Coastal lagoons are systems threatened by anthropogenic pressures. In order to develop and apply adapted management strategies, it is essential to understand their ecological functioning. In particular, eukaryotic plankton communities play a fundamental role in sustaining the entire trophic network and functioning of the ecosystem. We used DNA-metabarcoding to study seasonal diversity and trophic interactions of plankton communities in three Corsican coastal lagoons with contrasting morphologies and functioning. The main results demonstrate the influence of seasonal and morphological factors on community structure and trophic relationships among these planktonic communities. Biguglia favors an herbivorous food web but is dominated by mixoplankton, Urbino is distinguished by a high diversity of heterotrophic protists, and Santa Giulia by the development of picophytoplankton and the emergence of a protozooplankton community. This study also shows the emergence of mixoplankton including potentially harmful dinoflagellates present in the three lagoons, and sometimes dominant, linked to anthropogenic pressure, and highlights their integration into the trophic networks in relation to the lagoon characteristics. This is a fundamental step towards understanding plankton succession and ecological network functioning in different coastal lagoon configurations, and thus towards the thoughtful management of these ecosystems under current and future pressures.
Body size is a key functional trait influencing trophic interactions; energy transfer; and community structure in freshwater ecosystems. We examined patterns of adult body size and size variability in cladocerans across a broad elevational gradient (0–3600 m) and multiple freshwater habitats in the Pearl River Basin; China. Using hierarchical mixed-effects models; we quantified the relative contributions of taxonomic structure; environmental gradients; and spatial factors to variation in body size. Mean body size was strongly structured across taxonomic levels; with family and genus accounting for most of the variance; whereas species-level and spatial components contributed comparatively little. After accounting for hierarchical structure; mean body size increased significantly with elevation (approximately 3
Algal communities are sensitive indicators of lake ecosystems, yet their seasonal dynamics remain poorly understood in subtropical Ramsar sites in the hilly region. This study assessed how physicochemical variability shapes algal diversity in Dipang and Khaste Lakes within the Lake Cluster of Pokhara Valley, Nepal. Water and algal samples were collected from 24 sites for each lake during wet and dry seasons and analyzed using correlation and multivariate ordination techniques. A total of 82 species (10 classes) in Dipang and 99 species (8 classes) were recorded in Khaste, with Bacillariophyceae and Zygnematophyceae dominating both lakes. Shannon-Wiener diversity was consistently higher in the wet season, while evenness remained relatively stable which indicates seasonal restructuring was driven primarily by changes in richness rather than dominance patterns. Free CO2 and phosphate increased during the wet season in Dipang, while most other parameters, including DO, nitrate, and conductivity, were elevated in the dry season. In Khaste, temperature, dissolved oxygen, free CO2, nitrate, and phosphate peaked during the wet season, whereas pH, total dissolved solids, conductivity, and hardness were higher in the dry season. Correlation analysis indicated that nitrate positively influenced algal species richness, whereas higher conductivity was associated with reduced richness, showing the differential effects of nutrients availability and ionic conditions on algal communities. Multivariate ordination confirmed that algal composition tracked seasonal environmental shifts. These findings demonstrate that despite lying within the same physiographic zone, Dipang and Khaste Lakes differ remarkably in nutrient dynamics and algal community trajectories. The study underscores the value of algae as ecological indicators and highlights the importance of continuous, site-specific monitoring to guide wetland management and eutrophication control.
Lake Sevan (Caucasus region, Armenia) is one of the largest freshwater high-mountain lakes in the world (1280 km2). Meiofauna was collected at depths from 0 to 63 m in July and October, 2024 to explore its recent state compared with historical data from 1930s and 1980–90s. Total abundance reached a peak at 20–25 m depths but dropped sharply deeper, below the oxycline layer where the hypoxic conditions were observed. Nematodes dominated in numbers of individuals and species (13 species). Harpacticoids were the second in abundance, three species were recorded (Canthocamptus staphylinus, Nitocra hibernica and Nannopus sp.). Mass encystment of C. staphylinus adults were observed in July. Cyclopoida, Oligochaeta, Chironomida, Ostracoda, Turbellaria and Tardigrada were also presented. Abundance of meiofauna was four-to-sixfold lower than thirty years ago. Among crustaceans commonly occurred earlier, harpacticoids, cyclopoids and ostracods decreased in abundance and reduced their depth ranges, whereas cladocerans were absolutely absent. Bathymetric distribution patterns also changed, with single pronounced peak presented at 25-m depth (or 30-m depth for harpacticoids). A shift in the species composition of nematodes was observed, with a transition from sensitive groups towards more opportunistic stress-tolerant forms, and decrease of Maturity Index values. Taken together, these changes indicate the lake environment deterioration, possibly due to increasing eutrophication and oxygen deficiency.
Metabolism is a pivotal process that governs the biogeochemical carbon cycle by both producing and consuming organic matter. Gross primary production (GPP), ecosystem respiration (ER), net ecosystem production (NEP = GPP − ER), and the metabolic balance of GPP and ER were analyzed in Lake Inbanuma from July to December 2023 and May to December 2024. Water temperature, nutrient (nitrate + nitrite, ammonium, phosphate) and chlorophyll a (Chl a) concentrations were also measured. GPP was generally higher in summer and fall than in other seasons, exceeding 10 mgO2 L−1 d−1. GPP and NEP exhibited a significant positive linear relationship. The threshold GPP (when GPP = ER) was 0.75 mgO2 L−1 d−1, markedly lower than values from other eutrophic lakes. GPP/Chl a was significantly positively correlated with phosphate and ammonium concentrations. Furthermore, GPP/Chl a was more affected by phosphate than by ammonium. These results suggest that phosphate concentration is a key factor controlling phytoplankton growth in Lake Inbanuma. NEP remained above zero throughout the study period, with an average GPP/ER ratio of 4.9, suggesting that Lake Inbanuma was autotrophic during the study period. The variations in GPP and NEP were closely related to changes in Chl a concentration, which explained approximately 40
