Phytoplankton Abundance Research Articles

Succession Characteristics and Influencing Factors of Phytoplankton Communities in Qionghai Lake

The phytoplankton population of Qionghai Lake was surveyed in December 2015, March 2016, June 2016, September 2016, and March 2017. A total of 196 species (including varieties) belonging to 77 genera of 7 phyla were identified. The phytoplankton communities were dominated by Chlorophyta and diatoms, and there were significant differences across the five sampling sites. The phytoplankton abundance, which ranged between 13.85 × 104 and 335.54 × 104 cells·L−1, was significantly higher in spring and summer than in autumn and winter. Chlorella sp. and Cyclotella sp. were the dominant populations, and their dominance degree reached as high as 0.54 and 0.33, respectively. The diversity of the phytoplankton populations was significantly higher in spring and summer than in autumn and winter, and the Shannon–Wiener index and Margalef index ranged from 2.49–3.65 and 2.47–3.10, respectively. The water quality of Qionghai Lake was generally good. The trophic level index was between 30 and 60, showing that the water body was overall in a mesotrophic to slightly eutrophic state. The Spearman correlation analyses revealed that ammonium nitrogen (NH4+-N), water temperature (WT), permanganate index (CODMn), and transparency (SD) were the most important environmental factors that influenced the phytoplankton communities. For example, NH4+-N was significantly correlated with Chroococcus sp. (r = 0.41, p < 0.05) and Cryptomonas ovata Ehrenberg (r = 0.45, p < 0.05), and WT was significantly correlated with Cryptomonas marssonii Skuja (r = 0.43, p < 0.05) and Cryptomonas ovata (r = 0.53, p < 0.01).

Seasonal Dynamics of Phytoplankton in Integrated Paddy-cum-Fish Culture

Background: An experimental study was conducted during June-November 2020 at Tungjoy village of Manipur, India, to assess the assemblage pattern, abundance and seasonal dynamics of phytoplankton in simultaneously integrated paddy-cum-fish culture (IPFC). Methods: The experimental IPFC fields were prepared by enhancing width and height of dykes and constructing central refuge pond. Rice saplings were manually transplanted into the prepared fields in June 2020 while the common carp fingerlings were introduced 30 days after rice-transplantation. Both rice and fish were harvested in November 2020. Assemblage pattern, abundance and dynamics of phytoplankton, soil nutrients and water quality were analysed for three seasons (monsoon, post-monsoon and winter) in paddy fields without fish (PF) compared with IPFC fields. Relevant fish growth parameters were analysed on monthly basis. Result: The study recorded 37 genera of phytoplankton belonging to 25 families and 18 orders falling under class Bacillariophyceae, Chlorophyceae and Cyanophyceae. Bacillariophyceae was the most diverse class. Phytoplankton density ranges from 14.00±1.57 × 103 to 33.25±3.60 × 103 µL-1 and 9.05±2.27 × 103 to 33.06±3.45 × 103 µL-1 in PF and IPFC, respectively, wherein Chlorophyceae dominated during monsoon and post-monsoon. Phytoplankton in IPFC was lower than PF, indicating effective utilisation by the reared fish. Fish production from IPFC fields was 326 kg ha-1 with 83% survival rate while rice production was enhanced by 7.4% as compared to rice monoculture.

Physiological and interspecific factors determine diel changes in phytoplankton bio‐optical properties

AbstractBio‐optical properties of marine phytoplankton retrieved through satellite remote sensing are used to estimate ocean productivity and carbon cycling. Daily activity of phytoplankton is attuned to the predictable light fluctuations of the diel cycle. Field and laboratory studies have documented diel changes in phytoplankton growth, division, and respiration, carbon and pigment content, cell size, photosynthetic efficiency and rate, and DNA replication and transcription. Many of these physiological changes can alter cellular optical properties and contribute to diel variations in bulk absorption and scattering properties. Consequently, understanding phytoplankton contributions to diel optical cycles is essential for improving algorithms that convert remote sensing data to biological rates and stocks. Here, we describe time‐resolved cellular, photophysiological, and bio‐optical properties for three cultured phytoplankton ranging in cell size from ~ 1 to 6 μm: Ostreococcus lucimarinus, Synechococcus (WH8102), and Thalassiosira pseudonana, all of which can significantly contribute to phytoplankton abundance and/or biomass in the open and coastal ocean. This work is the first to characterize complete diel cycles in absorption and attenuation for O. lucimarinus and backscattering for all these species. Results show that the percent increase from the minimum to maximum values over the diel cycle ranged between ~ 24–121%, ~ 31–235%, and ~ 25–198% for particulate absorption, attenuation, and backscattering, respectively. Diel changes in bio‐optical properties also differed in both timing and magnitude across phytoplankton species, demonstrating the importance of contextualizing remote sensing observations with phytoplankton community composition.

