ORIGINS OF THE MODERN ANTARCTIC MARINE BIOTA-- PLATE TECTONIC AND OCEANOGRAPHIC RECONFIGURATIONS

The Antarctic marine biota today is surprisingly diverse. It contains algae, protozoans, and metazoans from fish to birds and marine mammals. Although we commonly think of Antarctica as a difficult and hard environment for life, that is obviously incorrect as thousands of species across all branches of life live there without constant struggle. It does, however, apply to humans who die almost immediately if stranded without support in Antarctica. About ~5% of the biota can be traced to deep sea origins, another ~5% by immigration from northern areas, but the rest (~90%) evolved in place on Antarctic shelves. Plate tectonic motions isolated the continent as waterways opened between Antarctica and Australia and South America allowing the development of the circumpolar currents. This not only isolated the biota but also created extreme fluctuations in productivity from very little in the winter to very abundant in the summer to which the preexisting biota either became extinct or adapted in place by utilizing production in the summer and relying on detritus and feces accumulated on the sea floor during the summer. These systems began about 20 mya with these physical conditions surrounding the entire continent, making a single biotic marine province, even including deep under ice shelves. The biota now is confronting warming deep shelf water that transports species from northern latitudes which possess predatory capabilities that could decimate the Antarctic biota we know now.