Infaunal polychaete communities from the Antarctic Peninsula and the Filchner Trough region (Weddell Sea)

Polychaetes are a dominant and functionally diverse infaunal group of marine soft-bottom ecosystems. Yet their biodiversity and community composition remain poorly understood in the Weddell Sea (WS). We investigated the composition of polychaete communities (taxonomic and functional identity) in two key regions of the WS (Antarctic Peninsula and Filchner Trough region). Sediment cores collected during three RV Polarstern expeditions (PS81, 96, 118), revealed 1,605 polychaete individuals from 34 families. We assigned them into 14 functional groups, based on their feeding, motility and movement type. Polychaete abundances were highest in the northwestern WS and lowest at the deeper Filchner Trough sites, while the number of taxa was similar in all regions. Cluster analyses distinguished six taxonomic and five functional community types, indicating heterogeneous community structures. Paraonidae and Cirratulidae were the dominant families. Motile borrowing subsurface deposit feeders prevailed functionally across sites. Regional differences were e.g., that Hesionidae, Opheliidae and Maldanidae were more abundant around the Antarctic Peninsula, Syllidae, Glyceridae and Lumbrineridae in the Filchner Trough region. Our results highlight the spatial variation of polychaete communities and emphasize the need to integrate taxonomic and functional perspectives to comprehensively assess the different facets of biodiversity and to support conservation efforts for vulnerable WS regions.