Variation Of Phytoplankton Community Research Articles

Cross-domain diversity effects: linking diatom species richness, intraspecific richness, and biomass production to host-associated bacterial diversity

Abstract Interactions between bacteria and microalgae are important for the functioning of aquatic ecosystems, yet interactions based on the biodiversity of these two taxonomic domains have been scarcely studied. Specifically, it is unclear whether a positive biodiversity-productivity relationship in phytoplankton is largely facilitated by niche partitioning among the phytoplankton organisms themselves, or whether associated bacterial communities play an additional role in modifying these diversity effects. Moreover, effects of intraspecific diversity in phytoplankton communities on bacterial community diversity have not been tested. To address these points, we factorially manipulated both species and intraspecific richness of three diatoms to test effects of diatom species/strain diversity on biomass production and bacterial diversity in algae-bacteria communities. The results show that diatom intraspecific diversity has significant positive effects on culture biomass and the diversity of the associated free-living bacterial community (0.2-3 μm size fraction), which are comparable in magnitude to species diversity effects. However, there were little to no effects of diatom diversity on host-associated bacterial diversity (>3 μm size fraction), or of bacterial diversity on biomass production. These results suggest a decoupling of bacterial diversity from the diatom diversity-productivity relationship and provide early insights regarding the relations between diversity across domains in aquatic ecosystems.

Plankton Diversity and Hydro-biological Parameters at Wazirabad Barrage in Yamuna River

This study conducted a comprehensive investigation into the qualitative and quantitative analysis of plankton diversity and Physico-chemical water quality parameters in the Yamuna River. Samples were collected from the Wazirabad barrage from June 2022 to November 2022, revealing a diverse phytoplankton community consisting of 50 genera distributed across five major classes. The abundant classes were Bacillariophyceae, with 18 genera, followed by Chlorophyceae with 20 genera, Cyanophyceae with 9 genera, Euglenophyceae with 2 genera, and Dianophyceae represented by a single genus. The qualitative analysis uncovered a zooplankton community with 20 genera from Protozoa and Rotifera, Copepoda, and Cladocera. Protozoa were represented by two genera, Copepods exhibited eight genera, Cladocera included five genera, and Rotifera featured four genera. The most abundant class of phytoplankton is Chlorophyceae and Zooplankton is Copepods. Physico chemical water quality parameters more fluctuation during the study period. These findings offer valuable insights into the biodiversity and composition of phytoplankton and zooplankton communities in the Wazirabad Barrage ecosystem.

Twenty-six years of phytoplankton pigments reveal a circumpolar Class Divide around the Southern Ocean

Regional taxonomic variation of phytoplankton communities in the Southern Ocean remains largely uncharacterised despite the distinct trophic and biogeochemical roles of different taxa in anthropogenic carbon uptake, biogeochemical processes, and as the primary source of energy for marine ecosystems. Here we analysed 26 years of pigment data (14,824 samples between 32°S and the Antarctic coast) from over 50 voyages (1996 – 2022), using the phytoclass software. The analysis confirms that the Antarctic Polar Front (APF) is a circumpolar phytoplankton class boundary, separating haptophyte dominated communities to the north from diatom domination of chlorophyll a in the south, and thereby a biological analogue corresponding to the Biogeochemical Divide. Furthermore, community composition was remarkably similar in different zones south of the APF despite substantial spatial variation in biomass. This circumpolar characterisation of the geospatial distribution of phytoplankton community composition will contribute to improved modelling and projection of future change in ecosystems and carbon in the Southern Ocean.

Diversidade, dominância e raridade da comunidade fitoplanctônica: um estudo de caso em lagos urbanos tropicais

Abstract Aim The aim of this study was to evaluate how phytoplankton community diversity, dominance, and rarity are influenced by different local environmental conditions in urban lakes. We expect that richness will be negatively influenced in lakes with higher nutrient concentrations and high turbidity, while abundance will be positively influenced. Thus, lakes with these conditions will have greater dominance of a few species and lower rarity, and the opposite in lakes with lower nutrient concentrations and less turbidity. Methods Phytoplankton and abiotic variables samples were collected in fourteen lakes distributed in the municipality of Goiânia, Goiás, Brazil, during a rainy period. Results It was possible to identify an environmental heterogeneity among the lakes. We identified a separation of the lakes according to phytoplankton richness and density, especially due to the contribution of green algae, desmids, and cyanobacteria. Most lakes showed high diversity and evenness values, with a predominance of rare taxa and few dominant species. The main variables associated with phytoplankton were water temperature, dissolved oxygen, turbidity, and nutrient concentrations. Conclusions Therefore, the study of species diversity, dominance, and rarity based on phytoplankton richness and abundance and their relationship with different local environmental conditions can be an important model for assessing water quality in urban lakes.

