosphorus substrates. K. mikimotoi produced comparable quantities of APase and PDEase to hydrolyze the organic phosphorus substrates, although hydrolysis of the phosphomonoesters was much faster than that of the phosphodiester. The growth of K. mikimotoi on organic phosphorus substrates was comparable to or better than that on inorganic phosphate. The difference in particulate organic nutrients (carbon, nitrogen, and phosphorus) and hemolytic activity supported different rates of hydrolysis-assimilation of the various organic phosphorus substrates by K. mikimotoi. The hemolytic activities of K. mikimotoi in the presence of organic phosphorus substrates were several times those in the presence of inorganic phosphate during the exponential phase. This suggested the potential important role of organic phosphorus in K. mikimotoi blooms.

Alkaline phosphatase activity during a phosphate replete dinoflagellate bloom caused by Prorocentrum obtusidens.

Prorocentrum obtusidens Schiller (formerly P. donghaiense Lu), a harmful algal species common in the East China Sea (ECS), often thrives with the depletion of phosphate. Three cruises in the spring of 2013 sampled an entire P. obtusidens bloom process to investigate the dynamics of alkaline phosphatase activity (APA) and phosphorus (P) status of the bloom species using both bulk and cell-specific assays. Unlike previous studies, the bloom of P. obtusidens occurred in a phosphate replete environment. Very high APA, with an average of 76.62 ± 90.24 nmol L-1 h-1, was observed during the early-bloom phase, a value comparable to that in low phosphate environments. The alkaline phosphatase (AP) hydrolytic kinetics also suggested a more efficient AP system with a lower half-saturation constant (Ks), but higher maximum potential hydrolytic velocity (Vmax) in this period. The APA decreased significantly with an average of 24.98 ± 30.98 nmol L-1 h-1 when the bloom reached its peak. The lack of a correlation between dissolved inorganic phosphate (DIP) or dissolved organic phosphate (DOP) concentration and APA suggested that the APA was regulated by the internal P growth demand, rather than the external P availability during the phosphate replete P. obtusidens bloom. These findings facilitate an understanding of the P. obtusidens acclimation strategy with respect to P variations in terms of AP expression during blooms in the ECS.

Temporal and spatial variations of alkaline phosphatase activity related to phosphorus status of phytoplankton in the East China Sea.

Phosphorus (P) is a potential limiting nutrient for primary production in the East China Sea (ECS). Four cruises over four seasons were conducted during 2009-2011 to evaluate the dynamics of alkaline phosphatase (AP) activity (APA) and the P status of phytoplankton in the ECS. Sampling for bulk and single-cell APA assays was performed across the ECS, which included the Changjiang River diluted water (CDW), the mid-shelf surface water (MSW), and the Kuroshio surface water (KSW) masses. The results showed that the distribution patterns of APA varied between water masses and with season. Higher APA was normally observed in the CDW, which was influenced by the Changjiang River plume. In the CDW, phytoplankton were P-stressed during the late spring with an average bulk APA of 20.4 ± 19.5 nmol h-1 L-1, which strengthened during the late summer (average APA maximizing at 106.2 ± 133.3 nmol h-1 L-1) and remained severe during the late autumn (average APA of 48.7 ± 34.1 nmol h-1 L-1) until reducing during the winter (average APA of 9.1 ± 13.6 nmol h-1 L-1). The variation patterns of APA and the P status of phytoplankton in the MSW were similar but with slight variations. In the KSW, a certain amount of APA occurred during the late spring and late autumn (averages of 18.7 ± 19.8 and 23.1 ± 18.7 nmol h-1 L-1, respectively). Single-cell APA coincided with the bulk APA to exhibit the temporal and spatial P-stress status of the dominant micro-phytoplankton. Phytoplankton were the main AP producers in the CDW, especially during the late summer, while pico-plankton contributed most to AP in the MSW and KSW. Our results suggest that phytoplankton suffer P-stress in most seasons, and emphasize the importance of AP in the recycling of organic P to support primary production in the P-deficient ECS.

