ASSEMBLAGES OF SEA STARS (ECHINODERMATA, ASTEROIDEA) AND BRITTLE STARS (ECHINODERMATA, OPHIUROIDEA) IN THE WEDDELL SEA (ANTARCTICA) AND OFFNORTHEAST GREENLAND (ARCTIC) - A COMPARISON OF DIVERSITY AND ABUNDANCE

Composition and distribution of asteroid and ophiuroid assemblages wer e investigated by means of Agassiz trawl catches at 34 stations in 220 - to 1,200-m depth in the Weddell Sea and at 17 stations in 90- and 83 0-m depth off Northeast Greenland. A total of 86 species (48 sea stars , 38 brittle stars) were identified in the Weddell Sea whereas off Nor theast Greenland a total of 26 species (16 sea stars, 10 brittle stars ) were recorded. In both study areas, brittle stars were numerically m ore important than sea stars, and abundances generally decreased with water depths. Multivariate analyses revealed a conspicuous depth zonat ion of sea and brittle stars off Greenland. Very high abundances of Op hiocten sericeum and Ophiura robusta characterized the assemblages on shallow shelf banks whereas in greater depths Ophiopleura borealis, Op hioscolex glacialis and Ophiacantha bidentata became dominant, albeit at significantly lower densities. Mass occurrences of brittle stars, s uch as those recorded on Greenlandic shelf banks, have not been discov ered in the Weddell Sea, where distinct assemblages were discriminated in deep shelf trenches as well as on the eastern and southern shelf. Ophioplocus incipiens, Ophiurolepis martensi and Ophiurolepis brevirim a were the most prominent species on the eastern shelf, Ophiacantha an tarctica, Ophiurolepis gelida and Ophionotus victoriae on the southern shelf, and Ophiosparte gigas, as well as the asteroid Hymenaster sp., in the shelf trenches. Overall, the Weddell Sea housed conspicuously more asterozoan species than the waters off Greenland. Higher species diversity was also evident at both a regional and local scale, especia lly for the eastern Weddell Sea shelf. However, because many species f rom the Weddell Sea are closely related, the Weddell Sea assemblages w ere not significantly different from the Greenland ones in terms of ta xonomic diversity and distinctness.