Abstract Phytoplankton communities are sensitive to global change drivers, yet the combined effects of warming and nutrient enrichment remain insufficiently explored in tropical freshwater ecosystems. Here, we tested the individual and interactive effects of increased temperature and eutrophication on phytoplankton structure using outdoor mesocosms in a tropical region. We hypothesized that both stressors would influence community responses, promoting higher phytoplankton density, increased chlorophyll- a , reduced species richness, and shifts toward tolerant Chlorophyta and Cyanobacteria, with stronger effects expected when warming and nutrient enrichment occurred together. We monitored limnological conditions and phytoplankton composition to capture short-term ecological responses. Nutrient enrichment triggered pronounced changes in water conditions, including higher turbidity, conductivity, dissolved oxygen, and chlorophyll- a , accompanied by clear shifts in phytoplankton density and species composition. Warming alone produced subtle effects but slightly reinforced eutrophication-driven increases in chlorophyll- a and influenced some limnological variables. Species richness remained stable across treatments, while Chlorophyta dominated under nutrient-rich conditions, reflecting their advantage in tropical eutrophic environments. Overall, eutrophication was the primary driver of phytoplankton responses, whereas warming acted as a secondary, modulatory factor. These findings highlight the heightened vulnerability of tropical freshwater ecosystems to nutrient enrichment and underscore the need to integrate nutrient reduction policies with climate change adaptation in freshwater management.
Andrade et al. (Thu,) studied this question.