Phaeocystis Globosa Research Articles

Quercetin Enhanced Cellulose Nanocrystals for the Removal of Harmful Algae Phaeocystis Globosa

The Phaeocystis globosa widely exists in the seawater, which becomes a great threat for the health of humans and animals in the ecological ecosystem. In this work, we reported a promising control strategy with quercetin(QT) enhanced cellulose nanocrystals (CNC). The quercetin enhanced cellulose nanocrystals (QT/CNC) was characterized through Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectrometer (FTIR) and X-ray diffractometer (XRD). The effects of concentrations of CNC and QT on controlled Phaeocystis globosa were investigated. The results showed that the removal rate of Phaeocystis globosa exhibited an optimal value (92.1 %) at 0.05 g L-1 CNC and 0.1 g L-1 QT. Furthermore, the chlorophyll-a content in the Phaeocystis globosa exhibited a remarkable decrease from 3.72 mg L-1 to 0.21 mg L-1 when QT/CNC was interacted. On the basis of these results, we concluded that Phaeocystis globosa could be removed by QT/CNC effectively. During the removal of Phaeocystis globosa, the pH of algal solution decreased from 9.45 to 7.36, indicating that QT/CNC could maintain the normal pH of water. In addition, the testing result of the QT/CNC zeta potentials was negative, which revealed that Phaeocystis globosa was removed through inhibition and flocculation. Accordingly, a possible removal mechanism of Phaeocystis globose by QT/CNC was presumed. This study suggested that QT/CNC might be a potential treatment materials on the removal of Phaeocystis globosa.

Removal effect of algicidal modified clay on Phaeocystis globosa blooms in culturing enclosure experiments: A short communication

With the increased scale of marine aquaculture in the Beibu Gulf, as well as accelerating urbanization and industrialization, frequent harmful algal blooms (HABs) have occurred in this area, especially those formed by Phaeocystis globosa in the past several years. As the P. globosa bloom has been a serious marine ecological disaster in the Beibu Gulf, research on quick and effective methods to eliminate P. globosa blooms is a hot research topic. In this study, the bacteria Streptomyces yatensis B4503 combined with modified diatomite was used to prepare algicidal modified clay, which was then used to study the removal effect on P. globosa blooms in field culture enclosures. The results showed that after 6 h of treatment with algicidal modified clay, compared with the blank control group, the cell density and chlorophyll a content of P. globosa decreased by 26.86% and 64.03%, respectively, and they decreased by 75.23% and 84.81%, respectively, after 24 h. The study indicated that algicidal modified clay can be applied to eliminate HABs caused by P. globosa in coastal water.

Effects of Modified Clay on Phaeocystis globosa Growth and Colony Formation.

Phaeocystis globosa is a globally distributed harmful algal blooms (HABs) species dominated by the colonial morphotype, which presents dramatic environmental hazards and poses a threat to human health. Modified clay (MC) can effectively flocculate HAB organisms and prevent their subsequent growth, but the effects of MC on colony-dominated P. globosa blooms remain uncertain. In this paper, a series of removal and incubation experiments were conducted to investigate the growth, colony formation and colony development of P. globosa cells after treatment with MC. The results show that the density of colonies was higher at MC concentrations below 0.2 g/L compared to those in the control, indicating the role of P. globosa colonies in resistance to environmental stress. Concentrations of MC greater than 0.2 g/L could reduce the density of solitary cells and colonies, and the colony diameter and extracellular polysaccharide (EPS) content were also decreased. The adsorption of MC to dissolved inorganic phosphorus (DIP) and the cell damage caused by collision may be the main mechanisms underlying this phenomenon. These results elucidate that the treatment with an appropriate concentration of MC may provide an effective mitigation strategy for P. globosa blooms by preventing their growth and colony formation.

Harmful algal blooms caused by Phaeocystis globosa from 1997 to 2018 in Chinese coastal waters

From 1997 to 2018, Phaeocystis globosa caused harmful algal blooms in Chinese coastal waters almost every year. In this study, the spatial and temporal distribution of P. globosa blooms and its influencing factors were discussed. The results showed that 80.6% of the P. globosa blooms happened in the South China Sea and 72.5% happened in the period from November to March of the following year. But in the Yellow Sea, P. globosa blooms might be limited by green tides. Among the influencing factors, temperature might be an important one that affected the spatial and temporal distribution of P. globosa blooms. Furthermore, eutrophication provided material basis and El Nino events might also stimulate the occurrence of P. globosa blooms. This study is helpful to reveal causes and mechanisms of P. globosa blooms and reduce the negative impacts of blooms on ecological environment, economic development and the safety of nuclear power plants.