The dynamic changes in phytoplankton and environmental factors within Dongping Lake (China) before and after the South-to-North Water Diversion Project

Dongping Lake is one of the most important regulation and storage lakes along the eastern route of the South-to-North Water Diversion Project in China, the water quality condition of which directly influences the safety of water diverting, because it serves as a Yangtze River water redistribution control point. However, the changes in algae, and in environmental factors affecting their community structures, before and after the water diversion project are rarely reported. In this study, the temporal variations of phytoplankton abundance were examined based on monthly samples collected at three stations from May 2010 to April 2022. The total abundance of algae greatly decreased after the water diversion project was implemented, with a relatively stable biodiversity and evenness before and after the water translocation. Multiple statistical methods were used together with the water quality indices (WQIs) and the nutrient status index (TSIM) to evaluate overall water condition and analyse relationships among environmental factors. The WQIs demonstrated a general “Good” water quality with a seasonal differentiation, and that water conditions during water transfer periods were better than during non-water transfer periods, which may be ascribed to the improved hydraulic conditions and purified water environment during water transfer periods. Redundancy analysis showed that water temperature, ammonia nitrogen, water transparency, and total phosphorus were the most important environmental factors, with relatively decreased contribution rates towards phytoplankton communities after the water translocation. Importantly, some dominant phytoplankton genera of Chlorophyta, Bacillariophyceae, and Cyanophyceae were similarly affected by water transparency, and nitrogen and phosphorus nutrients in summer after the water translocation. These research findings helped us gain a comprehensive understanding of the changing patterns of water quality and microalgae and their relationships before and after the water diversion project, providing a guidance for future lake management in regulating hydraulic conditions and improving water quality of Dongping Lake.

Effects of herbivorous fish on shallow lake ecosystems increase at moderate nutrient conditions

Submerged macrophytes are vital in shallow lakes, as they provide critical ecosystem functions and services and can stabilize the clear-water conditions by various mechanisms. Nutrient enrichment reduces the resilience of macrophyte dominance in shallow lakes, thereby making them susceptible to shifts towards phytoplankton dominance following perturbations. Here, we conducted a mesocosm experiment to examine the individual and combined effects of nutrient enrichment and the addition of grass carp (Ctenopharyngodon idella) on the abundance of submerged macrophytes, epiphyton, and phytoplankton. We hypothesized that moderate nutrient enrichment facilitates macrophyte abundance, but also phytoplankton abundance after macrophyte removal by herbivorous fish. Our data showed that herbivory by grass carp could trigger a shift from macrophytes to algal dominance in mesocosms with moderate nutrient concentrations, but not in those with low nutrient concentrations. Moderate nutrient enrichment alone promoted submerged macrophyte growth, whereas the introduction of grass carp induced a collapse of submerged macrophytes regardless of nutrient conditions. Moreover, the introduction of grass carp showed more negative effects on light conditions of the water column in mesocosms with moderate nutrient concentrations compared to those with low nutrient concentrations. A recovery of submerged macrophytes might thus be limited by low light availability in lakes with moderate nutrient conditions suffering grass carp perturbation. Our results suggest that submerged macrophyte-dominated shallow lakes with moderate nutrient conditions are vulnerable to perturbation by herbivorous fish such as grass carp. In turn, managing the abundance of herbivores in these lakes can support the dominance of macrophytes and associated clear water conditions.