Comparative uptake and assimilation of nitrate, ammonium, and urea by dinoflagellate Karenia mikimotoi and diatom Skeletonema costatum s.l. in the coastal waters of the East China Sea.

The nitrogen uptake kinetics and physiological growth of Karenia mikimotoi and Skeletonema costatum sensu lato grown on different N substrates and concentrations were compared in the laboratory. In the presence of three N substrates, both species preferred to take up NH4+. K. mikimotoi and S. costatum s.l. showed the highest substrate affinities for urea and NO3-, respectively. Both species grew well on three N substrates, and the growth parameters were comparable among the different N substrates. However, K. mikimotoi assimilated urea more efficiently than it assimilated either NO3- or NH4+. Different with S. costatum s.l., K. mikimotoi grew slowly and steady and the physiological and growth activities in N-depleted conditions were higher than those in N-replete conditions. Our results suggested that K. mikimotoi shows a greater readiness for uptake and assimilation of urea, and that this species is more competitive in an N-depleted environment when compared with S. costatum s.l.

Alkaline phosphatase activities and regulation in three harmful Prorocentrum species from the coastal waters of the East China Sea.

Harmful blooms of Prorocentrum donghaiense occur annually in the phosphorus-scarce coastal waters of the East China Sea (ECS). The enzymatic activities of alkaline phosphatase (AP) and its regulation by external phosphorus were studied during a P. donghaiense bloom in this area. The AP characteristics of P. donghaiense was further compared with Prorocentrum minimum and Prorocentrum micans in monocultures with both bulk and single-cell enzyme-labeled fluorescence AP assays. Concentrations of dissolved inorganic phosphorus (DIP) varied between 0.04 and 0.73 µmol l-1, with more than half recording stations registering concentrations below 0.10 µmol l-1. Concentrations of dissolved organic phosphorus (DOP) were comparable or even higher than those of DIP. P. donghaiense suffered phosphorus stress and expressed abundant AP, especially when DIP was lower than 0.10 µmol l-1. The AP activities showed a negative correlation with DIP but a positive correlation with DOP. The AP activities were also regulated by internal phosphorus pool. The sharp increase in AP activities was observed until cellular phosphorus was exhausted. Most AP of P. donghaiense was located on the cell surface and some were released into the water with time. Compared with P. minimum and P. micans, P. donghaiense showed a higher AP affinity for organic phosphorus substrates, a more efficient and energy-saving AP expression quantity as a response to phosphorus deficiency. The unique AP characteristic of P. donghaiense suggests that it benefits from the efficient utilization of DOP, and outcompete other species in the phosphorus-scarce ECS.

Light-harvesting protein Lhcx3 is essential for high light acclimation of Phaeodactylum tricornutum.

The light-harvesting protein complexes (Lhc) play key roles in the processes of light absorption and protection in diatoms. However, different Lhc protein carries out distinct function in photosynthesis. For now, roles of many Lhc proteins in light acclimation are largely unknown. Here, function of Lhcx3 in marine diatom Phaeodactylum tricornutum was examined by using reverse genetic technologies. The overexpression of Lhcx3 led to increased diadinoxanthin + diatoxanthin content and elevated non-photochemical fluorescence quenching (NPQ) while knockdown of Lhcx3 reduced NPQ level. In addition, the expression of Lhcx3 could be induced by blue light but not by red light. After addition of the photosynthetic inhibitor, upregulation of Lhcx3 transcript in high light could be inhibited by NH4Cl, but not by DCMU (3-(3,4-dichlorophenyl)-l,l-dim ethylurea). In contrast, DCMU addition increased expression of Lhcx3 in high light. In combination with changes of NPQ after addition of inhibitor, we concluded that the Lhcx3 played key roles in high light acclimation of diatoms. This finding will provide new clues for genetic improvement of P. tricornutum with an aim to cultivate new strains with high growth rate.

Transcriptome data of Prorocentrum donghaiense Lu under nitrogen and phosphorus limitation.