Bacterial Composition Associated With Giant Colonies of the Harmful Algal Species Phaeocystis globosa.

The cosmopolitan algae Phaeocystis globosa forms harmful algal blooms frequently in a number of tropical and subtropical coastal regions in the past two decades. During the bloom, the giant colony, which is formed by P. globosa, is the dominant morphotype. However, the microenvironment and the microbial composition in the intracolonial fluid are poorly understood. Here, we used high-throughput 16S rRNA amplicon sequencing to examine the bacterial composition and predicted functions in intracolonial fluid. Compared with the bacterial consortia in ambient seawater, intracolonial fluids possessed the lower levels of microbial richness and diversity, implying selectivity of bacteria by the unique intracolonial microenvironment enclosed within the P. globosa polysaccharide envelope. The bacterial consortia in intracolonial fluid were dominated by Balneola (48.6% of total abundance) and Labrezia (28.5%). The bacteria and microbial function enriched in intracolonial fluid were involved in aromatic benzenoid compounds degradation, DMSP and DMS production and consumption, and antibacterial compounds synthesis. We suggest that the P. globosa colonial envelope allows for the formation of a specific microenvironment; thus, the unique microbial consortia inhabiting intracolonial fluid has close interaction with P. globosa cells, which may benefit colony development.

Co-occurrence of chromophytic phytoplankton and the Vibrio community during Phaeocystis globosa blooms in the Beibu Gulf

Accumulating research evidence has revealed that harmful algal blooms (HABs) can substantially affect the community structures of phytoplankton and heterotrophic bacteria in marine ecosystems. However, little is known about their species-specific interactions between phytoplankton and heterotrophic bacteria during the HABs period and about their interaction shifts in response to blooms. From this perspective, we investigated the co-occurrence of chromophytic phytoplankton and Vibrio during Phaeocystis globosa blooms in the Beibu Gulf. The results showed that Vibrio communities were distinct during the blooms, and P. globosa blooms resulted in a decline in phytoplankton alpha diversity, revealing that the blooms could affect their community compositions. The regression lines between the Shannon indices and Bray-Curtis distances of phytoplankton and Vibrio showed positive correlations with each other (p < 0.001), suggesting that they may have intrageneric symbiotic interactions overall. In addition, network analysis further demonstrated that relationships between phytoplankton and Vibrio were dominated by positive correlations, and more interaction modules were observed during the blooms, revealing that the blooms intensified synergistic association and mutual symbiotic interactions between them. Environmental factors (SiO32-, NH4+, NO3- and TN,) and P. globosa density more deeply affected network interactions between phytoplankton and Vibrio during the periods of P. globosa blooms than those before the blooms and after the blooms. This study provided new insight to elucidate community structure and interaction relationships between phytoplankton and Vibrio in response to P. globosa blooms and their ecological effects in marine ecosystems.

CHEMTAX analysis of phytoplankton assemblages revealed potential indicators for blooms of haptophyte Phaeocystis globosa

Harmful algal blooms formed by the haptophyte Phaeocystis globosa have been recorded in the Beibu Gulf since 2011. In this study, the composition and variation of phytoplankton assemblages in the Beibu Gulf were studied during an intense bloom of P. globosa from 2016 to 2017, using the CHEMTAX approach. In phytoplankton samples collected from the Beibu Gulf, chlorophyll a (Chl a, 0.046–2.87 μg L−1) and fucoxanthin (Fuco, 0.041–13.7 μg L−1) were the most abundant pigments. Diatoms were the dominant group of phytoplankton, followed by cyanobacteria (mainly Synechococcus), haptophytes, cryptophytes, prasinophytes, dinoflagellates, and chlorophytes. Phytoplankton samples were clustered into four communities characterized by diatoms, cyanobacteria, haptophytes containing 19′-butanoyloxyfucoxanthin (the “Hapt-But” subgroup of haptophytes), and haptophytes containing 19'-hexanoyloxyfucoxanthin (the “Hapt-Hex” subgroup of haptophytes). Distribution pattern of the “Hapt-But” subgroup of haptophyte was consistent with that of P. globosa colonies. Diatoms had positive correlation with P. globosa colony abundance, while cyanobacteria had negative correlation. The diagnostic pigments for colony-forming P. globosa (But-fuco), diatoms (Fuco) and cyanobacteria (zeaxanthin), as well as temperature (<20 °C), could serve as potential early-warning indicators for the formation of P. globosa blooms in the Beibu Gulf.