Spatio-temporal dynamics of phytoplankton in a diversion reservoir and the major influencing factors: taxonomic versus functional groups classification.

Identifying factors affecting phytoplankton dynamics is crucial to the management of aquatic ecosystems. A lot of scholars have conducted intensive studies on phytoplankton in lake or reservoirs, but not many studies have been conducted on diversion reservoirs. To explore the seasonal and spatial variation of phytoplankton communities and their relationship with environmental factors in the context of water diversion, a case study was carried out at XiKeng (XK) reservoir in South China. In this study, month-by-month water samples and phytoplankton were collected from this reservoir from December, 2021, to July, 2022. The results showed that the phytoplankton community was characterized by significant spatial and temporal variations. There were significant differences in phytoplankton abundance and structure in the reservoirs in terms of time. The abundance of phytoplankton cells and the proportion of Cyanobacteria in the reservoir showed a trend of increasing from autumn to spring and then decreasing from spring to summer, while the functional group evolved from S1 in autumn to SN in spring and summer. The abundance of phytoplankton was influenced by the dynamic water division and the characteristics of the reservoir itself, resulting in a spatial distribution characteristic of AIII > AII > AI. Water temperature (WT) and nutrients were the key factors driving the changes in phytoplankton abundance and community structure in the reservoir. These findings will deepen our understanding of the spatial and temporal dynamics of phytoplankton community structure in diversion reservoirs and provide a basis for freshwater water ecological management strategies.

Environmental DNA detects biodiversity and ecological features of phytoplankton communities in Mediterranean transitional waters

Climate changes and anthropogenic pressures are causing a biodiversity decline in terms of species number and genetic diversity, reducing the adaptability and evolvability of natural communities. Transitional water ecosystems are more sensitive to habitat reduction and degradation and, thus, are more exposed to biodiversity declines requiring biodiversity monitoring programs for their conservation. Environmental DNA (eDNA) metabarcoding represents a high-throughput tool for biodiversity assessment that is facilitating data collection for biodiversity monitoring. In this study, we applied, for the first time, eDNA metabarcoding in a Mediterranean coastal lagoon to assess the ecological features of eukaryotic phytoplankton communities. We sampled water in seven different lagoon sites and amplified the extracted DNA with primers targeting the variable region 4 (V4) of the 18S rRNA gene marker. The results demonstrated the validity of eDNA studies to provide insights into lagoon phytoplankton composition, establish the structure and spatial variation of phytoplankton communities, and evaluate its correlation to abiotic factors. Finally, the genetic distances analysis suggests that the different spatial distribution of OTUs, at least for the Tetraselmis genus, reflects the genetic background.

Distribution and trophic functioning of planktonic communities in coastal marshes in Atlantic Coast of France

Coastal marshes are submitted to huge management due to anthropogenic pressure and thus, it is essential to preserve their biodiversity, their ecological functions and the ecosystem services they can provide. This study investigates the diversity and abundance of planktonic communities (heterotrophic prokaryotes, heterotrophic protists, microphytoplankton and metazooplankton). The aim of this study is to provide a first quantitative inventory on the plankton communities present in two marshes and to construct the different typologies of planktonic food webs in these marshes. Seasonal samplings (4) for environmental variables, nutrient concentrations and planktonic communities were conducted at 2–3 stations on each marsh during a year. A total of five different types of planktonic food web were determined, three of them were found in both marshes. The saltmarsh phytoplanktonic communities were dominated by Cryptophyta, nanoflagellates and Cyanobacteria. The freshwater marsh was dominated by Cryptophyta in autumn and winter and by a diverse phytoplankton community in spring. Marine copepods (Calanoida and Harpacticoida) characterized the saltwater metazooplanktonic communities, Cladocerans and Rotifera the freshwater ones. Overall, the planktonic diversity was higher in the freshwater marsh (102 taxa) than in the saltwater marsh (54 taxa).Phytoplankton blooms represented nutrient and CO2 uptake in both marshes and this purification function seemed most efficient in autumn in the saltmarsh. Considerable zooplankton communities represented a potential for nursery. Of the three management actions performed, only periodic water renewals might affect the seasonal dynamics of planktonic communities.