Comparative analysis of organelle genomes provides conflicting evidence between morphological similarity and phylogenetic relationship in diatoms

Diatoms (Bacillariophyta) are abundant phytoplankton groups in marine environments, which contribute approximately 20% of global carbon fixation through photosynthesis. Moreover, diatoms exhibit the highest species diversity (approximately 18,000 diatom species) among marine photosynthetic eukaryotes, which were identified by morphological characteristics. Molecular phylogenetic analyses could shed new insights into the evolutionary relationships of diverse diatom species. Nevertheless, a comprehensive understanding of the phylogenetic relationships of diatom species still remains unclear because the available molecular data are insufficient compared with their high species diversity. Furthermore, several novel diatom species were reported from field samples with no molecular evidence. In particular, the phylogenies of diatom species constructed using organelle genomes revealed that several diatom genera are paraphyletic with high supporting values. We constructed high-resolution phylogenetic trees of diatom species using organelle genomes (plastids and mitochondria) and compared the morphologies in several paraphyletic diatom genera. Especially, the clades Nitzschia and Thalassiosira include several different diatom genera with high phylogenetic supports. Our study demonstrated that some morphological characteristics (e.g., genus characters) of several diatom genera could not represent current genus boundaries. Based on the results, we highlight the necessity for taxonomic reinvestigation. To reestablish this in diatoms, it will be essential to incorporate more genome data from a broader range of taxon samples, along with a comparison of morphological characteristics.

Reproductive biologies of Psammogobius knysnaensis and Caffrogobius gilchristi in a warm-temperate South African estuary

Reproductive biologies (spawning period, length at maturity and fecundity) of the Knysna sand goby Psammogobius knysnaensis and the Prison goby Caffrogobius gilchristi were investigated between September 2018 and August 2019 in the warm-temperate Sundays Estuary, South Africa. The two species reproduced during the same period (spring and summer) with peak reproduction occurring in January. P. knysnaensis egg production was higher than C. gilchristi and was not affected by fish size. Although C. gilchristi egg production increased with fish size, this was not significant. P. knysnaensis reached LM50 at smaller sizes than C. gilchristi. Reproductive periods were likely coupled with prey availability, as phytoplankton and zooplankton abundances are highest in warm-temperate estuaries during this period. The ability of these gobies to reproduce at small sizes (< 40 mm TL), which is an adaptive trait of many r-selected species, underpins their high abundance in South African estuaries as they are well adapted to stochastic environments.

Evaluation of phytoplankton abundance and wastewater quality in intensive vannamei shrimp ponds in the northern coastal area of Bangka Island

Abstract Effluent waste generated from the intensive production of vannamei shrimp is known to play an essential role in increasing phytoplankton abundance and the alteration of environmental quality. This alteration is characterized by the presence of various organic compounds and their derivatives. The northern coastal area of Bangka Island represents a region in Indonesia that has witnessed significant growth and development as a vannamei shrimp cultivation zone. Therefore, this study aims to evaluate phytoplankton abundance and environmental quality in the waste of shrimp ponds in the northern coastal area of Bangka Island. The investigation procedures were carried out in four specific locations within this area, namely BL1, BL2, BL3, and BL4. The results showed the presence of five–six distinct phytoplankton groups, including a total of 11–18 genera, within the effluent discharge from these ponds. The highest abundance of phytoplankton was recorded at BL3, with a value of 2,418,375 cells ml−1. The phytoplankton groups identified at all locations included Chlorophyta, Cyanophyta, Chryptophyta, Bacillariophyta, and Pyrrophyta. Euglenophyta was found at BL1 and BL3 but was not observed at BL2 and BL4. Furthermore, the most abundant group found in this study was Chlorophyta. The genera Nanochloropsis, Chlorella, Microcystis, and Nitzschia were consistently found in all the surveyed ponds. The calculation results showed that all locations had a moderate level of diversity, high evenness, and the absence of dominance. Based on the findings of principal component analysis, there was a commonality in parameters that exerted a strong influence on phytoplankton abundance, including nitrate, orthophosphate, and magnesium.

The study of phytoplankton in the Banggai Deep Sea: The study case of Banggai Upwelling Dynamics and Ecosystem Experiment (BUDEE)

The upwelling process in the Banggai deep-sea water occurs yearly during the east monsoon. The upwelling process is characterized by low surface water temperatures compared to the surrounding waters, high nutrient values of phosphate, nitrate, and silicate, and high values of primary productivity. The aim of this research was to determine the types of phytoplankton that are abundant in the Banggai deep-sea waters during the upwelling process. Phytoplankton sampling was conducted at 36 stations using a phytoplankton net from a depth of 150 m to the water surface. The mesh size of the phytoplankton net was 80 µm with a net length of 100 cm. Phytoplankton samples were preserved using 4% formalin. Based on the research results, the highest total abundance of phytoplankton was found at station 13 (315.457 cells.m-3), followed by stations 20 (234.746 cells.m-3), 26 (213.865 cells.m-3), station 14 (202.371 cells.m-3), station 18 (196.983 cells.m-3) and station 46 (187397 cells.m-3). Meanwhile, the other stations had an abundance of &lt;150,000 cells/m3. The highest abundance at station 13 was dominated by the genera Bellerochea (64.068 cells.m-3), Chaetoceros (42.407 cells.m-3) and Nitzschia (35.390 cells.m-3). The high abundance of phytoplankton at Station 13 was due to upwelling.

