Anthropogenic nutrient inputs drove shifts in phytoplankton productivity and community structure in the northern South China Sea over the past century.

Disentangling phytoplankton regime shifts and ecosystem stability under water diversion: Insights from functional traits and trophic interactions in a mesocosm experiment.

Abstract Phytoplankton play a crucial role in regulating marine biogeochemical pathways but studying their spatial and temporal dynamics often requires extensive and laborious oceanographic expeditions. Here, we report a novel use of Biogeochemical‐Argo data to delineate planktonic habitats in the Tropical North Atlantic Ocean (TNA). We then investigated the phytoplankton biomass via in situ measurement of the BGC‐Argo floats and phytoplankton community structure of each habitat using Phytoplankton Functional Types derived from satellite observations. Our habitat delineation approach provided a finer scale and dynamic overview of phytoplankton assemblages and their surrounding environment, complementary to the widely used and static biogeochemical provinces of Longhurst. While picophytoplankton remained dominant for most communities, we found elevated abundance of microphytoplankton, including diatoms and dinophytes, and nanophytoplankton, including haptophyte and green algae, following the seasonal displacement of the Intertropical Convergence Zone, and the Amazon and Orinoco River discharges into the Tropical Atlantic and Eastern Caribbean Sea. At midlatitude, our method was able to capture both the seasonal and spatial variations of the oligotrophic region of the North Atlantic subtropical gyre. These findings shed light on the seasonality of phytoplankton distribution driven by meteorological and oceanic forcings and demonstrated the potential of the BGC‐Argo in studying and monitoring marine ecosystem.

Monitoring phytoplankton from space can help detect shifts in marine ecosystems, particularly under accelerating climate change. However, most existing ocean-colour chlorophyll-a (Chl-a) algorithms are empirical in nature, and do not explicitly consider any potential optical effects of shifts in phytoplankton community composition independent of a change in Chl-a. Similar ocean-colour signals may arise from different combinations of Chl-a and phytoplankton community composition. Revealing how phytoplankton are responding to environmental change using satellite data requires tackling this ambiguity. In previous work, we developed an Ocean Colour Modelling Framework (OCMF) to simulate ocean colour for varying Chl-a and phytoplankton size classes (PSCs). Here, we invert the OCMF to directly retrieve Chl-a, key inherent optical properties (IOPs), and PSCs, from satellite remote sensing reflectance and sea surface temperature (SST), accounting for deviations in non-algal particles (NAP) and coloured dissolved organic matter (CDOM) from assumed open ocean relationships with Chl-a. The model is validated using a global in situ dataset and shows stable performance across diverse oceanic conditions. Integrating ecological concepts into a bio-optical model may advance our ability to interpret long-term changes in phytoplankton community structure from space.

Salinity and nutrient driven shifts in diatom dominance along the Tamil Nadu coast during the northeast monsoon.

Impacts of stratified water column on summer phytoplankton community structure and dynamics in the East Sea, Korea

Environmental DNA reveals shift in phytoplankton community driven by sewage-derived eutrophication in coastal waters.

Triazine herbicides inhibit phytoplankton photosynthesis in the East China Sea: A species-specific assessment.

The phytoplankton community structure is regulated by environmental conditions, influencing ecosystem stability and productivity. In August 2023, a survey was conducted at 28 stations in the Yellow River Estuary (YRE) and adjacent coastal waters, where phytoplankton communities, nutrients, chlorophyll-a, and other environmental factors were synchronously analyzed. Across-site comparison, redundancy analysis (RDA), and K-means clustering were applied to characterize spatial patterns and identify key factors controlling diatom to dinoflagellate ratios and dominant taxa. The nutrient structure, particularly DIN/PO43−, corresponded closely with the spatial shift between diatom and dinoflagellate dominance. Offshore areas dominated by diatoms (Cerataulina, Chaetoceros) exhibited higher salinity and more balanced nutrient ratios, whereas nearshore zones influenced by Yellow River inputs had high DIN, low PO43−, and evident phosphorus limitation, favoring dinoflagellates (Noctiluca, Heterodinium). These results indicate that nutrient imbalance and salinity gradients are likely the main drivers of diatom-to-dinoflagellate transitions and shape the phytoplankton composition in the estuary coastal waters. This study provides insights linking nutrient imbalance to phytoplankton community succession and advances the understanding of estuarine phytoplankton dynamics.

