Dominant Phytoplankton Species Research Articles

Phytoplankton assemblages in response to environmental variability in tropical coastal waters of the Malacca Straits, Malaysia

AbstractSurface phytoplankton community, abundance, and species spatial distributions were investigated in the Malacca Straits (MS) of Peninsular Malaysia during the late northeast monsoon (March) and southwest monsoon (August) in 2019 to understand factors controlling their community dynamics. This study reveals that the monsoonal transitions lead to changes in sea surface temperature (SST), sea surface salinity (SSS), total nitrogen (TN), total chlorophyll‐a (Tchl‐a), and phytoplankton density in the MS. A total of 204 and 163 phytoplankton species were identified during March and August, respectively, with diatoms representing the most (80.6%), followed by dinoflagellates (9.9%), cyanobacteria (8.3%), and others (1.2%). Meanwhile, the average total phytoplankton density was lower in March (10.78 × 103 ± 14.70 cell L−1) and greater in August (26.98 × 103 ± 45.63 cell L−1), with Chaetoceros compressus and Thalassiosira sp. Seven found the highest in each season, respectively. There was no significant correlation between phytoplankton density and environmental parameters in the MS, except for the cyanobacteria and dinoflagellate communities. However, the Canonical Correspondence Analysis results showed that environmental parameters such as SST, SSS, and nutrients in the MS could affect the dominant phytoplankton species, particularly diatoms. The findings suggest that environmental changes between the seasons may act as ecological drivers in the formation of phytoplankton communities in marine habitats of the MS.

Changes in the limiting nutrients and dominant phytoplankton communities of three major European rivers: Response to catchment lithologies and human activities

Catchment lithologies and human activities can cause variations in riverine carbon (C), nitrogen (N), and phosphorus (P) loads, and the ratio of these nutrients may affect the primary productivity of rivers and their phytoplankton communities. We conducted a comparative study of biogeochemical variations in three major European rivers—the Rhine, Danube, and Seine—which reveals the impacts of different carbonate outcrops and human impacts (agricultural activities and sewage input) on the changes in the limiting nutrients and phytoplankton community compositions of flowing water systems. N limitation was observed in the Rhine and Danube owing to their low average NO3– loads (4.04–6.45 mg/L). Although the extensive outcrops of carbonate rocks in the Seine catchment result in high average HCO3– concentrations of ∼ 4.68 mmol/L, the elevated inorganic C input did not match the high average NO3– loads (∼19.38 mg/L), driven by intensive agricultural activity and urban sewage input, demonstrating a potential C limitation on productivity. Our results show that the productivity of the Seine River, determined by the chlorophyll-a concentration, was significantly related to the dissolved inorganic carbon (DIC) concentration (coefficient of determination: R2 = 0.68, P < 0.05). Our results demonstrate that changes in DIC content can significantly alter the dominant phytoplankton species in the water column. The high inputs of DIC and aqueous CO2(aq) to the Seine lead to Bacillariophyta proportions that are 3.96–8.81 % and 19.87–22.56 % higher than those of the Rhine and Danube in the wet and dry seasons, respectively. This can be explained by the difference in the efficiency of carbon concentrating mechanisms (CCMs) among phytoplankton species. Therefore, to mitigate river eutrophication and improve the quality of the aquatic environment, we suggest that future water–carbon management in the flowing water systems with abundant nutrients should consider C-limitation alleviation and its potential effect for reducing the abundance of harmful algae.