Prorocentrum donghaiense Lu is one of the most frequently occurred harmful algae in the coastal waters of China. The growth of P. donghaiense can be limited by nitrogen or phosphorus in marine environment. However, molecular mechanism of P. donghaiense in response to nitrogen and phosphorus limitation is poorly understood. In this study, we summarized the transcriptome datasets of P. donghaiense in response to nitrogen or phosphorus depletion. Raw data of approximately 19 GB in size were generated from IlluminaHiSeqTM 4000 sequencer. From 250, 539, 604 raw reads, 211, 394, 052 clean reads were obtained. The raw data were deposited into SRA database with the BioProject ID 436946. Our dataset will provide more scientific and valuable information for analyses of gene expression related to metabolic processes in P. donghaiense.

Significant activities of extracellular enzymes from a brown tide in the coastal waters of Qinhuangdao, China.

Brown tides of Aureococcus anophagefferens have occurred annually in the coastal waters of Qinhuangdao since 2009. High levels of dissolved organic matter (DOM) are always measured during bloom periods. Study focusing on the effect of DOM on the occurrences of brown tides in this area is scare by far. To analyze the efficiency of DOM hydrolysis by different groups of microorganisms and the possible influence of DOM on the formation of brown tides, extracellular enzymes such as α, ß-glucosidases (α, ß-GLUs), leucine aminopeptidase (LAP) and alkaline phosphatase (AP) as well as other environmental parameters were analyzed during a pre-bloom period of A. anophagefferens in June 2014. Dissolved organic nitrogen (DON) and phosphorus (DOP) contributed more than half of the total dissolved nutrient pools. Approximately 60-70% of the enzyme activities were associated with phytoplankton of size >5 µm. The hydrolysis rates of LAP were approximately 5 to 20 fold higher than those of AP and α, ß-GLUs. The ratios of ß-GLU activities: LAP activities indicated the hydrolysis potential related to proteins rather than polysaccharides. The differences in turnover time among the enzymes suggested that DOP was firstly hydrolyzed and recycled in the water in the early minutes, followed by the hydrolysis of DON and dissolved organic carbon (DOC)(in hours). Results suggest that the hydrolysis of DOM, in particular DOP, might significantly contribute to the occurrences of brown tides in the coastal waters of Qinhuangdao, China.

Relationship between phytoplankton community succession and environmental parameters in Qinhuangdao coastal areas, China: A region with recurrent brown tide outbreaks.

The picoplanktonic pelagophyte Aureococcus anophagefferens could trigger harmful algal blooms (HABs) to discolor water in brown, known as brown tide. Since 2009, large-scale brown tides, caused by A. anophagefferens, had been occurred in early summer for three consecutive years in the coastal waters of Qinhuangdao, China and resulted considerable deleterious effects on the scallop mariculture industry. The causes for the occurrence of brown tides were not fully understood. Therefore, we conducted a one-year survey from June 2013 to May 2014 to study the seasonal succession of the phytoplankton community, including A. anophagefferens and its relationship with environmental variables in the area. The results revealed that the population dynamics of the phytoplankton community were significant variation with seasonal succession, in which A. anophagefferens played an important role during the entire year. The trend of the whole diversity index indicated that the community structure became more stable in winter. The results of principle component analysis (PCA) applied to the environmental factors indicated four major seasonal groups in the environmental variables. The water temperature, silicate and total nitrogen were contributed to the environment in summer, autumn and spring, respectively. In addition, a few another environmental factors commonly contributed to the winter waterbody, indicated that the aquatic environment is more complex in the cold season. The result revealed that the phytoplankton community structure and its variation were mainly affected by the hydrological factors, by using the redundancy analysis (RDA) for the relationship between dominant species and the environment. Furthermore, we inferred Chaetoceros decipiens as a potential species for the breakout of harmful algae blooms (HABs) by RDA ordination. We concluded that the key factor for the seasonal variations in the dynamics of phytoplankton community could be the hydrological parameters in Qinghuangdao coastal area. This research may provide more insight into the occurrence mechanism of brown tide.

Metabolic and physiological changes in Prymnesium parvum when grown under, and grazing on prey of, variable nitrogen:phosphorus stoichiometry.

