Soft‐Bottom Bivalves (Mollusca) in an Impacted Brazilian Marine Protected Area and Adjacent Regions

ABSTRACT Bivalves are a key group in benthic assemblages. Besides, little is known about this fauna, especially in marine protected areas (MPAs) from neotropical regions, for example, in Brazil. Here, we provide the results of the taxonomic composition and ecology of bivalve assemblages in Xixová‐Japuí State Park (XJSP), an MPA from the southeastern Brazilian coast, severely impacted by human activities in its surrounding areas. Sediment sampling was performed at four sites within the MPA boundaries and near two submarine outfalls close to the MPA. The samples were sieved, and the retained organisms were identified to the lowest possible taxonomic level. Community ecology metrics were then applied at each sampling site. A total of 228 whole specimens and two empty shells were collected, representing 20 bivalve species, of which two may represent new species to science or juveniles of previously known species. The most abundant families were Tellinidae (63 specimens) and Mactridae (57 specimens). These two families, together with unidentified species (51 specimens), account for more than 78% of the individuals. No differences were found for most community descriptors; however, multivariate analysis revealed shifts in assemblage composition between the MPA and sites affected by submarine outfalls, with higher overall abundances in the latter. The results of this study are important for the MPA management plan, as they provide an accurate, taxonomically precise inventory that supports conservation efforts. Additionally, a more thorough ecological risk assessment of the contaminated sediments surrounding MPAs is anticipated once non‐targeted species are properly inventoried.