Response of dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) cell quotas to oxidative stress in three phytoplankton species

Abstract Several phytoplankton species produce the metabolites dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) but their intracellular roles need to be better understood. To improve the understanding of the DMSP antioxidant function suggested by Sunda et al. (2002), we exposed the diatom Skeletonema costatum, the Prymnesiophyceae Phaeocystis globosa and the dinoflagellate Heterocapsa triquetra to experimental treatments known to cause potential oxidative stress (high light intensities (HL); HL with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU); menadione sodium bisulfite (MSB)). DMSP and DMSO concentrations decreased after 6 h in all treatments indicating an interaction with Reactive Oxygen Species (ROS) produced. DMSP and DMSO-to-cell ratios in control conditions were higher for H. triquetra, while being unable to grow under HL. DMSP and DMSO-to-cell carbon were the highest for P. globosa, while the other species had similar values. During long-term treatment, these ratios were not increased in high-light grown cells of P. globosa and S. costatum. Overall, this illustrates that (1) the DMSP- and DMSO-to-cell or carbon seems to be not indicative of the capability of the species to tolerate an oxidative stress, (2) these molecules could react with ROS and lower their cellular concentration, but no clues demonstrated that these molecules are part of the antioxidant response of the cell.

Cloning and heterologous expression of a UDP-sugar-producing pyrophosphorylase gene from the harmful alga Phaeocystis globosa (Prymnesiophyceae) and its possible function in colony formation

Massive Phaeocystis globosa blooms have caused serious damage to coastal Chinese marine ecosystems. Previous studies have shown that colony formation, a unique phenotypic characteristic of P. globosa, is accompanied by the up-regulation of USP (Uridine-diphosphate sugar pyrophosphorylase) genes. UDP-sugar-producing pyrophosphorylases are important enzymes involved in glucose metabolism. In this study, a novel UDPase protein, PgUSP, was identified in P. globosa that comprised a uridine binding motif and a pyrophosphorylase consensus motif. PgUSP encodes a novel polypeptide that localizes within the nucleus of cells. Moreover, exopolysaccharide production increased when PgUSP was transformed into Escherichia coli for over expression analysis. Further, we observed that the number and sizes of P. globosa colonies were significantly larger in cultures treated with cell-free filtrates of the diatom Chaetoceros affinis, while PgUSP expression was significantly up-regulated compared to that of the control without filtrate addition. These results indicate that expression of PgUSP can promote exopolysaccharide production and thus play an important role in P. globosa colony formation.

Differences Between Solitary Cells and Colonial Cells in the Heteromorphic Life Cycle of Phaeocystis globosa: Morphology, Physiology, and Transcriptome

Differences Between Solitary Cells and Colonial Cells in the Heteromorphic Life Cycle of Phaeocystis globosa: Morphology, Physiology, and Transcriptome

Large Differences in the Haptophyte Phaeocystis globosa Mitochondrial Genomes Driven by Repeat Amplifications.

The haptophyte Phaeocystis globosa is a well-known species for its pivotal role in global carbon and sulfur cycles and for its capability of forming harmful algal blooms (HABs) with serious ecological consequences. Its mitochondrial genome (mtDNA) sequence has been reported in 2014 but it remains incomplete due to its long repeat sequences. In this study, we constructed the first full-length mtDNA of P. globosa, which was a circular genome with a size of 43,585 bp by applying the PacBio single molecular sequencing method. The mtDNA of this P. globosa strain (CNS00066), which was isolated from the Beibu Gulf, China, encoded 19 protein-coding genes (PCGs), 25 tRNA genes, and two rRNA genes. It contained two large repeat regions of 6.7 kb and ∼14.0 kb in length, respectively. The combined length of these two repeat regions, which were missing from the previous mtDNA assembly, accounted for almost half of the entire mtDNA and represented the longest repeat region among all sequenced haptophyte mtDNAs. In this study, we tested the hypothesis that repeat unit amplification is a driving force for different mtDNA sizes. Comparative analysis of mtDNAs of five additional P. globosa strains (four strains obtained in this study, and one strain previously published) revealed that all six mtDNAs shared identical numbers of genes but with dramatically different repeat regions. A homologous repeat unit was identified but with hugely different numbers of copies in all P. globosa strains. Thus, repeat amplification may represent an important driving force of mtDNA evolution in P. globosa.

