Anthropogenic pressure drives phytoplankton and zooplankton biodiversity homogenization in tropical coastal lagoons of different conservation statuses

Even though ecologically complementary, contrasting phyto- and zooplankton responses to anthropogenic pressures are scarcely applied to tropical coastal lagoons. We hypothesize that anthropogenic pressure acts as a local environmental filter, promoting biotic homogenization of plankton communities across tropical coastal lagoons. Coastal lagoons under different conservation statuses were sampled (wet and dry periods) to measure photosynthetic pigments, nutrient concentrations, salinity, oxidation–reduction potential, dissolved oxygen (DO) and phyto- and zooplankton communities. Linear regression was applied, controlling for geographical distance, to identify the main factors affecting plankton β-diversity components. Sampled stations were classified based on trophic conditions and clustered based on environmental variables for further analysis of the plankton assemblages associated with each cluster. Distance-based linear model analysis (DistLM) was used to examine the relationship between biotic and abiotic variables. Supereutrophic and hypereutrophic lagoons had significantly lower β-diversity values, with turnover dominance over nestedness. DistLM revealed inorganic carbon, DO, chlorophyll pigments and salinity as key environmental drivers of plankton community structure. Environmental variables structured phyto- and zooplankton composition across the lagoons, acting as environmental filters and supporting the hypothesis of an ongoing biotic homogenization process in hypereutrophic lagoons. Our findings highlight the importance of eutrophication control for preventing biodiversity loss in coastal lagoons.