Spatiotemporal variation of phytoplankton communities and water quality among seaweed, shellfish and cage fish culture systems

Various marine aquaculture systems have different impacts on the environment, but few assessments were focused on the environmental impact by different systems in the same region. To study the effects of various aquaculture systems on phytoplankton community structure and water properties, 5 surveys were carried out in seaweed (Gracilaria lemaneiformis, GL), shellfish (Mytilus coruscus, MC) and cage fish (Larimichthys crocea, LC) mariculture areas in Dongji island, Zhejiang, China from June to September 2020. Significant differences were observed in some environmental parameters and phytoplankton communities among three aquaculture systems. The dissolved oxygen concentrations and Secchi depth in the surface waters in GL area were relatively higher than in the blank and other areas. As for nutrients concentration, LC and MC areas had higher concentrations than blank area, while GL area was the lowest. Though Chlorophyll-a concentration displayed fluctuations, relatively lower concentrations were found in GL area. Shannon diversity index was found to be relatively constant and higher in GL area. The Non-metric multidimensional scaling results revealed that phytoplankton composition had a distinct pattern among sampling times. The correlations and Redundancy analysis showed that total nitrogen, salinity and transparency were primary environmental factors associated with phytoplankton composition. Our study confirmed that different marine aquaculture systems can cause environmental fluctuations. Among the three systems, seaweed cultivation can bring multiple positive effects by improving surrounding water quality and increasing the phytoplankton composition. G. lemaneiformis culture in summer has great positive impact on seawater environment as it can maintain the ecological balance and reduce the risk of harmful algal blooms (HABs), and therefore, it is strongly recommended more G. lemaneiformis cultivation in this region in summer.

Diel Variation of Phytoplankton Communities in the Northern South China Sea under the Effect of Internal Solitary Waves and Its Response to Environmental Factors

Internal solitary waves (ISWs) are a common marine internal wave phenomenon in the northern South China Sea that cause significant changes in environmental factors and affect phytoplankton communities. This study investigates the short-term response of phytoplankton communities affected by ISWs based on day–night continuous sampling analysis of the sea area following the passage of an internal wave. The results revealed that, due to the IW-mediated transport of nutrients from deeper to shallower layers, the cell abundance of most small- and medium-volume phytoplankton significantly increased after the passage of ISWs. Using a method based on functional traits, we categorized phytoplankton into four functional groups. Moreover, this study revealed the differences in functional group changes in phytoplankton before and after ISWs. The abundance of mixotrophic phytoplankton in the community decreased, whereas autotrophic and heterotrophic phytoplankton increased.

Use of multivariate analysis to identify phytoplankton bioindicators of stream water quality in the monomodal equatorial agroecological zone of Cameroon.

The aquatic ecosystem is compromised by many contaminants that may reduce ecosystem functions and severely affect human health. This study aimed at determining suitable phytoplankton bioindicators of water quality for biomonitoring of freshwater streams in the monomodal agroecological zone of Cameroon. Water physicochemical and hydrological parameters, together with phytoplankton abundance and diversity, were measured from June 2016 to May 2017 along the Benoe Stream. Principal component analysis and redundancy analysis were used to determine phytoplankton spatial and temporal distribution and identify indicator species. The Shannon-Wiener diversity and Pielou's evenness indices indicated a clean to mildly polluted stream with a diverse phytoplankton community consisting of 84 genera belonging to 51 families that was dominated by the Bacillariophyta (64%), followed by Chlorophyta (13%) and Cyanophyta (10%). The total dissolved solids, electrical conductivity, stream water velocity, and discharge were the most important stream characteristics affecting the abundance of the dominant phytoplankton genera. Seasonal variations in the stream characteristics as well as spatial community distribution along an urban-small-scale farming - large-scale farming gradient were unveiled and their influence on the phytoplankton relative abundances. Increased abundance of Synedra ulna was indicative of low TDS and EC, which was the contrary for Gyrosigma baltium dominance. High Pleurosira laevis abundance was associated with the urban zone while high Diatoma sp. and Oscillatoria sp. abundances were related to the large-scale farming zone of the stream. These phytoplankton species have good potential for use as bioindicators for stream water quality monitoring in the monomodal agroecological zone.

Phytoplankton Size Structure and Diversity in the Transitional System of the Aquatina Lagoon (Southern Adriatic Sea, Mediterranean).

