Scotia Arc deep-water bivalves: composition, distribution and relationship to the Antarctic shelf fauna

Agassiz trawl, epibenthic sledge and large box core samples were made in the Scotia and northern Weddell Seas during the 2002 ANDEEP expeditions with R.V. Polarstern at 21 locations (774–6348 m depth). The deep-water bivalve fauna sampled was species rich; in total 40 species of bivalves belonging to 17 families were found. At least seven of these species are new to science. Per location species richness varied from 5 to 15 species. Kelliella sirenkoi was the most common and abundant species, occurring at 17 locations (1121–6348 m), followed by Genaxius sp.1 occurring at 12 locations. The epibenthic sledge hauls were characterised by low abundances, varying from 1 to 68 individuals 1000 m−2 in depths greater than 1000 m. In comparison with the shelf fauna of the Scotia Arc, the deep-water bivalve community showed similar species richness. This indicates that there is no diversity cline with depth in Antarctic bivalves, but it does provide evidence for underestimated species richness in deep water because of lack of sampling.