Online first articles

Testate amoebae are effective bioindicators of environmental changes in aquatic ecosystems. This study assessed the influence of environmental heterogeneity and seasonality on the structure of testate amoebae assemblages in two Conservation Units in northeastern Brazil: the National Park of Boa Nova (PARNA) and the Wildlife Sanctuary (REVIS), Bahia. Samples were collected from 12 sites during the rainy and dry seasons, alongside abiotic data. We identified 83 taxa, including 26 new records for Bahia. The families Euglyphidae and Hyalospheniidae were the most species-rich. Arcella hemisphaerica Perty, 1852, Centropyxis aculeata (Ehrenberg, 1838), and Euglypha tuberculata Dujardin, 1841 occurred in all samples, with the latter two, along with Cyphoderia ampulla (Ehrenberg, 1840), being the most abundant. Both environmental heterogeneity and season significantly shaped amoebae assemblages, with greater abundance and diversity in the dry season. Rarefaction curves indicated adequate sampling. Cluster analysis distinguished assemblages by rainfall patterns and highlighted the distinctiveness of samples from the Caatinga (P12) compared to ecotonal sites. Redundancy analysis showed that water temperature, transparency, depth, conductivity, dissolved solids, and salinity were key environmental predictors. These findings underscore the importance of considering seasonal and spatial variability in conservation strategies and highlight the relevance of testate amoebae as bioindicators in Neotropical protected areas.