The Aquatina Lagoon (Southern Adriatic Sea, Mediterranean Ecoregion) is a transitional water ecosystem with great ecological and socio-economic interest. Anthropogenic activities around the lagoon (e.g., agriculture and tourism) and hydrology can affect the environmental quality and biodiversity of the lagoon. Herein, the dynamics and diversity of phytoplankton communities were studied before and after the opening of a new canal connecting the lagoon with the sea, by using different approaches based on an evaluation of the size and structure of the phytoplankton as well as the taxonomic analyses. The lagoon depicted time-related fluctuations in chemical-physical parameters. The phytoplankton trend was characterized by an increase in abundance and biomass in summer, when pico-sized autotrophs dominated. Generally, nano-sized phytoflagellates dominated the community, while micro-sized dinoflagellates and diatoms were less abundant. An increase in the phytoplankton taxa number was observed throughout the years. All the analyzed parameters were generally relatively homogeneous before the opening of the channel, while some quantitative differences among stations were observed in the second sampling period. Considering the statistical evidence, both environmental and biological parameters were affected by the "dilution" effect exerted by marine water inputs. This research supports the evidence that phytoplankton is a good indicator of the environmental status, and the obtained results contribute to the implementation of management strategies for the conservation of transitional water ecosystems.

Physical Drivers of Monthly Variation in Phytoplankton Community in the Tidal Freshwater Zone of the Macrotidal Qiantang River Estuary, Eastern China: Implications for Reducing the Risk of Harmful Cyanobacterial Blooms

AbstractThe Qiantang river estuary flows into Hangzhou Bay, on the East China Sea, and has one of the largest tidal bores worldwide. The tidal freshwater zone (TFZ) in this shallow macrotidal estuary is subjected to strong riverine and marine forcings. We investigated monthly variation of phytoplankton and environmental drivers in the upper and lower sections of TFZ during 2016. Large numbers of phytoplankton taxa (422) and genera (161) were identified. Diatoms were dominant in most months, but cyanobacteria abundance reached its greatest in warm months when runoff was low. Surprisingly, relatively high dominances of marine diatom species (e.g., Cyclotella stylorum, Skeletonema, and Thalassiosira) were observed in the TFZ with salinities usually <1 PSU. Microcystis contributed up to 50% to phytoplankton abundance in the upper TFZ in September, consistent with upstream bloom events. Abundances of phytoplankton and cyanobacteria were significantly negatively correlated with monthly runoff and sediment fluxes. Generalized additive models suggested that variation in phytoplankton abundance was largely explained by river flow, temperature and nutrients. Phytoplankton community composition varied significantly across different months and sections. Redundancy analysis indicated that temperature and flow rate explained more variation in phytoplankton community than other variables, but nutrients, Secchi depth and salinity also contributed significantly to the explained variation. Variance partitioning analysis confirmed that phytoplankton variation was largely regulated by physical variables rather than nutrients. These findings highlight the unexpectedly great phytoplankton species richness, dominance of marine diatoms, and physical drivers in the eutrophic macrotidal TFZ under strong tidal forcing.

Phytoplankton and Microzooplankton Community Structure and Assembly Mechanisms in Northwestern Pacific Ocean Estuaries with Environmental Heterogeneity and Geographic Segregation.

Phytoplankton and microzooplankton are crucial players in marine ecosystems and first responders to environmental changes, but their community structures and how they are shaped by environmental conditions have rarely been studied simultaneously. In this study, we conducted an eDNA metabarcoding sequencing combined with multiple statistical methods to simultaneously analyze the phytoplankton and microzooplankton in Liaohe (LH) and Yalujiang (YLJ) estuaries. The major objective was to examine how plankton community structure and assembly mechanism may differ between two estuaries with similar latitudinal position and climate but geographical segregation and differential level of urbanization (more in LH). Clear differences in diversity and composition of phytoplankton and microzooplankton communities between LH and YLJ estuaries were observed. Richness of phytoplankton was significantly higher in LH than YLJ, while richness of microzooplankton was higher in YLJ. The magnitude of intrahabitat variations in phytoplankton communities was significantly stronger than that of microzooplankton. Some phytoplankton and microzooplankton taxa also showed interhabitat differences in their relative abundances. Phytoplankton showed a stronger geographic distance-decay of similarity than microzooplankton, while significant environmental distance-decay of similarity in microzooplankton was found in the less urbanized YLJ estuary. Community assembly of phytoplankton was, based on the neutral community models, driven primarily by stochastic processes, while deterministic processes contributed more for microzooplankton. Furthermore, we detected wider habitat niche breadths and stronger dispersal abilities in phytoplankton than in microzooplankton. These results suggest that passive dispersal shapes the phytoplankton community whereas environmental selection shapes the microzooplankton community. IMPORTANCE Understanding the underlying mechanisms shaping a metacommunity is useful to management for improving the ecosystem function. The research presented in the manuscript mainly tried to address the effects of habitat geography and environmental conditions on the phytoplankton and microzooplankton communities, and the underlying mechanisms of community assembly in temperate estuaries. In order to achieve this purpose, we developed a metabarcoding sequencing method based on 18S rRNA gene. The phytoplankton and microzooplankton communities from two estuaries with similar latitude and climatic conditions but obvious geographical segregation and significant environmental heterogeneity were investigated. The results of our study could lay a solid foundation for ascertaining phytoplankton and microzooplankton communities in estuaries with obvious environmental heterogeneity and geographic segregation and mechanisms underlying community assembly.