Mixotrophy is found in almost all classes of phytoplankton in a wide range of aquatic habitats ranging from oligotrophic to eutrophic marine and freshwater systems. Few studies have addressed how the nutritional status of the predator and/or the prey affects mixotrophic metabolism despite the realization that mixotrophy is important ecologically. Laboratory experiments were conducted to examine changes in growth rates and physiological states of the toxic haptophyte Prymnesium parvum when fed Rhodomonas salina of varying nutritional status. Haemolytic activity of P. parvum and prey mortality of R. salina were also measured. P. parvum cultures grown to be comparatively low in nitrogen (low-N), phosphorus (low-P) or low in both nutrients (low-NP) were mixed with low-NP, low-N, and low-P R. salina in all possible combinations, i.e., a 3×3 factorial design. N deficiency was obtained in the low-N cultures, while true P deficiency may not have been obtained in the low-P cultures. Mortality rates of R. salina (both due to ingestion and/or cell rupture as a function of grazing or toxic effects) were higher when R. salina cells were low-P, N-rich, regardless of the nutritional state of P. parvum. Mortality rates were, however, directly related to the initial prey:predator cell ratios. On the other hand, growth of the predator was a function of nutritional status and a significant positive correlation was observed between growth rates of P. parvum and cell-specific depletion rates of N, whereas no such relationship was found between P. parvum growth rates and depletion rates of P. In addition, the greatest changes in chlorophyll content and stoichiometric ratios of P. parvum were observed in high N:P conditions. Therefore, P. parvum may show enhanced success under conditions of higher inorganic N:P, which are likely favored in the future due to increases in eutrophication and altered nutrient stoichiometry driven by anthropogenic nutrient loads that are increasingly enriched in N relative to P.

Allocation Costs Associated with Induced Defense in Phaeocystis globosa (Prymnesiophyceae): the Effects of Nutrient Availability.

Colony enlargement in Phaeocystis globosa has been considered as an induced defense strategy that reduces its susceptibility to grazers, but allocation costs inflicted by this plastic morphological defense are poorly understood. We conducted experiments in which P. globosa cultures were exposed to chemical cues from copepods, ciliates and heterotrophic dinoflagellates, respectively, under nutrient sufficient and deficient conditions to evaluate allocation costs associated with induced defense. Phaeocystis globosa responded to chemical cues from grazers by increasing colony diameter irrespective of nutrient conditions. We did not find trade-offs between induced defense and growth rate under nutrient sufficient conditions. Instead, induced defensive P. globosa had higher growth rates than non-induced P. globosa. When nutrient became limited, P. globosa exposed to grazing cues from copepods and dinoflagellates had significantly decreased growth rates when compared with non-induced P. globosa. We suggested that the decreased growth revealed allocation costs associated with induced defense that may influence on the trophic interactions between Phaeocystis and consumers.

Bioavailability of dissolved organic phosphorus compounds to typical harmful dinoflagellate Prorocentrum donghaiense Lu.

The bioavailability of dissolved organic phosphorus (DOP) compounds to harmful alga Prorocentrum donghaiense Lu and its alkaline phosphatase activity (APA) were studied. Results showed that P. donghaiense could utilize the test DOP compounds such as glucose-6-phosphate (G-6-P), adenosine triphosphate (ATP) and ribonucleic acid (RNA) to sustain its growth. Nutrition between the test DOP compounds and orthophosphate was comparable. P. donghaiense could utilize intracellular phosphorus to sustain growth under depletion of dissolved phosphorus. Variation of APA in different test DOP compounds was addressed; the controlling mechanism of APA in different DOP media was discussed.

[Advances in researches of aquatic ectoenzyme and its relationship with red tide].

Ectoenzymes play an important role in the material cycle and energy conversion in aquatic ecosystem. The researches of ectoenzyme are of significance in further understanding the marine carbon biogeochemical cycle and the countermeasures of algae under bloom conditions. In this paper, the research methods, characteristic activity and size distribution, controlling factors and their ecological significances of algal ectoenzymes were reviewed, and ectoenzyme introduced as one kind of new trophic state index.