Changing chain: past, present and future of the Scotia Arc’s and Antarctica’s shallow benthic communities

The Scotia Arc links Patagonia to the Antarctic Peninsula. This island chain has changed considerably since Antarctica’s geographic and thermal isolation from other land and water masses. Now its rates of air, land and fresh-water climate change are among the highest measured. This review examines work on the shallow water benthos of this region in the context of climate change. In summer, primary productivity is as intense as anywhere, whilst in winter the water reaches unprecedented clarity. Suspension feeders may eat for just a few months but others feed all year. Growth and reproduction are up to 50x slower than non-polar rates. Life here is in the slow lane. There is intense summer disturbance from ice-scour and wave action. This has erased shore zonation and created it below the surface. In contrast to summer disturbance, the winter is among the calmest and most thermally stable environments, when the area is overlain by fast ice. Whilst few animal phyla or species are represented on land, phyletic richness—and in some groups species richness—rivals that of tropical regions. Data showing clines in benthic richness at several taxonomic levels across the Patagonia-South Georgia-Signy Is.-Adelaide Is. chain and 50 years of ice-sheet retreat are presented.

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