Dissolved Oxygen and Water Temperature Drive Vertical Spatiotemporal Variation of Phytoplankton Community: Evidence from the Largest Diversion Water Source Area.

In order to study the vertical distribution characteristics of phytoplankton in the Danjiangkou Reservoir, the water source of the Middle Route Project of the South-North Water Diversion, seven sampling sites were set up in the Reservoir for quarterly sampling from 2017 to 2019, and water environment surveys were conducted simultaneously. The results showed that 157 species (including varieties) were identified, belonging to 9 phyla and 88 genera. In terms of species richness, Chlorophyta had the largest number of species, accounting for 39.49% of the total species. The Bacillariophyta and Cyanobacteria accounted for 28.03% and 13.38% of the total species, respectively. From the whole Danjiangkou Reservoir, the total phytoplankton abundance varied from 0.09 × 102 to 20.01 × 106 cells/L. In the vertical distribution, phytoplankton were mainly observed in the surface-thermospheric layer (I-II layer) and the bottom layer, while the Shannon-Wiener index showed a trend of gradually decreasing from the I-V layer. The Surfer model analysis showed that there was no significant stratification in the Q site's water temperature (WT) and dissolved oxygen (DO) levels in the water diversion area during the dynamic water diversion process. A canonical correspondence analysis (CCA) showed that DO, WT, pH, electrical conductivity (Cond), chemical oxygen demand (CODMn), total phosphorus (TP), ammonia nitrogen (NH4+-N), and total nitrogen (TN) had significant effects on the vertical distribution of phytoplankton (p < 0.05). A partial Mantel analysis showed that the vertical distribution of the phytoplankton community was related to WT, and the phytoplankton community structure at the other sites, except for Heijizui (H) and Langhekou (L), was affected by DO. This study has positive significance for exploring the vertical distribution characteristics of a phytoplankton community in a deep-water dynamic water diversion reservoir.

Pigment and fluorescence proxies to estimate functional diversity of phytoplankton communities

Pigment and fluorescence proxies to estimate functional diversity of phytoplankton communities

Documenting the impacts of increasing salinity in freshwater and coastal ecosystems: Introduction to the special issue

Documenting the impacts of increasing salinity in freshwater and coastal ecosystems: Introduction to the special issue

Spatio-temporal variation of phytoplankton community and its relationship with environmental factors in Danjiangkou Reservoir

Spatio-temporal variation of phytoplankton community and its relationship with environmental factors in Danjiangkou Reservoir

Niche and interspecific association with respect to the dominant phytoplankton species in different hydrological periods of Lake Wuchang, China

In aquatic ecosystems, the dynamics of ecological parameters play an important role in community organizations. To understand the seasonal variation in the phytoplankton community in Lake Wuchang, Anhui Province, water samples were collected in three different hydrological periods (dry season, normal season, and wet season) from December 2019 to August 2020. The dominance value (Y), niche width (Bi), niche overlap (Oij), variance ratio method (VR), chi-squared test (χ2), and association coefficients were used to analyze the niche and interspecific association with respect to the dominant phytoplankton species in different hydrological periods, while the redundancy analysis method (RDA) was used to distinguish the key driving environmental factors for the dominant phytoplankton species. The results showed that 308 species belonging to 8 phyla were identified, of which 13 species from 4 phyla were the dominant species. From the dry season to wet season, the dominant species changed from Bacillariophyta to Cyanophyta, while Synedra acus was the dominant species throughout the hydrological periods. The niche width of the dominant species varied from 1.77 to 6.65, and the niche width of Dinobryon was the lowest, while that of Synedra acus was the highest. The niche overlap showed temporal and spatial differences, of which 30 dominant species pairs were greater than 0.600, indicating that they occupied the environmental resources in a highly similar way. The interspecific association results showed that there was a significant positive correlation between the dominant species, especially in normal and wet seasons. Only 10 of the 48 dominant species pairs had significant associations based on the χ2 test, and two pairs had negative associations in the wet season, which might be related to the hydrological condition in the wet season. According to redundancy analysis, NO3−-N, NH4+-N, PO43--P, water depth (WD), and water temperature (WT) were the key environmental factors affecting the phytoplankton community variation in Lake Wuchang. This paper provides a new perspective for the study of the early warnings regarding the cyanobacteria bloom outbreak, and the management and protection of the water ecological environment in shallow lakes in the middle and lower reaches of the Yangtze River.