High genetic diversity of the harmful algal bloom species Phaeocystis globosa revealed using the molecular marker COX1

Accumulating evidence indicates that the haptophyte species Phaeocystis globosa, which plays an important role in climate control and may cause harmful algal blooms (HABs), displays a rich genetic diversity that may be responsible for differences in colonial sizes, different toxicity during blooms, and differential optimum growth temperature. In this project, we demonstrated that COX1 can be used as an effective molecular marker for its low intra-genome variations and high resolution in differentiating different P. globosa strains. Analyzing 57 P. globosa strains and seven field samples revealed high P. globosa genetic diversity with at least seven distinct clades. This study not only demonstrated for the first time that the common molecular marker COX1 can be used for differentiating P. globosa strains with high-resolution, and for tracking dynamics of different P. globosa strains during bloom development, but also revealed that P. globosa had high genetic diversity in the field.

Research on the biology and ecology of the harmful algal bloom species Phaeocystis globosa in China: Progresses in the last 20 years

Chinese researchers have made substantial progresses in research on the harmful algal bloom (HAB) species Phaeocystis globosa since the first P. globosa bloom outbreak in the Chinese coastal waters in 1997. However, as many results, especially the earlier ones, were published in non-English literature, much of the research on P. globosa biology, ecology, and biogeochemistry made by Chinese researchers have been unknown to colleagues from other countries. We review current knowledge on taxonomy, morphology, genetics, physiology, survival strategies and mitigation of P. globosa gained by Chinese researchers from the past two decades. P. globosa is the only Phaeocystis species that causes blooms in the Chinese waters, although other Phaeocystis species including P. jahnii and P. cordata have been detected in Chinese coastal regions. P. globosa has a complex life history with at least two morphotypes including a haploid flagellate and a diploid colonial cell. Colonial P. globosa blooms typically occur in winter after a diatom bloom in coastal waters of the South China Sea. P. globosa in Chinese coastal waters usually has extremely large colonial sizes, up to 3 cm in diameter, an order of magnitude greater than that observed in European coastal waters. The development of giant colonies is associated with enhanced sinking rate, limited nutrient diffusion, as well as decreased stability of colonies. The Chinese P. globosa strains also showed strong genetic diversity and physiological plasticity, being able to grow and develop into colonies at higher temperature and irradiance relative to that in European waters. High genetic diversity of P. globosa was revealed by developing high-resolution and high-specificity molecular markers including Phaeocystis globosa chloroplast 1 (pgcp1). Due to the severe impact of P. globosa on ecology and economy, much effort has been made to mitigate P. globosa blooms including the application of modified clays. Overall, P. globosa in the Chinese waters demonstrate unique genetic, phenotypical and physiological features that differ from P. globosa in other ocean regions. Further studies are needed to explore how environmental factors trigger the occurrence of P. globosa blooms and ascertain the impact of P. globosa blooms on the environment.

Metagenomic phage biodiversity: New insight into the tropical estuarine ecosystem process and microbial risk assessment

