Spatio-temporal dynamics of phytoplankton community in relation to environmental variables in Lake Maybar, Ethiopia

This study investigated the spatiotemporal dynamics of phytoplankton communities and physicochemical water quality parameters in Lake Maybar across seasonal variations. Sampling was conducted from 2023 to 2025 at three sites to evaluate phytoplankton composition, abundance, and biodiversity in relation to environmental factors. Physicochemical parameters were measured using a multiparameter meter, and nutrient concentrations were analyzed following standard laboratory methods, while phytoplankton samples were collected using a 20 μm mesh plankton net. The results showed that most physicochemical parameters exhibited significant seasonal variation ( p < 0.05) between the wet and dry seasons, except for nitrite, hardness, and pH. A total of 29 phytoplankton species belonging to six taxonomic groups were identified, with Chlorophyta being the dominant group (10 species), contributing 34.48% of the total species composition, whereas Cryptophyta and Dinophyta were the least represented, with one species each. Phytoplankton abundance ranged from 175 to 33,125 cells ml −1 , with the highest abundance recorded at the shoreline sampling site, while Dinophyta showed the highest cell density (33,125 cells ml −1 ). Pielou’s evenness and Shannon–Wiener diversity indices indicated an unstable phytoplankton assemblage, suggesting moderate levels of water pollution in the lake. Redundancy Analysis (RDA) revealed that nitrate, ammonia, total dissolved solids (TDS), total alkalinity, and turbidity were the key environmental variables influencing phytoplankton distribution, with seasonal differences in species–environment relationships. Overall, the findings demonstrate the strong influence of seasonal environmental variability on phytoplankton community structure and provide baseline information for water quality monitoring and ecological management of Lake Maybar.