Southern Ocean Deep Benthic Biodiversity

The deep sea is the largest environment on the planet, the least well known and one of the least studied. It contains extremely large habitats, and millions of km2 of continental slopes and abyssal plains. These incorporate other geological structures, including canyons, seamounts, reefs, hydrothermal vents, mud volcanoes, and faults at active and passive margins, which support unique microbiological and faunal communities. Despite our limited knowledge of deep-sea biodiversity, we now know that the Southern Ocean (SO) deep sea is very speciose within many taxa, and it is therefore likely that more species occur in the deep sea than any other biome on earth (Gage&Tyler, 1991). In many taxa far more than 90% of the species collected in a typical abyssal sediment sample are new to science, and usually H 50% of these appear to be rare (Glover et al., 2002; Brandt et al., 2007a–c; Ellingsen et al., 2007; Smith et al., 2008). Some authors have demonstrated that the occurrence of rare species in samples is the result of sampling the regional fauna only (Rex et al., 2005b). However, analyses comparing abundance across different spatial scales in SO deepsea isopods have revealed high biological variability, which indicates patchiness rather than rarity, of most isopod taxa (Kaiser et al., 2007).