Detection of Autumnal Concentration of Coscinodiscus granii in the Southern Baltic—A Method for In Situ Measurement of Marine Particles

Efficient means for measuring the abundance and species composition of phytoplankton in situ continue to pose a big challenge to scientists. Hitherto, analyses and interpretations have been based mainly on small numbers of data acquired from microscopic examinations of water samples. Hence, information on devices facilitating such measurements is highly desirable. This paper examines the opportunities offered by the LISST-100X instrument for measuring in situ the concentrations and spatially variable biovolumes of a species dominant in the southern Baltic during the autumnal bloom. Microscopic analysis of phytoplankton in water sampled from different locations in the southern Baltic confirmed earlier results, indicating that this bloom was due to the overriding prevalence of one microplankton diatom species—Coscinodiscus granii. Combining the microscopic measurements of C. granii cell sizes with the size distribution ranges employed by the LISST-100X yielded equivalent spherical diameters (EDSs) ranging from 47.4 to 188.0 µm, with maxima in the 78.4–92.6 and 92.6–109 ranges. Comparative analysis of the particle size distribution (PSD) spectra was used to separate the abundance of C. granii from the total suspended particulate matter (SPM). Spatial in situ measurements in 2012 and 2014 of C. granii concentrations in surface waters showed that both its abundance and its percentage contribution to the total SPM were highly variable. Over a distance of several km, these concentrations varied from values close to zero to 0.2 µL L−1 in 2012 and from 0.3 to 0.9 µL L−1 in 2014, whereas the percentage in the total SPM was found to vary locally from a few to c. 50%. The proposed method and results demonstrate the success of the LISST-100X instrument in detecting size and volume concentrations of phytoplankton in size classes ranging from 1.25 to 250 μm. However, the correct interpretation of LISST data requires that the dominant phytoplankton species concentration in the suspensions be large enough for the signal (peak) to be readily visible against the background PSD of other SPM.

Hydrobiological assessment of two lakes of Jahangirnagar University campus, savar, Bangladesh

The physicochemical and biological parameters of the water in two different lakes on the Jahangirnagar University campus were evaluated between December 2018 and August 2019. The chosen metrics were air and water temperature, Secchi depth, alkalinity, conductivity, pH, total dissolved solids (TDS), dissolved oxygen (DO), soluble reactive phosphate (SRP), soluble reactive silicate (SRS), nitrate-nitrogen (NO3-N) and phytoplankton density (PD). The correlation between all the matrics was done. 37 orders of phytoplankton from lake-1 and 35 orders of phytoplankton from lake-2 were found under 8 classes (Cyanophyceae, Chlorophyceae, Bacillariophyceae, Synurophyceae, Euglenophyceae, Cryptophyceae, Dinophyceae, and Xanthophyceae). According to the principal component Analysis (PCA), 53.8% variation was found among the classes. In addition, Monoraphidium, Oscillatoria, Cosmarium, Actinastrum, Trachlelomonas, Euglena, Pediastrum, Pinnularia, and Synedra were found to be dominant species. It examined the relationships between various environmental factors and dominant phytoplankton species in two lakes and found that the effects of the physicochemical parameters differ depending on the lake and dominant phytoplankton type. The study found negative correlations between various water quality parameters and phytoplankton taxa, suggesting an influence of environmental conditions on phytoplankton communities. Bangladesh J. Bot. 53(1): 159-171, 2024 (March)

Enhancing water quality and ecosystems of reclaimed water-replenished river: A case study of Dongsha River, Beijing, China

The use of reclaimed water for urban river replenishment has raised concerns regarding its impact on water quality and aquatic ecosystems. This study aims to reveal the improvements seen in an urban river undergoing a practical water eco-remediation after being replenished with reclaimed water. A one-year monitoring of water quality, phytoplankton, and zooplankton was carried out in Dongsha River undergoing eco-remediation in Beijing, China. The results showed that compared to the unrestored river, the concentrations of COD, NH4+-N, TP, and TN decreased by 28.22 ± 7.88 %, 40.24 ± 11.77 %, 44.17 ± 17.29 %, and 28.66 ± 10.39 % in the restoration project area, respectively. The concentration of Chlorophyll-a in the restoration area was maintained below 40 μg/L. During summer, when algal growth is vigorous, the density of Cyanophyta in the unrestored river decreased from 46.84 × 104cells/L to 16.32 × 104cells/L in the restored area, while that of Chlorophyta decreased from 41.61 × 104cells/L to 11.87 × 104cells/L, a reduction of 65.16 % and 71.47 %, respectively. The dominant phytoplankton species were replaced with Bacillariophyta, such as Synedra sp. and Nitzschia sp., indicating that the restoration of aquatic plants reduces the risk of Cyanophyta blooms. Zooplankton species also changed in the restoration area, especially during summer. The density of pollution-tolerant Rotifer and Protozoa decreased by 31.06 % and 27.22 %, while the density of clean water indicating Cladocera increased by 101.19 %. We further calculated the diversity and evenness index of phytoplankton and zooplankton within and outside the restoration area. The results showed that the Shannon-Weaver index for phytoplankton and zooplankton in the restoration area was 2.1 and 1.91, which was higher than those in the river (1.84 and 1.82). This further confirmed that aquatic plant restoration has positive effects. This study can provide a practical reference and theoretical basis for the implementation of water ecological restoration projects in other reclaimed water rivers in China.

