Distribution patterns in Antarctic and Subantarctic echinoderms

Abstract

Echinoderms are the dominant megafaunal taxa in Antarctic and Subantarctic waters in terms of abundance and diversity, having a predominant role in structuring communities. The current study presents new data on the asteroids, holothuroids, and ophiuroids (three of the five extant classes of echinoderms) collected in seven scientific campaigns (1995–2012) from Bouvet Is., South Shetland Is., and the Eastern Weddell Sea, from a wide bathymetric range (0–1,525 m). Among the 316 echinoderms collected, we extended the bathymetric ranges of 15 species and expanded the geographic distribution of 36 of them. This novel dataset was analyzed together with previous reports in order to establish general patterns of geographic and bathymetric distribution in echinoderms of the Southern Ocean (SO). Nearly 57 % of the assembled-data species resulted endemic of the SO, although further taxonomic efforts in less accessible areas are needed. Interestingly, some islands presented high levels of species richness even comparable to large geographic areas. While generally exhibiting a wide range of eurybathy, there were differences in species composition across depths corresponding to sublittoral, upper and lower bathyal, and abyssal. Bathymetric distribution was analyzed considering biological aspects for each class. As expected, circumpolar trends were found, although hydrographic currents may be the cause of differences in species composition among SO areas. Our analyses suggest zoogeographic links between Antarctica and the adjacent ocean basins, being the Scotia Arc the most remarkable. This study contributes to the knowledge of large-scale diversity and distribution patterns in an Antarctic key group.