Probing the depths

Abstract

When scientists from HMS Challenger dredged animals from over 5km depth, they finally laid to rest the azoic hypothesis of Edward Forbes, that life could not exist in cold dark depths of the ocean, and thereby opened the doors to true deep-sea biology. The past decade has witnessed a further sea change in our view of marine diversity, if I may be permitted the pun, a change driven to a large extent by improved knowledge from Antarctica. For many years we viewed the tropics as the engines of diversity; species arose in warm clear seas, especially those associated with coral reefs, and spread slowly to populate the harsher high latitudes. Early studies of the isopod fauna had also suggested that at least some organisms living on the continental shelf of Antarctica may have originated in the deep sea. After a period of intense work, much of it under the auspices of the SCAR EASIZ (Ecology of the Antarctic Sea Ice Zone) and more recently the EVOLANTA(Evolution in Antarctica) programmes, we can now modify both hypotheses, with powerful implications for our understanding of global marine diversity. The marine invertebrate fauna of the Antarctic continental shelf is now better described than might be thought, and the total fauna may well exceed 17000 taxa. Interestingly, there are very few places in the world with comparable data, but we can say that the fauna has had a long history of evolution in situ and is not simply a last refuge for taxa that originated elsewhere.