Distribution and dynamics of niche and interspecific association of dominant phytoplankton species in the Feiyun River basin, Zhejiang, China

Distribution and dynamics of niche and interspecific association of dominant phytoplankton species in the Feiyun River basin, Zhejiang, China

Unveiling the evolution of phytoplankton communities: Decades-long insights into the southern Yellow Sea, China (1959–2023)

We obtained historical and observational data on phytoplankton communities from 1959 to 2023 to explore the responses of the phytoplankton community structure to long-term environmental changes in the southern Yellow Sea (SYS), China. The results revealed a decrease in the proportions of diatom cell abundance within the phytoplankton community by 8 %, accompanied by a corresponding increase in that of dinoflagellates. Dominant phytoplankton species were mainly chain-forming diatoms before 2000, and large dinoflagellate species from the genera Tripos and Noctiluca increased their dominance after 2000. Warm-water phytoplankton species have increased in dominance over the study period. Correlation analysis revealed that the ocean warming and alterations in nutrient structure (N/P and Si/N ratios) were mostly responsible for the long-term evolution trend, and these changes may result in an increase in dinoflagellate harmful algal blooms, reduced efficiency of the biological carbon pump, and heightened hypoxia in the future, which should draw our attention.

Phytoplankton Dynamics and Biogeochemistry: Model Studies

The seasonal dynamics of the NE Black Sea phytoplankton follow the following pattern: small diatoms (spring) → coccolithophorid Emiliania huxleyi (late spring–early summer) → large diatoms (summer). Our hypothesis states that nitrogen and phosphorus concentrations regulate the seasonal phytoplankton dynamics. A minimum number of parameters is enough to understand the mechanisms of dominant species change. Based on the concept of intracellular regulation, the following parameters were evaluated: the minimum nitrogen and phosphorus quotas; half-saturation constants for nitrogen and phosphorus uptake; the maximum specific growth rate of the dominant phytoplankton species. Computational experiments on the model show the following: (1) in spring, a species with a high maximum specific growth rate becomes dominant; (2) in late spring and early summer, a species with a low minimum nitrogen quota and a low half-saturation constant for nitrogen uptake is observed; (3) in summer, a low minimum phosphorus quota and a low half-saturation constant for phosphorus uptake allow the species to become dominant.

Spatial heterogeneity in summer phytoplankton communities shaped by anthropogenic and natural effects in typical coastal bay-river systems in South China

