Epibenthic communities' structure in St. Pierre Bank revealed by underwater video

Abstract

Given the significant ecosystem services provided by benthic communities, monitoring their biodiversity enable to better understand how global changes would affect their structure in a context of biodiversity loss. Using underwater video transect, we characterize alpha and beta diversity of epibenthic communities, their structure and forcing factors in St. Pierre Bank; an area where marine benthos is still poorly documented. Video monitoring enables the detection of 74 different taxa belonging to eight phyla. Results highlighted three spatial entities of benthic assemblages distributed along a bathymetric gradient and primarily influenced by sedimentary types. In the southern and western area, rhodoliths beds substrate shelters the majority of echinoderms. The southern region was dominated by sea cucumber Cucumaria frondosa, whereas in the western area, brittle stars, and the green sea urchin Strongylocentrotus droebachiensis were dominant. Fishing activity was concentrated in the south, due to the presence of exploited sea cucumber. In contrast, the northern region featured patchy fine and soft substrates with a preponderance of giant scallop Placopecten magellanicus and sand dollar Echinarachnius parma. In addition to the contribution of environmental factors to the distribution of communities, this study highlights the complexity of several biotic interactions at the origin of these assemblages.