The Xiaohai Lagoon is a vital coastal ecosystem that has faced decades of significant natural and anthropogenic pressures. This study investigated the spatio-temporal dynamics its phytoplankton communities through quarterly sampling from 2024 to 2025. Significant spatial and seasonal variations (p < 0.05) in physicochemical parameters were observed. The concentrations of various physicochemical parameters were highest at the lagoon mouth and decreased inwards. In contrast, sites inside the lagoon experienced elevated nutrient and organic matter indicators. Seasonally, the highest temperatures were recorded in Summer. However, Autumn recorded the highest NH3-N and NO2-N levels, while Winter recorded the highest NO3-N levels. The findings generally suggest minimal pollution, as key physicochemical parameters, met the China water quality standard for environmental protection (GB 3838–2002). Overall, 109 phytoplankton species belonging to 38 genera and 5 phyla, including Cyanophyta, Bacillariophyta, Chlorophyta, Cryptophyta, and Dinophyta, were identified. The phytoplankton average density was 1.65 × 103 Ind L−1 with insignificant differences both spatially and seasonally (p > 0.05). One-way ANOSIM indicated significant seasonal dissimilarity in phytoplankton community composition (R = 0.828, p < 0.001), with SIMPER results revealing that Ceratocorys sp., Chaetoceros sp., Coscinodiscus subtilis, Oscillatoria princes, and Thalassionema nitzschioides contributed to the seasonal difference. CCA indicated phytoplankton composition and abundance were influenced by COD, TN, TDS, salinity, oxidation-reduction potential, EC, water temperature, NH3-N, and NO3-N. This study highlights the critical need for effective management strategies to protect and preserve the ecological integrity of Xiaohai Lagoon.

To investigate the seasonal dynamics of phytoplankton community structure and its relationship with environmental factors in the coastal waters of the Leizhou Peninsula, China, surveys were conducted at 21 stations during four seasonal cruises: autumn (August 2022), winter (December 2022), spring (March 2023), and summer (June 2023). A total of 174 phytoplankton species from 7 phyla were identified. Species richness peaked in summer (93 species, 5 phyla), followed by winter (80 species, 3 phyla), spring (79 species, 5 phyla), and autumn (75 species, 5 phyla). Bacillariophyta dominated throughout the year, with Skeletonema costatum (Greville) Cleve, 1878 and Chaetoceros lorenzianus Grunow, 1863 being consistently dominant across all seasons. Phytoplankton cell density showed a distinct seasonal pattern, highest in autumn, followed by summer, and lower in spring and winter. Diversity indices (H, J, D) indicated moderately to heavily polluted waters. Redundancy analysis identified salinity, dissolved inorganic nitrogen, chlorophyll a (Chl a), pH, water temperature, chemical oxygen demand, and dissolved silicon as key environmental drivers, with their influence varying seasonally: salinity was strongest in summer, Chl a in winter, and multiple factors jointly shaped the community in spring and autumn. This study provides a comprehensive assessment of phytoplankton biodiversity and clarifies the environmental drivers of their distribution in the coastal waters of the Leizhou Peninsula, China.

ABSTRACT The coastal zone of the northern Patagonian Continental Shelf is a biologically productive and optically complex region. This study evaluated the performance of the Quasi-Analytical Algorithm (QAA) in assessing the temporal variability and trends of the phytoplankton absorption coefficient at 443 nm (a ph(443)) using an extensive in situ dataset (39°S–62.5°W; 41.5°S–60°W) and 18 years (2003–2021) of MODIS-Aqua imagery. Seventy-five samples were collected from January to March 2020 aboard artisanal fishing boats. Measurements included turbidity, suspended particulate matter (SPM), chlorophyll-a (Chl-a), phytoplankton absorption (a ph(λ)), and species composition. Results showed that higher Chl-a concentrations were associated with greater turbidity and lower specific absorption (a ph*(443)). Variations in a ph*(443) were strongly linked to phytoplankton community structure and packaging effects, with large diatoms (e.g. Coscinodiscus, Pseudosolenia) reducing a ph*(443) and causing slight overestimations in satellite-derived a ph(443). Despite these biases, QAA remained robust, showing good correlation with in situ data and low sensitivity to turbidity changes. Time series decomposition using Census X-13 revealed a substantial irregular component, contributing 28–50% of the total variance, possibly due to sub-mesoscale processes and storm events. A significant monotonic increase in a ph(443) was detected across the study area, aligning with previous trends observed on the Patagonian Shelf.

Abstract Sunlight-stimulated chlorophyll fluorescence offers potential for assessing phytoplankton physiological status at broad scales detected by satellites, but controls on these signals are poorly constrained. In this study, we present a comprehensive, high-resolution dataset of passive chlorophyll fluorescence alongside potential physical and biogeochemical drivers collected across the Benguela upwelling system and South Atlantic Subtropical Gyre. The nutrient limitation status of phytoplankton was assessed through 27 onboard bioassay experiments. A consistent and significant difference in light-saturated, passive chlorophyll fluorescence normalized to phytoplankton absorption ( $$F/{{a}_{{{\mathrm{ph}}}}}_{\max }^{{{\rm{passive}}}}$$ F / a ph max passive ) was observed between waters where phytoplankton were either iron or nitrogen limited, with iron limited regions showing threefold higher $$F/{{a}_{{{\mathrm{ph}}}}}_{\max }^{{{\rm{passive}}}}$$ F / a ph max passive compared to nitrogen limited regions. When interpreted alongside the results of the bioassay experiments, we found that neither variability in physical forcing (temperature, mixing, light climate) or phytoplankton community structure could explain the major variability in $$F/{{a}_{{{\mathrm{ph}}}}}_{\max }^{{{\rm{passive}}}}$$ F / a ph max passive . These results provide direct field-based evidence that passive chlorophyll fluorescence is sensitive to phytoplankton nutrient limitation and demonstrates potential for observation at high spatial and temporal resolution using satellite observations.