Phytoplankton community spatial scales vary in typical coastal bay-river systems under natural and anthropogenic effects. However, their relative importance in shaping phytoplankton spatial heterogeneity has been largely uncharacterized in the literature. In this study, we performed comprehensive analyses using field monitoring, meteorological, and remote sensing datasets from a coastal bay-river system in South China (the Guangdong-Hong Kong-Macao Greater Bay-Pearl River tributaries) to examine phytoplankton spatial heterogeneity and main effects. We showed that water quality in the four water bodies of the typical coastal bay-river system in South China were relatively poor. Phytoplankton community abundance, taxonomic grouping, dominant species, and species similarity varied significantly in response to environmental gradients. We showed that Cyanophyta, Bacillatiophyta, and Chlorophyta were dominant phyla, and we observed regional variations in taxonomic groups and dominant species. Phytoplankton abundance was significantly higher in Dongjiang River and water bodies in branched bays when compared with other regions due to nutrient input from extensive agricultural and urban development, where the dominant phylum was Cyanophyta. Cyclotella (Bacillariophyta) had relatively high abundance and was widely distributed throughout the coastal bay-river system, except in the Dongjiang River. Melosira (Bacillariophyta) had relatively high abundance in Dongjiang and Xijiang Rivers, Merismopedia (Cyanophyta) dominated in the Dongjiang River and highly urbanized branched bay areas, while Microcystis (Cyanophyta) only dominated in Beijiang and Xijiang Rivers. Dominant species distributions showed apparent spatial heterogeneity in phytoplankton community composition. Species similarities between different water bodies were generally low, but phytoplankton species similarities between the Dongjiang River and water bodies in the branched bay area were relatively high, which indicated that water exchange associated with freshwater and nutrient inputs may have profoundly influenced species dispersal and dominant phytoplankton species. Redundancy analyses (RDA) demonstrated that pH, elevation, photosynthetically active radiation (PAR), dissolved active phosphorus (SRP), total dissolved phosphorus (TP), total nitrogen (TN), and nitrate nitrogen (NO3−-N) values - associated with nutrient and climate indicators were the main factors explaining structured phytoplankton spatial distributions. Variance partitioning analyses (VPA) showed that phytoplankton community variations were explained by anthropogenic factors (eutrophication) in summer. Our study improves our understanding of the natural and anthropogenic effects on phytoplankton spatial heterogeneity and provides basic study data for long-term phytoplankton evolution from river to bay areas.

Ecological importance of rare phytoplankton species revealed by their high contribution to unsaturated fatty acids in tropical waters

Abstract There is increasing evidence that rare species play an important role in trophic interactions, but the function of rare species with low biomass in these processes remains unclear. Phytoplankton is placed at the base of lentic and marine food webs and is characterised by a few dominant species and many rare species. While the dominant species contribute most to the primary production, they are often low‐quality food for primary consumers. The rare species may instead provide the essential biochemical nutrients for consumers, especially in eutrophic waters. We hypothesised that the biomass of rare eukaryotic phytoplankton species significantly determines the concentrations of sestonic long‐chain highly unsaturated fatty acids, directly linking them to the functioning of aquatic ecosystems. We applied redundancy analysis and Lasso regression models to identify the species whose population dynamics explain the variations of sestonic fatty acids concentrations in tropical reservoirs and lakes. The lasso models predicted that the dominant phytoplankton species determined the concentration of saturated sestonic fatty acids and that rare phytoplankton species were the main determinant for polyunsaturated fatty acids, which are critical for the food quality of consumers such as zooplankton and promote the energy transfer from primary producers to higher trophic levels in natural waters. In particular, the biomass of the rare species Scenedesmus obliquus was a key variable explaining the variations of α‐linolenic acid, α‐linoleic acid, γ‐linolenic acid, and eicosapentaenoic acid concentrations. We conclude that the population dynamics of rare phytoplankton species can define the food quality associated with eicosapentaenoic acid for consumers and thus play a critical role in the trophic transfer in the food webs of tropical waterbodies.