Spring phytoplankton of Lake Onego as a trophic resource for deep-water benthos

In the past few years the relict deep-water crustacean Monoporeia affinis (Lindström, 1855) has become less abundant in Lake Onego, Europe’s second largest lake. Further studies are needed, therefore, to better understand the formation of spring phytoplankton as food for deep-water benthos. The aim of the present project was to study the temperature-dependent vertical distribution of phytoplankton in Petrozavodsk Bay of Lake Onego in the spring season. In May 2019, the total abundance, biomass and species composition of phytoplankton were assessed. The transparency and temperature of Onego water were also measured. The median values of phytoplankton’s total abundance and biomass at various growth stages were 1.15–1.67 M cells/l and 1.96–3.12 mg/l, respectively. The above indices were consistent with the long-term maximum growth of phytoplankton in Petrozavodsk Bay in spring and were not markedly different (p&lt;0.05) from those for spring phytoplankton in 1989-2015, indicating the permanent trophic status of Petrozavodsk Bay in the spring season over the past 30 years. A significant difference (p&gt;0.05) in the vertical distribution of phytoplankton, dominated by Aulacoseira islandica (O. Müll.) Sim diatoms, was found between the stations in May 2019. The reproduction of the relict deep-water crustacean M. affinis, taking place simultaneously with the intensive vegetation and the settling of its major food resource, A. islandica, on the bottom, suggests the formation of favourable feeding conditions for deep-water benthos in Petrozavodsk Bay of Lake Onego.

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.

A lag bloom pattern of phytoplankton after freshwater input events revealed by daily samples during summer in Qinhuangdao coastal water, China.

Phytoplankton blooms have become a global concern due to their negative impacts on public health, aquaculture, tourism, and the economic stability of coastal regions. Therefore, elucidating the shifts in phytoplankton community structure and abundance, as well as their environmental drivers, is crucial. However, existing studies often fail to capture the detailed dynamics of phytoplankton blooms and their environmental triggers due to low temporal observation resolution. In this study, high temporal resolution (daily) samples were collected over 43 days to investigate the influence of environmental factors on phytoplankton in Qinhuangdao in the summer. During the observation period, a total of 45 phytoplankton species were identified, comprising 26 Bacillariophyta species, 16 Dinophyta species, 2 Euglenophyta species, and 1 Chromophyta species. Interestingly, a lag bloom pattern of phytoplankton behind freshwater input was observed across day-to-day samples. Phytoplankton blooms typically lagged 1-3 days behind periods of decreased salinity and nutrient input, suggesting that freshwater influx provides the foundational materials and benefits for these blooms. Moreover, the phytoplankton blooms were triggered by six dominant species, i.e., Chaetoceros spp., Pseudo-nitzschia delicatissima, Skeletonema costatum, Protoperdinium spp., Leptocylindrus minimus, Pseudo-nitzschia pungens, and Thalassiosira spp. Consequently, the succession of phytoplankton showed a predominant genera shift in the following sequence: Nitzschia, Protoperdinium, and Prorocentrum - Skeletonema - Pseudo-nitzschia - Gymnodinium - Leptocylindrus. Besides that, a deterministic process dominated phytoplankton community assembly across time series, and DIP is a key factor in shifting the phytoplankton community structures in this area. In summary, our study offers high-resolution observations on the succession of phytoplankton communities and sheds light on the complex and differentiated responses of phytoplankton to environmental factors. These findings enhance our understanding of the dynamics of phytoplankton blooms and their environmental drivers, which is essential for the effective management and mitigation of their adverse impacts.

