Evolution and diversity of the benthic fauna of the Southern Ocean continental shelf

Abstract

The modern benthic fauna of the Antarctic continental shelf is characterized by the lack of active, skeleton-breaking (durophagous) predators such as crabs, lobsters and many fish, and the dominance in many areas of epifaunal suspension feeders. It has often been remarked that these ecological characteristics give the fauna a distinctly Palaeozoic feel, with the assumption that it may be an evolutionary relic. We now know that this is not so, and fossil evidence shows clearly that many of the taxa and life-styles that are absent now were previously present. The modern fauna has been shaped by a number of factors, important among which have been oceanographic changes and the onset of Cenozoic glaciation. Sea-water cooling, and periodic fragmentation of ranges and bathymetric shifts in distribution driven by variability in the size and extent of the continental ice cap on Milankovitch frequencies will all have caused both extinction and allopatric speciation. The modern glacial setting with relatively low terrestrial impact away from immediate coastal regions, and scouring by icebergs are the key factors influencing the ecology and population dynamics for the modern Antarctic benthos.