Diversity Patterns of Decapod Crustaceans in Small Coastal Rivers of the Atlantic Forest in Southern Bahia, Brazil, During the El Niño Drought of 2015

This study investigated the structure of the decapod crustacean community in first- and second-order coastal rivers of the Atlantic Forest in southern Bahia, focusing on taxonomic composition, abundance, richness, and distribution of species. The main objective was to assess the possible effects of the severe drought of 2015, intensified by the El Niño event, on decapod species, also integrating analyses of land use and land cover by remote sensing. Collections were made in eight rivers between 2015 and 2017. In total, 7075 individuals of eight species were recorded, with Macrobrachium olfersii and M. jelskii being the most abundant in all seasons and locations sampled. Total abundance was higher in the rainy season, although the composition of the communities did not show significant differences between seasons. The Pancadinha and Represa rivers, which were most impacted, showed lower richness and absence of sensitive species such as Atya scabra, M. carcinus, M. heterochirus, and Trichodactylus sp. There were clear differences between impacted and unimpacted rivers. Land use classifications revealed marked changes between 2015 and 2016, with an increase in forest cover, especially in the northern zone. The results show that the combination of seasonality, environmental integrity, and land use shapes the dynamics of these communities.