Diversity and spatial distribution patterns of soft-bottom macrofaunal communities inhabiting two Croatian recreational marinas

The effects of human pressure on benthic macrofaunal assemblages inhabiting touristic marinas have seldom been studied, especially in the eastern part of the Adriatic Sea. In July 2019, we investigated the macrofaunal communities in two Croatian marinas (Špinut and Strožanac) to evaluate the diversity and feeding structure influenced by the morphology of the basins and long-lasting anthropogenic activities. In both marinas, macrofaunal densities and species richness were observed to be higher at the main entrances than at the inner sites. In Špinut, a clear confinement gradient pattern was mirrored in the number of species. In Strožanac, the basin is more open to the sea compared to Špinut, thus the macrofaunal community was not directly influenced by a confinement gradient, despite the presence of boat careening and painting activities. In contrast, Špinut was characterised by a community impoverished in species number near the boathouse area. In both marinas, the variation of the feeding structure was likely driven by grain-size. Subsurface deposit feeders characterised the finer sediments whereas suspension feeders dominated at the sandy-bottom stations. Well-balanced feeding guilds characterised the station near the boathouse in Špinut. However, only a few species represented each trophic guild at this site, indicating possible higher community vulnerability.