Population ecology of bivalve mollusks in beach sediments on the southern coast of Espírito Santo, Brazil

This study examined the population ecology of bivalve mollusks on Central Beach in Piúma, southern Espírito Santo, Brazil, over one year (August 2018 to July 2019). Sampling was conducted along four transects perpendicular to the shoreline, with sediment characteristics and benthic community structure analyses. 2,104 individuals were identified, representing 5 orders, 8 families and 13 species. The most abundant species were Anomalocardia flexuosa (39.78%), Strigilla carnaria (28.90%), Donax gemmula (11.93%), and Tivela mactroides (11.07%). The consistent presence of juveniles and recruits indicated that the area serves as a natural nursery for these species. Transect A, closest to the mouth of the Novo River, showed the highest organic matter content in the sediment and the most significant dominance of A. flexuosa, which was positively correlated with organic matter levels (p< 0.0001). Conversely, alpha diversity was negatively correlated with organic matter content (p= 0.0497). Sediment granulometry was uniform across transects, mainly of moderately sorted fine sand. Rainfall did not significantly affect ecological indices or the abundance of dominant species, suggesting that the bivalve community is resilient to seasonal climatic variations. These results highlight the environmental significance of Central Beach in Piúma as a vital estuarine habitat, particularly for A. flexuosa, and emphasize the need for integrated coastal management strategies that account for both marine and continental influences.