Abundance and size patterns of echinoderms in coastal soft-bottoms at Deception Island (South Shetland Islands, Antarctica)

- High sedimentation rates favor high abundances of echinoderms.
- Filter-feeders shallow soft-bottom benthic communities were absent at DI.
- Depth-related factors play a pivotal role structuring the macrobenthic communities
- Size-gradient in the densities of echinoderms inhabiting the subtidal zones

Deception Island is an active volcano in Antarctic waters under high sedimentation regimes, which may affect the abundance and structure of soft-bottom assemblages. During the summer of 2012-2013, a survey of the shallow water soft-bottom assemblages of Deception Island was carried out to examine patterns of abundance and size structure of the three dominant echinoderms (Ophionotus victoriae, Sterechinus neumayeri and Odontaster validus) at 8 locations encompassing a gradient in proximity from the open ocean, including two depths (5 vs. 15 m) per location. Abundance patterns of the three species varied with depth; organisms were typically more abundant at 15 relative to 5 m depth. Our results partially supported the hypothesis that echinoderms from locations adjacent to the open ocean present larger abundances. Body sizes varied significantly among locations and depths for the three species and some places presented a density-size pattern. High sedimentation rates, combined with low ice-related disturbance, may be the reason behind the large abundances of echinoderms found in this waters.