Viruses infecting unicellular organisms were shown to have a significant influence on aquatic ecosystem processes. Their role in biogeochemical cycles, primary production and microbial risk assessment in the tropical estuarine systems remain unresolved. The present study is the first approach of Next Generation Sequence (NGS) based viral metagenomic analysis of Cochin estuarine sediment. Viral particles were purified from 1.5 kg sediment samples collected from Cochin estuary, employing flocculation, and the purity was confirmed using epifluorescence microscopy. The flocculate was subjected to whole genome amplification using Illumina. Present NGS data provides information about the abundance of major bacteriophages, especially, cyanophages which play a significant role in ecosystem engineering and the biogeochemical cycle. In the present study, bacteriophages such as phages of Aeromonas, Bacillus, Salmonella, Vibrio, Burkholderia, Acanthocystis turfacea, Acidianus, Clostridium and Escherichia represented a major fraction. NGS result confirmed Aeromonas phages (19.78%) to be the most abundant communities present in the Cochin estuarine sediment. Cyanophages and phytoplankton attacking phage communities included A. turfacea virus, Chlorella virus, Acidianus filamentous virus, Ectocarpus siliculosus virus, Phaeocystis globosa virus, Chrysochromulina ericina virus, Emiliania huxleyi virus, Micromonas pusilla virus, Ostreococcus lucimarinus virus, Ostreococcus tauri virus, Synechococcus virus and Prochlorococcus virus. Unicellular photosynthetic Synechococcus and Prochlorococcus, abundant in oceans and estuaries, contribute to a substantial proportion of primary productivity, so the presence of these low-light adapted cyanobacteria attacking phages in estuarine sediments reveals that they are the key factor that controls the primary production and are also essential in preventing pathogenic bacterial population explosions. The data can be used as a road map for modelling efforts to link the role of viruses in determining carbon and nutrient availability in tropical estuarine ecosystems and the microbial risk assessment.

Inelastic hyperspectral Scheimpflug lidar for microalgae classification and quantification.

An inelastic hyperspectral Scheimpflug lidar system was developed for microalgae classification and quantification. The correction for the refraction at the air-glass-water interface was established, making our system suitable for aquatic environments. The fluorescence spectrum of microalgae was extracted by principal component analysis, and seven species of microalgae from different phyla have been classified. It was verified that when the cell density of Phaeocystis globosa was in the range of ${{1}}{{{0}}^4}\sim{{1}}{{{0}}^6}\;{\rm{cell}}\;{\rm{m}}{{\rm{L}}^{- 1}}$, the cell density had a linear relationship with the fluorescence intensity. The experimental results show our system can identify and quantify microalgae, with application prospects for microalgae monitoring in the field environment and early warning of red tides or algal blooms.

Screening and isolation of glyceroglycolipids with antialgal activity from several marine macroalgae

Glyceroglycolipids and antialgal activity were used as the main indexes to identify the glyceroglycolipid extracts of marine macroalgae with significant antialgal activity from 6 species of marine macroalgae—Codium fragile, Neoporphyra haitanensis, Sargassum fusiforme, Saccharina japonica, Silvetia siliquosa and Undaria pinnatifida. The extracts of all tested algae contained glyceroglycolipids and exhibited antialgal activity against Karenia mikimotoi and Phaeocystis globosa. Further, by antialgal activity bioassay-guided fractionation method in combination with extraction and partitioning as well as multi-chromatography, two glyceroglycolipids with antialgal activity, 1-O-palmitoyl-3-O-β-D-galactopyranosyl glycerol and 1-O-palmitoyl-2-O-oleoyl-3-O-β-D-galactopyranosyl glycerol, were isolated for the first time from N. haitanensis and S. siliquosa, respectively. There were no glyceroglycolipids with antialgal activity in the other four macroalgae.

The effect of Ditylum brightwellii (Bacillariophyceae) on colony development of bloom forming species Phaeocystis globosa (Prymnesiophyceae) under nutrient-replete condition

To improve our knowledge of the factors regulating Phaeocystis globosa colony formation, the effects of the diatom Ditylum brightwellii on P. globosa colony development were investigated using co-culture and cell-free filtrate approaches. The co-culture experiments showed the moderate abundance of D. brightwellii significantly increased the number and size of colonies, whereas a dramatically decreased effect from high abundance of D. brightwellii. The low abundance of D. brightwellii promoted early formation of P. globosa colony. The cell-free filtrate experiments indicated that culture-filtrates from the exponential phase of D. brightwellii were stimulatory for P. globosa colony formation with more and bigger colonies formed, whereas an inhibitory effect from its senescence phase filtrates. D. brightwellii may influence P. globosa colony formation by regulating the growth of P. globosa solitary cells. Our results suggest that D. brightwellii influences P. globosa colony development, but its effects vary according to its concentrations and growth phases.