The molecular mechanisms and environmental effects of modified clay control algal blooms in aquacultural water

Modified clay (MC) technology is an effective method for controlling harmful algal blooms (HABs). Based on field experience, a bloom does not continue after treatment with MC, even though the residual HAB biomass accounts for 20–30% of the initial biomass. Laboratory studies using unialgal cultures have found that MC could inhibit the growth of the residual algal cells to prevent HABs. Nevertheless, the phytoplankton in field waters is diverse. Therefore, unclassified complex mechanisms may exist. To illustrate the molecular mechanisms through which MC controls HABs in the field and verify the previous laboratory findings, a series of experiments and bioinformatics analyses were conducted using bloom waters from aquacultural ponds. The results showed that a 72.29% removal efficiency of algal biomass could effectively control blooms. The metatranscriptomic results revealed that the number of downregulated genes (131,546) was greater than that of upregulated genes (24,318) at 3 h after MC addition. Among these genes, several genes related to DNA replication were downregulated; however, genes involved in DNA repair were upregulated. Metabolism-related pathways were the most significantly upregulated (q < 0.05), including photosynthesis and oxidative phosphorylation. The results also showed that MC reduced most of the biomass of the dominant phytoplankton species, likely by removing apical dominance, which increased the diversity and stability of the phytoplankton community. In addition to reducing the pathogenic bacterial density, MC reduced the concentrations of PO43− (96.22%) and SiO32− (66.77%), thus improving the aquaculture water quality, altering the phytoplankton community structure (the proportion of Diatomea decreased, and that of Chlorophyta increased), and inhibiting phytoplankton growth. These effects hindered the rapid development of large phytoplankton biomasses and allowed the community structure to remain stable, reducing HAB threats. This study illustrates the molecular mechanisms through which MC controls HABs in the field and provides a scientific method for removing HABs in aquacultural waters.

The Impacts of Land Use and Seasonal Effects on Phytoplankton Taxa and Physical-Chemical Variables in the Tigris River within the City of Mosul

We investigated the effect of land use based on the dominant phytoplankton and physical-chemical variables in the different areas of the Tigris River, within the city of Mosul. Agricultural and urban activities have a significant impact on the water quality of the river. Regardless of physical and chemical variables, phytoplankton act as a bio-indicator of water quality due to their fast and sensitive response to changes in the environment. Our research was conducted in the Tigris River within the city of Mosul by examining the phytoplankton species and the physical-chemical variables at 16 sites during each vegetation period. Point and non-point source pollutants have affected the Tigris River within the city of Mosul, getting into the river from upstream through agricultural activities and by urban activities in the middle section of the city, respectively from both banks. Based on our results, we observed the highest phytoplankton abundance during the October sampling periods, while the lowest occurred during the July sampling period, which was associated with maximum water temperature and absence of rain. According to our study, land use (e.g., agricultural, and urban activities) greatly affected the dominant phytoplankton species and physical-chemical variables of the Tigris River. Oscillatoria sp. dominated all seasons in the agricultural region, while at the same time, we observed an increase in the number of phytoplankton species caused by the nutrient availability upstream on the river. The effects of climate have very significant and characteristic effects in this area, which basically determine the community of organisms and the water quality; the effects resulting from anthropogenic activity significantly modify this. Based on our investigation, in the part of the Tigris River connected to Mosul, we found a clear connection between the pollution caused and the effects of different land uses, through the examination of the algal community and physical-chemical variables in different periods of the year.

Relationship between phytoplankton distribution and salinity in the giant artificial brackish Lake Saemangeum

In 2021, an abundance of phytoplankton species was observed in Lake Saemangeum. We analyzed the relationship between phytoplankton abundance and salinity by comparing the distribution of salinity that changed because of freshwater inflow and drainage sluice gate operation. Thirteen field surveys were conducted: monthly basic surveys from January to November 2021 and additional surveys after rainfall in August and September at seven sites. During the survey period, 46–94 species were recorded. Pearson correlation coefficients were used to analyze the relationship between salinity and abundance of the dominant phytoplankton species. The result showed that Cyclotella atomus, Stephanodiscus hantzschii, Phormidium tenue, and Chaetoceros spp. were correlated with salinity. Chaetoceros spp. was significantly positively correlated (p < 0.001), whereas all other species were negatively correlated. Moreover, the correlation coefficient between seven species and salinity was close to zero. Compared with the general correlation coefficient of salinity and abundance, the point-biserial correlation coefficient showed a higher overall absolute value. Four species (Skeletonema spp., Cyclotella atomus, Phormidium tenue, Chaetoceros spp.) exhibited p < 0.001. Particularly, the correlation coefficient of Cyclotella atomus changed significantly from -0.237 to -0.451, whereas that of Phormidium tenue changed from -0.207 to -0.431. The results imply that salinity can affect the distribution and survival of euryhaline species. Therefore, high salinity may inhibit some freshwater and euryhaline species in the lake. However, further research is required to validate our findings.

