Response of epibenthic faunal assemblages to varying vegetation structures and habitat patch size

Vegetation in shallow coastal marine systems increases habitat complexity and attracts epibenthic fauna. However, these areas are often subjected to dynamic changes such as eutrophication and sedimentation, which may lead to a reduction in patch size and/or a shift in species composition; although, few studies have been performed to show how these alterations affect the fauna assemblages. The aim of this study was to examine whether 4 structurally different types of vegetation, Fucus vesiculosus, Sargassum muticum, Zostera marina and filamentous algae, attract a unique assemblage of epibenthic fauna, compared to each other and to bare sand. Further, the importance of patch size (0.25, 0.5, 1.0 and 2.0 m(2)) on faunal species richness, biomass and assemblage composition within the different vegetation types was investigated. Experimental patches of vegetation were placed in a bay and samples were retrieved after 72 h. Pairwise tests (presence/absence data) showed that the faunal assemblages were significantly different between the vegetation types and also bare sand. Further, the 3 algal treatments (but not the seagrass Z. marina treatment) attracted higher species richness and a higher biomass of motile epibenthic fauna compared to the bare sand habitat. Among the 4 macrophytes, S. muticum, an invasive species found within the study area, and F. vesiculosus attracted the highest species richness and biomass, which suggests that the co-occurrence of these 2 species (in the absence of space or nutrient competition) results in an important habitat for epibenthic fauna. There was no overall effect of patch size, although within the F. vesiculosus and Z. marina treatments, patch size-dependent variations were found.