Algal community can alter the role of a drinking water Reservoir as a CO2 source or sink at different seasons.

Mesozooplankton grazing patterns and preferences during a cyanobacterial harmful algal bloom (cHAB) in a large eutrophic lake.

ABSTRACTThe health of subtropical transboundary coastal rivers is closely linked to phytoplankton diversity, seasonal fluctuations, and community structure. This study presents the first comprehensive multivariate assessment of phytoplankton diversity and environmental drivers in the Dakatia River. Canonical Correspondence Analysis (CCA), Analysis of Similarity (ANOSIM), and Similarity Percentage (SIMPER) were applied across eight geo‐referenced stations under varying anthropogenic pressures to establish a baseline data for this cage‐culture–intensive river system. The analysis revealed distinct spatial and seasonal variations in phytoplankton diversity and taxonomic composition, highlighting shifts in community assemblages and the influence of physicochemical factors on these dynamics. A total of 37 genera were identified across six major classes: Bacillariophyceae (36.50%), Chlorophyceae (25.91%), Cyanophyceae (17.00%), Euglenophyceae (13.20%), Ulvophyceae (5.06%), and Zygnematophyceae (2.31%). Phytoplankton abundance was highest in winter (16,958.33 ± 6418.75 cells L−1), followed by the monsoon (14,572.92 ± 2982.90 cells L−1) and summer (13,739.60 ± 1857.76 cells L−1). The Shannon–Wiener diversity index, species evenness, and species richness exhibited seasonal fluctuations, ranging from 2.14 ± 0.22 to 2.47 ± 0.15, 0.65 ± 0.07 to 0.75 ± 0.07, and 2.67 ± 0.55 to 4.29 ± 0.38, respectively, reflecting a moderate level of phytoplankton diversity in a dynamic and complex river ecosystem. Cluster analysis delineated five distinct phytoplankton communities at a 50% similarity threshold. ANOSIM results indicated significant seasonal dissimilarity (p < 0.001), while no significant spatial dissimilarity (p > 0.05) was observed. SIMPER analysis identified Melosira sp. as the primary contributor to interseasonal dissimilarities, followed by Oscillatoria sp. and Gomphosphaeria sp. Pearson's correlation and CCA highlighted ammonia, temperature, salinity, nitrate, and phosphate as key environmental drivers shaping phytoplankton abundance, diversity, and community composition. These findings have provided critical insights for ecosystem management, biodiversity conservation, and sustainable water resource governance.

Microcystin-RR (MC-RR), a common cyanotoxin frequently detected in freshwater ecosystems, can influence phytoplankton dynamics by altering the growth patterns of coexisting species. While a large body of work has examined the allelopathic effects of microcystin-RR (MC-LR) and other microcystin variants, there are relatively few studies that specifically address the impact of pure MC-RR on phytoplankton species, particularly those that themselves produce this toxin, under environmentally relevant concentrations. This study investigated the effects of an environmentally relevant concentrations of MC-RR (1, 5, and 10 µg L⁻¹) on the growth of five phytoplankton species: three cyanobacteria (Trichormus variabilis, Nostoc sp., Microcystis sp.) and two green microalgae (Chlorella sp., Scenedesmus sp.), under laboratory conditions. Growth responses were monitored spectrophotometrically to determine chlorophyll a concentration over a 14-day period. Additionally, MC-RR was identified and quantified in the treated cyanobacterial cultures using the HPLC-DAD technique. The results demonstrated species-specific responses. MC-RR exhibited a stimulatory effect on both green algae species. In contrast, T. variabilis showed progressive growth inhibition, which became statistically significant after day 5. Nostoc sp. displayed slight, nonsignificant inhibition, while Microcystis sp. showed tolerance to MC-RR exposure. These findings demonstrate the allelopathic potential of MC-RR, with species-specific effects on growth that reflect differential sensitivity among phytoplankton taxa. The results underscore the ecological relevance of this toxin in shaping phytoplankton community structure and species interactions in freshwater ecosystems.

Microniche shape phytoplankton community structure in inter-connecting creeks within a mangrove ecosystem

Ecological Drivers of Phytoplankton Community Structure in Egbe Reservoir, Southwestern Nigeria

Impact of atmospheric dust on phytoplankton dynamics and primary productivity in the tropical marine ecosystem of the Eastern Arabian Sea.