Induced Allelopathic Effects of Thalassiosira weissflogii on Colony Formation in Phaeocystis globosa

Co-culturing and using cell-free filtrates are common methods for investigating allelopathy of marine phytoplankton; however, these methods often yield inconsistent or even contradictory results. The induced release of allelopathic compounds has been hypothesized as a mechanism to explain the discrepancy. Here, we used experiments to assess the inducibility of allelopathy by the diatom, Thalassiosira weissflogii, on the colony formation of Phaeocystis globosa. T. weissflogii and its cell-free filtrates showed inhibitory effects on the growth of solitary P. globosa cells. The colony number, colony diameter, and cells per colony decreased by co-occurring T. weissflogii cells but were enhanced by their extracellular filtrates alone. Living T. weissflogii cells possibly affect the colony integrity by reducing colonial cell density of P. globosa. When P. globosa and T. weissflogii were co-cultured but separated with a 2-µm membrane filter, thus allowing the exchange of extracellular secretions without direct cell contact, P. globosa colony concentration, colony diameter, cells per colony and colonial cell density were inhibited. Once T. weissflogii cells were pre-exposed to cell-free filtrates of P. globosa, their filtrates inhibited colony formation. T. weissflogii had allelopathic effects on P. globosa by releasing extracellular compounds that inhibited growth of solitary cells and colony formation, as well as disrupting colony integrity. However, the allelopathic effects of T. weissflogii on colony formation were only induced when the presence of P. globosa was perceived. Chemically mediated allelopathic effects of diatoms on colony formation of P. globosa may play an important role in the succession of diatoms and Phaeocystis.

Prokaryotic community composition and structure during Phaeocystis globosa blooms in the Beibu Gulf, China

Phaeocystis globosa blooms have become one of the major ecological issues in the Beibu Gulf, China, in recent years, resulting in a series of negative impacts on local fisheries and industry. While prokaryotes play key roles in nutrient cycling and energy flow during algal blooms, information regarding the response of the prokaryotic community during Phaeocystis blooms remains scarce. Thus, a comprehensive field study covering the onset and senescent phase of P. globosa blooms was conducted in the area from December 2016 to February 2017. The community composition was revealed with high-throughput sequencing of the 16S rRNA gene. A total of 7426 operational taxonomic units (OTUs) (97% similarity) were identified from 3132328 effective tags, with Proteobacteria, Cyanobacteria, Thaumarchaeota, Verrucomicrobia, Euryarchaeota, Actinobacteria, and Bacteroidetes being the predominant taxa. The composition and structure of particle-attached (PA) and free-living (FL) prokaryotic communities were significantly different: the PA fraction was more diverse and unstable temporally compared to the FL fraction. Variations in the composition and structure of the prokaryotic community were closely associated with major environmental variables, particularly dissolved oxygen (DO), NH4+, PO43-, and dissolved organic carbon (DOC). The presence of P. globosa may result in differences in the prokaryotic community; members of Rhodobacteraceae, Alteromonadales, Porticoccaceae, Vibrio, Flavobacteriales, and Verrucomicrobiae were the key taxa in the prokaryotic communities during the outbreak and senescent phases of P. globosa blooms. This study provides primary information on the response of prokaryotic communities during P. globosa blooms and will facilitate further study on biogeochemical processes of algal-derived organic matter in the tropical gulf.

Spatiotemporal dynamics of marine microbial communities following a Phaeocystis bloom: biogeography and co-occurrence patterns.

Marine microbes play important roles in the development of phytoplankton blooms. The diversity and composition of free living (FL) and particle attached (PA) microbial communities have been well studied, while little is known about their geographic and co-occurrence patterns, especially during the subsiding process of Phaeocystis globosa blooms. Herein, the beta-diversity of FL and PA microbial communities in both the surface and bottom layers of different habitats were comprehensively examined during succession of a P. globosa bloom event. The results showed that microbial communities from bloom and non-bloom sites exhibited distinct community compositions. Among the different sampling sites, the community similarities decreased with spatial distance, in which the FL communities' similarity in bottom waters was more influenced by spatial variation. The variation of microbial communities was mostly attributed to environmental selection, spatial distance, and the abundance of P. globosa successively. The co-occurrence networks of microbial communities in bloom and non-bloom waters differed in terms of structure and composition, and the bloom network had more links and closer relationships between genera than the non-bloom network. The correlation among genera and modules suggested that the bloom microbes were likely driven by high environmental selection and low competitive effect between each other.