| Summary: | Species diversity and distribution -in relation with biogeography, bathymetry and environmental characteristics- within the genus Acantholaimus were investigated on the shelf and slope (182-2,009 m) in the Weddell Sea (Kapp Norvegia and Vestkapp) and near the Antarctic Peninsula (Drake Passage and Bransfield Strait). The occurrence of the otherwise typical deep-sea genus Acantholaimus in high densities and diversity on the continental shelf is a unique feature of the Southern Ocean. Fifty-five Acantholaimus species (morpho-types) were distinguished in our study area, of which 39 were found on the shelf. The Acantholaimus communities were characterised by a high number of congeneric species and the presence of many rare species, similar to typical deep-sea communities. Fourteen species had a distribution extending from the shelf to the lower slope. High local and regional diversity was obvious and a considerable level of endemism was suggested. A negative impact of chlorophyll a concentrations, reflecting the availability of phytoplankton, was found on the Acantholaimus densities and species diversity.
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