Phytoplankton Community Diversity and Its Environmental Driving Factors in the Northern South China Sea

The South China Sea (SCS) plays an important role in global marine ecology. Studies of phytoplankton diversity promote the sustainable utilization of resources in the SCS. From July to August 2020, the phytoplankton community structure at 47 stations in the northern SCS was investigated. Species composition and distribution of phytoplankton, water quality, diversity index, main influencing factors, and succession characteristics of the community structure were analyzed in combination with the survey results from previous years. A total of 332 separate taxa from 83 genera and three phyla were identified, including 142 species and 45 genera of Bacillariophyta, 188 species and 36 genera of Dinophyta, and two species and two genera of Chrysophyta. Average phytoplankton cell abundance was 649.97 cells/L. Nitzschia spp., Thalassionema nitzschioides, and Scrippsiella spp. were the dominant species. Scrippsiella spp. was found for the first time as a dominant species in the northern SCS. Meanwhile, Nitzschia spp. was associated with organic-polluted water. The high-value areas of Nitzschia spp. also indicated eutrophication, and water was slightly polluted. The Shannon–Weiner diversity index of the surface layer was 0.99–4.56 (with a mean of 3.57), and the evenness index was 0.23–0.96 (with a mean of 0.83). The phytoplankton community structure in the northern SCS was deemed to be stable. Pearson correlation analysis showed that the sum of nitrate and nitrite was significantly negatively correlated with the abundance of dinoflagellate, which indicated restrictions as a result of the sum of nitrate and nitrite, with no significant correlation between ammonium salt and various groups. Small- and medium-sized phytoplankton are usually dominant in the SCS, where nitrogen is limited.

Characteristics of Eukaryotic Phytoplankton Community Structure and Its Relationship with Environmental Factors in Danjiangkou Reservoir

Eukaryotic phytoplankton play crucial roles in ecosystem processes, and understanding their community composition and abundance is of great importance to protect the balance of aquatic ecosystems. Danjiangkou Reservoir is a canyon lake in central China that acts as the water source of the Mid-route of South-to-North Water Diversion Project. In this study, the composition of planktonic microeukaryotes from water samples with a depth ranging from 0.5 to 20 m in Danjiangkou Reservoir were investigated using high-throughput 18S rDNA gene sequencing. The environmental factors including pH, water temperature (WT), nitrate (NO3--N), ammonia (NH4+-N), total nitrogen (TN), conductivity (Cond.), water depth, and dissolved oxygen (DO) in the reservoir areas were measured, and their correlations with the abundance and diversity of eukaryotic phytoplankton were analyzed. The results of high-throughput sequencing showed that a total of 68 genera of phytoplankton belonging to 12 phyla were detected, and the phytoplankton communities were mainly composed of Dinophyceae, Bacillariophyta, and Chlorophyta. In particular, significant differences in the diversity of phytoplankton communities on a vertical distribution were found. The diversity and abundance of the phytoplankton communities in Songgang (SG), Tumen (TM), and Dangzikou (DZK) decreased with the increase in water depth, and the relationship between phytoplankton and water depth in other sampling sites was not obvious. The results of RDA showed that NO3--N, water depth, DO, pH, and WT could influence the vertical distribution of the phytoplankton community in the Danjiangkou Reservoir. Among these phytoplankton types, Dinophyceae was negatively correlated with NO3--N and water depth and positively correlated with other environmental factors. Meanwhile, Bacillariophyta was positively correlated with NO3--N and water depth and negatively correlated with other environmental factors. In addition, Chlorophyta was negatively correlated with WT, pH, and DO and not significantly correlated with water depth.