Environmental drivers of waterbird diversity in a world heritage subtropical estuarine system

This study analyzed how environmental, temporal, and spatial variables influenced the distribution and diversity of waterbird assemblages during the dry and rainy seasons in a subtropical estuarine complex in southern Brazil, a world heritage site. From March 2020 to February 2021, we determined the alpha and beta diversities of waterbird in the Paranaguá Estuarine Complex (PEC), southern Brazil, by sampling 36 transects distributed in three bays. Altogether we recorded 46 species distributed in 17 families and eight genera. Despite the similar species richness observed in the dry versus rainy season (41 and 39 species, respectively), we found a weak seasonal influence on the composition of the waterbird assemblage due to the presence of migratory species. Species richness was positively related with water temperature and dissolved oxygen during the wet season. While in the dry season, we recorded a negative relationship between species diversity and turbidity. Despite the great diversity of waterbird species recorded in the PEC, we did not detect a consistent pattern of alpha and beta diversity responses. Balanced variation in abundance was the component that most contributed to total beta diversity, which is consistent for highly mobile species that roam heterogeneous landscapes. Due to their high mobility, waterbird quickly track dynamic features in time and space. The lack of apparent patterns in species distribution and alpha and beta diversity may reflect this dynamic. Our findings reinforce the need to use robust, long-term databases to understand and monitor beta diversity, providing information to support practical actions to protect local and regional biodiversity. Therefore, strategic management plans that use integrated protection networks and aim at biodiversity conservation at different scales must consider these results.