Состав и структура фитопланктона Сылвенско-Чусовского плеса Камского водохранилища (Россия)

Based on the materials from studies of phytoplankton in the SylvenskoChusovsky reach of the Kama Reservoir in July 2020 and 2022, its taxonomic composition, ecological-geographical structure and quantitative indicators were studied. The large marginal Sylvensko-Chusovsky reach of the Kama Reservoir is formed by the confluence of the Sylva and Chusovaya rivers and includes two districts and three sections (See Fig. 1). The mineralization of water throughout the reach varies significantly, from 225 to 1000 mgL-1, which is associated with the influx of river water. In the Sylva River, the average mineralization values in summer are significantly higher (650 mgL-1) than those of the Chusovaya River (250 mgL-1). Precipitation and surface inflow volumes in the study area (July 2020 and 2022) were below long-term averages. The years of research varied significantly in temperature regime: the water temperature of the Sylvensko-Chusovsky reach in 2020 was 30.3 ± 1.6°С, in 2022 – 20.3 ± 0.6°С. As a result of the study, 267 species and intraspecific taxa of algae from 9 departments were identified in the phytoplankton composition of the Sylvensko-Chusovsky reach of the Kama Reservoir. The basis of the species richness was formed by diatoms (36.0%), green (28.5%), golden (12.5%) algae, and cyanoprokaryotes (11.6%); the share of other algae departments totaled 11% (See Table 1). The species composition of phytoplankton differs in various parts of the reach, which is associated with the flow of river waters from the Sylva and Chusovaya rivers into the bays; the degree of floristic similarity according to the Sørensen-Chekanovsky coefficients is low and ranges from 0.41 to 0.68 (See Fig. 2). As a result of the carried-out work, the floristic list of algae of the Sylvensky Bay was replenished by 41%, previously numbering 69 species and varieties from 5 departments (See Fig. 3). In the ecological and geographical aspect, the algal flora of plankton is represented by typically planktonic species, widespread in water bodies of the globe, indifferent to water salinity, living only in fresh water bodies and preferring neutral waters (See Table 2). In Sylvensky Bay, the ecological structure of algocenoses retained its proportions from 2004 to 2022. During the summer low-water period of algal flora, the most significant contribution is made by cyanoprokaryotes, which appear with diatoms and green sea waves (See Fig. 4). Quantitative indicators of phytoplankton development varied significantly: abundance from 0.9 to 85.0 million cellsL-1, biomass from 0.39 to 13.02 mgL-1. Differences in the temperature regime during the years of the study determined the level of phytoplankton development; in 2022, the abundance and biomass values were three times higher compared to the abnormally hot 2020 (See Table 3). Throughout the entire water area, the dominant complex in number is represented mainly by species indicators of anthropogenic eutrophication (Aphanizomenon flos-aquaе, Aphanocapsa holsatica, Aulacoseira granulata, Stephanodiscus binderanus) and there is a massive development of non-heterocyst cyanoprokaryotes (Aphanocapsa holsatica, A. inserta, Anathece clathrata, Planktolyngbya limnetica, A. phanothece bachmannii). Dinophyte algae (Apocalathium aciculiferum, Peridinium cinctum, P. willei, Peridinium sp. and Gymnodinium sp.) played a significant role in the composition of dominant species by biomass, along with diatoms (See Table 4). As a result of the development of smallsized algal species, phytoplankton abundance values have increased more than 20-fold from 2004 to the present, while phytoplankton biomass has increased only twofold. The Shannon species diversity index values (2.96-5.02) indicate a complex structure and high biodiversity of phytoplankton. Higher index values were characteristic of riparian areas in 2022. Simpson's indices, reflecting the degree of expression of dominance of certain species, vary from 0.04 to 0.36 in the Sylvensko-Chusovsky Bay. The decrease of the index in the Chusovsky Bay (0.15 ± 0.03) is associated with a higher diversity of phytoplankton compared to the Sylvensky Bay (0.23 ± 0.05). Based on the composition of structure-forming species and the level of biomass, the trophic status of the Sylvensko-Chusovsky reach is determined as mesotrophic. Since the distribution of phytoplankton across the water area is uneven, the trophic state was assessed from β-oligotrophic in the Sylvensko-Chusovsky area to mesotrophic in the bays in 2020, and from mesotrophic to α-eutrophic level in 2022. The main changes in phytoplankton include a significant increase in the taxonomic diversity of golden algae, an increase in the coenotic role of disazotrophic cyanoprokaryotes and dinophyte algae, which indicates the progressive eutrophication of the waters of the Sylvensko-Chusovsky reach under the combined influence of anthropogenic factors and climate warming.