Advances in phytoplankton population ecology in the Pearl river estuary

Phytoplankton is an important primary producer of the estuarine ecosystem, which is essential for the biogeochemical cycle of water elements and nutrient transfer. The Pearl River estuary (PRE) is a dynamically complex estuary, and the environment of PRE is significantly impacted by anthropogenic activities, variation of phytoplankton community structure in the PRE are complex. This review aims to compare phytoplankton species, species diversity, and abundance variation characteristics from the 1980s and 2020s, evaluate the overall trend of phytoplankton in the PRE, and discuss the main environmental factors affecting phytoplankton growth in the PRE. The data from the past 40 years in PRE showed that the number of phytoplankton species significantly decreased (p &amp;lt; 0.05). There was no significant difference in the abundance of phytoplankton at the 10-year scale, however, the fluctuation range of the abundance has increased. Under the conditions of a decreasing species number and no significant difference in abundance, the species diversity of phytoplankton showed a downward trend. In addition, the dominant phytoplankton species in the nearshore waters were relatively homogenous, and the abundance of phytoplankton in the nearshore waters was higher than that in the open waters, which suggested that human activities have a great influence. This review can form the basis for facilitating health management in the PRE ecosystem. Further, relevant guidelines can be developed and implemented for promoting the ecological health of the Guangdong-Hong Kong-Macao Greater Bay Area and ensuring its sustainable development.

Spatio-temporal patterns of phytoplankton communities and their driving environmental factors in Lake Qinghai

为了解青海湖浮游植物群落结构特征、时空分布格局及其关键环境驱动因子,于2020年5月(春)、8月(夏)、10月(秋)对青海湖进行系统调查,分析浮游植物群落在3个季度和4个区域(湖滨带、进水区、浅水区和深水区)间的差异。3次调查共检出浮游植物6门39属65种,物种组成以硅藻(36种,占总物种数的55.38%)、绿藻(17种,26.15%)和蓝藻(7种,10.76%)为主。4个区域间的浮游植物丰度存在显著差别,其中深水区丰度显著高于其他区域,主要原因可能在于深水区的环境较为稳定。3个季节间,浮游植物丰度和生物量具有较大差异:夏季和秋季的丰度、生物量均为春季的近10倍;浮游植物的优势类群和种类也发生了较大的变化:春季最具优势类群为硅藻门,优势种也主要隶属于硅藻门,而夏、秋两季则以蓝藻门种属占据主要优势。春季浮游植物的Pielou均匀度和Simpson多样性指数显著高于夏、秋两季,秋季Margalef指数和Shannon-Wiener多样性指数高于夏季。PERMANOVA分析和NMDS分析显示,青海湖浮游植物群落结构在不同区域和不同季节间具有显著差异。此外,dbRDA分析表明:盐度、水温和总磷是影响青海湖浮游植物分布的关键环境因子。与历史调查结果相比,青海湖浮游植物丰度出现数量级程度的上升,主要优势类群由硅藻门逐渐演变为蓝藻门。本研究揭示了青海湖浮游植物群落的时空分布特征及驱动因素,可为后续青海湖保护和管理提供理论支撑。;To understand the spatio-temporal of phytoplankton communities and their key environmental drivers in the Lake Qinghai, we conducted a systematic survey during May (Spring), August (Summer), and October (Autumn) in 2020, and examined how phytoplankton communities varied among three seasons and four regions (lakeshore zone, inlet zone, shallow zone, and deep zone). A total of 65 species belonging to 39 genera and 6 phyla were identified, with Bacillariophyta (36 species, accounting for 55.38% of the total species) being the species-richest class, followed by Chlorophyta (17 species, 26.15%), and Cyanophyta (7 species, 10.76%). The abundance of phytoplankton differed significantly among four regions, with significantly higher values in deep zone than other zones, probably due to the more stable environment in deep zone. There were also significant differences in abundance and biomass of phytoplankton among the three seasons. The abundance and biomass of phytoplankton in summer and autumn were nearly 10 times higher than those in spring, and the dominant groups and species of phytoplankton also changed greatly. The most dominant class in Spring was Bacillariophyta, and the dominant species were also belonged to Bacillariophyta, while the dominant group and species in Summer and Autumn became Cyanophyta and its subset species. The Pielou's evenness and Simpson diversity indices of phytoplankton in Spring were significantly higher than those in Summer and Autumn, and the Margalef and Shannon-Wiener indices showed higher values in Autumn than in Summer. PERMANOVA and NMDS both indicated that the structure of phytoplankton communities varied significantly among different regions and seasons in the Lake Qinghai. In addition, the dbRDA analysis showed that salinity, water temperature and total phosphorus were the key environmental factors affecting the phytoplankton patterns in the Lake Qinghai. Compared with the historical surveys, this study indicated that the main dominant groups of phytoplankton community in Lake Qinghai gradually changed from Bacillariophyta to Cyanophyta. This study reveals the spatio-temporal pattern and key driving factors of phytoplankton communities in the Lake Qinghai, which can provide theoretical support for the subsequent protection and management of the Lake Qinghai.

