Eutrophication drives functional and beta diversity loss in epiphytic cyanobacteria

The structure of epiphytic cyanobacteria and patterns of beta- and functional diversity are crucial for understanding how aquatic environments respond to disturbances. This study evaluated how epiphytic cyanobacteria's biomass, adaptive strategy groups, and beta- and functional diversity components respond to increasing eutrophication and environmental homogenization in three tropical reservoirs. Hypereutrophic conditions supported greater biomass of competitive species (C-strategists), while stress-tolerant (S-strategists) were more abundant in oligo-mesotrophic waters. In contrast, ruderal species (R-strategists) were most abundant in the eutrophic system and influenced by rainfall. Total beta-diversity and turnover were significantly lower in eutrophic and hypereutrophic systems, correlating with greater environmental homogenization. The oligo-mesotrophic reservoir presented a higher local contribution to beta-diversity, highlighting the presence of unique species. Communities in the hypereutrophic system were subsets of species from richer communities, exhibiting higher nestedness. Eutrophication also negatively impacted functional diversity, with eutrophic and hypereutrophic environments showing lower functional evenness, divergence, dispersion, and dissimilarity, and higher functional redundancy due to the loss of unique functions. These results emphasize the detrimental impact of eutrophication on beta- and functional diversity of epiphytic cyanobacterial communities, underscoring the need for eutrophication control measures in tropical reservoirs.