The Community Structure of Plankton at Floating Net Cages Aquaculture Area in Sendang Biru Water Indonesia

The leftover food and feces from fish aquaculture in the floating net cages (FNC) may contribute to the nutrient enrichment at surrounding FNC water. The phytoplankton community structure is the one of important indicator for water quality evaluation. This research aims to determine the plankton community structure and water quality around FNC, Sendang Biru, Malang. Plankton samples and physico-chemical parameters were taken at 3 locations at surrounding FNC area. The results show that phytoplankton from the Bacillariophyceae class and zooplankton from the Hexanauplia class (copepods) dominate in the community structure. Phytoplankton abundance ranges from 795-11405 ind/L, diversity index (H') ranges from 1.47-2.43, evenness index (E) ranges from 0.76-0.95, and dominance index (D) ranges from 0.1-0.3. Meanwhile, zooplankton abundance ranges from 15-634 ind/L, H' value in range of 2.05-2.58, E value in the range of 0.72-0.84, D value in the range of 0.11 -0.17. Nitrate and phosphate have values that exceed the specified quality standards.

Application of organic fertilizer made from solid waste from shrimp ponds for tilapia nursery (Oreochromis niloticus)

The solid waste of super-intensive aquaculture ponds can be used as organic fertilizer. Organic fertilizers are useful in soil nutrient enrichment and improvement. The purpose of this study was to utilize the solid waste of super-intensive ponds as an organic fertilizer for the nursery of tilapia (Oreochromis niloticus). The treatments applied were: (A) organic fertilizer of solid waste of shrimp ponds with a dose of 0.1 kg/m2, (B) organic fertilizer of solid waste of shrimp ponds with a dose of 0.2 kg/m2, (C) organic fertilizer of solid waste of shrimp ponds with a dose of 0.3 kg/m2, (D) without organic fertilizer (control). The parameters observed were the growth of natural feed (plankton), tilapia’s growth and survival rate, and water quality. The growth and survival rate data were analyzed using oneway ANOVA, while water quality and natural feed data were analyzed descriptively. The result showed that the absolute growth of tilapia obtained during the study ranged from 0.1955-0.3158 g/ind with SGR 0.6517-1.0527%/day. The highest phytoplankton abundance in treatment A was 102858 ind/L, and zooplankton was 70354 ind/L. The study’s water quality supported tilapia’s growth and natural feed.

Factors affecting abundance and primary productivity of phytoplankton in a wetland ecosystem of Bangladesh

Wetlands are the most productive, economically important and hydrologically variable ecosystems. In this study, the abundance of phytoplankton and its primary productivity were evaluated in Dingapota Haor of Bangladesh. A total of 41 phytoplankton genera belong to Chlorophyceae (15), Bacillariaophyceae (14), Cyanophyceae (8) and Euglenophyceae (4) were recorded whereas Bacillariaophyceae (37.02%) was the most dominant. The highest cell density (22.71×104 cell L–1) was recorded in pre-monsoon. Diversity indices were also significantly higher in pre-monsoon. The species diversity, evenness and richness varied from 2.51–3.79, 0.57–0.90 and 4.65–7.50 respectively. Difference in phytoplankton assemblage with an overall average dissimilarity value of 52.56 % was recorded. Cyclotella (3.60%), Bacillaria (3.13%), Volvox (2.95%), Spirulina (2.92%) and Euglena (2.88%) were the five most contributory species to the seasonal variation. Gross Primary Production, Net Primary Production and Community Respiration values ranged from 0.90–2.49, 0.68–1.60 and 0.35–0.89 mgCm–3day–1 respectively. Alkalinity and Chl-a showed significant positive correlation with GPP, NPP and CR. Pre-monsoon was the most productive phase whereas the monsoon season was the least productive. The current study produced valuable baseline data that will aid in the formulation of wetland conservation and management strategies.