Dynamic analysis of niche and interspecific association of dominant phytoplankton species in Xiashan Reservoir

Dynamic analysis of niche and interspecific association of dominant phytoplankton species in Xiashan Reservoir

Assessing spatio-temporal dynamics of phytoplankton assemblage and ecohydrological interaction in a community managed reservoir using GIS for sustainable fisheries management

The present study assessed the spatio-temporal dynamics of phytoplankton community structure and diversity using GIS platform, and their ecohydrological interactionsof a tropical reservoir located in Eastern India. Altogether, 74 species of phytoplankton belonging to 54 genera under seven taxonomic algal groups were recorded whose average annual abundance was 74.11 × 104 ± 17.73 × 104 cells l−1. Among seven algal groups, Chlorophyta, Cyanophyta, Bacillariophyta and Euglenophyta were remarkably influencing the total phytoplankton population contributing 97% of the total phytoplankton population in the reservoir. Cyanophyta absolutely dominated in the total phytoplankton compositions, and contributed a major share of 54% at the annual average level, however the species richness was maximum under the group Chlorophyta (35 genera). In total, thirteen phytoplankton taxa emerged as dominant (γ = < 0.02) across seasons. Among them, Phormidium sp. solely contributed (16.16%) to the total phytoplankton population, marked as dominant one in the reservoir. The diversity indices indicated the greater phytoplankton diversity in the lotic zone as compared to the transitional and lacustrine zone, showing significant variations (p<0.05) across seasons. PERMANOVA analysis exhibited a significant temporal variations of phytoplankton abundance (F=1.15, p=0.02) as well asenvironmental variables (F=1.82, p<0.05), but no significant spatial variations were recorded. The Principal Component analysis (PCA) revealed water temperature, transparency, total hardness, pH, specific conductivity, total alkalinity and nutrients parameters viz., phosphate, nitrate and silicate were the most important abiotic factors having the significant influence on the phytoplankton community compositions. Canonical Correspondence Analysis (CCA) depicted the environmental factors such as temperature, total alkalinity, total hardness, transparency, pH, and nutrients (NO3-N, PO4-P and SIO4-Si) were the determinants for the distribution of overall phytoplankton population especially the dominant phytoplankton species of the reservoir. The findings provide a better understanding of the influence of ecohydrology on phytoplankton community of a community managed reservoir and also discuss management and researchable issues considering the feeding guild of reservoir fishes and phytoplankton assemblage for ecosystem based conservation and management.

