Unraveling the taxonomic and functional structure of benthic communities from tropical muddy bottoms chronically disturbed by shrimp trawling

Abstract

The continental shelf provides many important ecosystem services, including coastal protection, recreation, tourism, climate regulation, biodiversity, and food resources. However, this ecosystem has been undergoing degradation due to numerous human activities, both land- and ocean-based, with shrimp trawl fishing being one of the most impactful. This activity physically affects the seabed, alters biological communities, causes biodiversity loss, and compromises ecosystem functions and services. In this research, we characterized the taxonomic and functional structure of epibenthic communities in tropical muddy bottoms chronically trawled by shrimp fisheries on the shallow continental shelf of northeastern Brazil. We tested the hypotheses that: i) the taxonomic and functional structure of the communities is influenced by seasonality and depth, with greater diversity during rainy periods and at shallower depth; and ii) the epibenthic communities exhibit low functional redundancy and high functional vulnerability. Epifauna was studied in two fishing grounds during rainy and dry periods at depths of 10 and 20 m. Communities were dominated by species with traits less sensitive to physical impacts, such as large, hard-shelled scavenger species that crawl on the sediment surface. The taxonomic structure was affected by seasonal variation, whereas the functional structure was more strongly related to fishing grounds. The temporal pattern found may be attributed to seasonal changes in oceanographic parameters, such as salinity and temperature, which differ between dry and rainy periods. These results highlight the vulnerability of epibenthic communities in chronically trawled muddy bottoms of the continental shelf.