Algae–zooplankton relationships during the year-round cyanobacterial blooms in a shallow lake

Cyanobacterial blooms have a strong impact on the food web structure, interactions and ecosystem functioning. The aim of this study was to describe the seasonal changes in composition and abundance of heterotrophic nanoflagellates, ciliates, rotifers, and crustaceans in relation to algae and nutrients in a shallow eutrophic lake (north-eastern Poland) dominated by cyanobacteria and exposed to the strong impact of cormorants. Our results showed that algae accounted for a small part of the total phytoplankton abundance (9–40%) and biomass (10–21%) and were dominated by diatoms and cryptophytes. All of the studied groups of planktonic organisms were quite rich in species (95 algal, 79 ciliate, 44 rotifer and 25 crustacean species) and relatively abundant. Copepods formed a substantial part (45–83%) of the total zooplankton biomass during all seasons. Relatively low algal to zooplankton biomass ratio (0.8–1.1) suggests that during spring, summer, and winter algae were not sufficient food resources for metazooplankton, which supplemented its diet with protists (heterotrophic nanoflagellates and ciliates). In a shallow lake dominated by cyanobacteria, winter (ice-covered period) may be a more favourable period for the growth of some groups of algae, ciliates and rotifers than other seasons due to decreasing abundance of cyanobacteria.

Impact of wildfire ash on bacterioplankton abundance and community composition in a coastal embayment (Ría de Vigo, NW Spain)

Wildfire ash can have an impact on coastal prokaryotic plankton. To understand the extent to which community composition and abundance of coastal prokaryotes are affected by ash, two ash addition experiments were performed. Ash from a massive wildfire that took place in the Ría de Vigo watershed in October 2017 was added to natural surface water samples collected in the middle sector of the ría during the summer of 2019 and winter of 2020, and incubated for 72 h, under natural water temperature and irradiance conditions. Plankton responses were assessed through chlorophyll a and bacterial abundance measurements. Prokaryotic DNA was analyzed using 16S rRNA gene partial sequencing. In summer, when nutrient concentrations were low in the ría, the addition of ash led to an increase in phytoplankton and bacterial abundance, increasing the proportions of Alteromonadales, Flavobacteriales, and the potentially pathogenic Vibrio, among other taxa. After the winter runoff events, nutrient concentrations in the Ría de Vigo were high, and only minor changes in bacterial abundance were detected. Our findings suggest that the compounds associated with wildfire ash can alter the composition of bacterioplanktonic communities, which is relevant information for the management of coastal ecosystems in fire-prone areas.

Temperature driving vertical stratification regulates phytoplankton community structure in the Bohai Sea and Yellow Sea

To analyse the effects of physicochemical factors on the phytoplankton community in the Bohai Sea (BS) and Yellow Sea (YS), a investigation was conducted during 27 July to 10 August 2020. A sum of 156 species were identified in the BS and YS, including Bacillariophyta (69 species), Pyrrophyta (85 species) and Chrysophyta (2 species). The phytoplankton community were divided into four provinces according to Bray–Curtis similarity. In order to study the phytoplankton community in the BS and YS, we studied the phytoplankton community composition and their assembly mechanisms. The results showed that stochastic ecological processes had a greater effect on the province C community structure. The Raup-crick dissimilarity showed that deterministic factors had a greater effect on the province A, B and D communities structure. The habitat niche width results indicated that niche was larger in the province D, compared to the province A, B and C. Based on a structural equation model (SEM), we analyzed the effects of physicochemical factors on phytoplankton community structure and temperature was found to affect the phytoplankton community composition and structure by the vertical stratification. The result showed that temperature was an important parameter for phytoplankton abundance and revealed that temperature affected phytoplankton community structure by influencing the vertical stratification index (VSI) in the BS and YS.

Hydrochemical conditions and phytoplankton in the Kievka estuary (Japan Sea) with calculation of primary production by phosphorus utilization

Spatial distribution of chemical parameters, as concentration of dissolved inorganic phosphorus (DIP), inorganic silica, nitrite nitrogen, nitrate nitrogen, ammonium nitrogen, total iron, dissolved oxygen, and biochemical oxygen demand (BOD5) is considered together with species composition, abundance and biomass of phytoplankton on the data of complex survey conducted in the estuary of the Kievka River in May 2020, with special attention to DIP and phytoplankton variations along the salinity gradient in the zone of mixing fresh and saline waters. In the lower Kievka, phytoplankton was studied for the first time. The phytoplankon biomass varied from 0.05 to 0.21 g/m3, proportional to changes in primary production calculated from the DIP balance in the river water moving downstream through the estuary (from 0.02 to 0.23 g/m3km). The highest production and the highest biomass were found in the upper part of the external estuary. The water of Kievka River was initially poor in nutrients, so primary production in its estuary was supported by DIP regenerated in the process of organic matter mineralization in the internal estuary.