Global Climate Change and the Origin of Modern Benthic Communities in Antarctica

Abstract

Marine benthic communities living in shallow-water habitats (<100 m depth) in Antarctica possess characteristics reminiscent of Paleozoic marine communities and modern deep-sea communities. The absence of crabs and sharks, the limited diversity of teleosts and skates, the dominance of slow-moving invertebrates at higher trophic levels, and the occurrence of dense ophiuroid and crinoid populations indicate that skeleton-breaking predation is limited in Antarctica today, as it was worldwide during the Paleozoic and as it is in the deep sea today. The community structure of the antarctic benthos has its evolutionary roots in the Eocene. Data from fossil assemblages at Seymour Island, Antarctic Peninsula suggest that shallow-water communities were similar to communities at lower latitudes until they were affected by global cooling, which accelerated in the late Eocene to early Oligocene. That long-term cooling trend ultimately resulted in the polar climate and peculiar community structure found in Antarctica today. Declining temperatures beginning late in the Eocene are associated with the disappearance of crabs, sharks, and most teleosts. The sudden drop in predation pressure allowed dense ophiuroid and crinoid populations to appear and flourish. These late Eocene echinoderm populations exhibit low frequencies of sublethal damage (regenerating arms), demonstrating that there was little or no predation from skeleton-breaking fish and decapods. Current scenarios of global climate change include predictions of increased upwelling and consequent cooling in temperate and subtropical upwelling zones. Limited ecological evidence suggests that such cooling could disrupt trophic relationships and favor retrograde community structures in those local areas.