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.

O2 and CO2 Responses of the Synaptic Period to Under-Ice Phytoplankton Bloom in the Eutrophic Razdolnaya River Estuary of Amur Bay, the Sea of Japan

Hydrological conditions are an important factor for aquatic ecosystems. Their contribution to stimulating phytoplankton bloom in eutrophic estuaries is not quite clear. We present the results of an outbreak of a phytoplankton bloom event observed in the eutrophic Razdolnaya R. estuary in 2022 from January 22 to February 23, when the estuary was covered by ice. The bloom spreads over 21 km from the river mouth bar to upstream in the near-bottom layer below the halocline. The Chl-a concentration in the bloom area increased from 15 to 100 μg/L, and the dissolved oxygen concentration from 350 to 567 μmol/kg at a rate of 11 μmol/(kg day) over the study period, while the CO2 partial pressure was reduced to 108 µatm in the most oxygen-supersaturated waters. The Thalassiosira nordenskioeldii Cleve sea diatom was the dominant phytoplankton species in the bloom area. The opposite trend was observed near the boundary of the saline water wedge penetration over 29 km from the river mouth bar to upstream where the dissolved oxygen concentration decreased from 140 to 53 μmol/kg over a month, and partial pressure of CO2 reached 4454 μatm. We also present the results obtained in February 2016 before and after a snowfall, when the ability of PAR to penetrate through the ice was impeded by a layer of snow. After the snowfall, photosynthesis in the under-ice water stopped and the oxygen concentration decreased to almost zero due to the microbiological destruction of the phytoplankton biomass. As such, the main effect of phytoplankton bloom is the formation of superoxia/hypoxia (depending on the light conditions), during the period of maximum ice thickness and minimum river discharge. Thus, this study demonstrates that the eutrophication in the future could lead to unstable ecosystems and large synoptic variations of dissolved oxygen and CO2 partial pressure of the estuaries.

Potential risk from and prevention of phytoplankton outbreaks in blocking the cooling water system in a nuclear power plant on the Southeast China coast

The invasion or aggregation of marine biota in coastal waters has become a common problem, threatening the safety of cooling water systems in the context of environmental and climate changes. However, studies on issues of coastal nuclear power plants from the view of marine ecology have mostly focused on the thermal effluent, entrainment effect on organisms, residual chlorine, radioactivity, etc. There is a lack of information on the safety of cooling water systems in nuclear power plants blocked by marine biota. Based on field and historical datasets, this study screened phytoplankton species that may potentially block the cooling water system of the Fuqing nuclear power plant on the Southeast China coast, identified the phytoplankton risk and a risk calendar, and established a catalog of risk phytoplankton species for the cooling water system. The screening criteria were simultaneously required as follows: (1) particle size of cells or group &amp;gt;2000 μm; (2) phytoplankton bloom or aggregation events occurred in surrounding areas; (3) and species abundance maintained at &amp;gt;0.5×105 cells/L in the surrounding area. Nine high-risk species were screened out that can easily form colonies, clusters, and groups, including Thalassiosira diporocyclus, Thalassiosira subtilis, Noctiluca scintillans, Phaeocystis globosa, Pseudo-nitzschia pungens, Pseudo-nitzschia delicatissima, Skeletonema costatum, Skeletonema dohrnii, Paralia sulcata. Due to small cells or the formation of short chains, some dominant phytoplankton species, even those with advantages in abundance and occurrence, had difficulty threatening the reliability of cooling water systems in nuclear power plants. The outbreak of different phytoplankton species varied daily, and the risk of blockage was highest from April to July. The biological characteristics, ecological mechanisms underlying outbreaks of high-risk phytoplankton species are reviewed and discussed, suggesting a high degree of temporal and spatial variability of blockage risk. Finally, main prevention and control measures used against high-risk phytoplankton species are provided to imply new ideas and methods for nuclear power plants. These strategies have very important practical and scientific significance.