NOTES ON THE BIOLOGY OF SEA-ICE IN THE ARCTIC AND ANTARCTIC

The sea ice which covers large areas of the polar regions plays a majo r role in the marine ecosystem of both the Arctic and Southern Oceans. Not only do warmblooded animals depend on sea ice as a platform, but the sympagic organisms living internally within the sea ice or at the interfaces ice/snow and ice/water provide a substantial part of the to tal primary production of the ice covered regions. In addition sea ice organisms are an important food source for a variety of pelagic anima ls and may initiate phytoplankton spring blooms after ice melt by seed ing effects. Sea ice organisms often are enriched by some orders of ma gnitude if the same volume of melted ice is compared to that of the un derlying water column. Three hypotheses try to explain this discrepanc y and are discussed. Investigations on the nutrient chemistry within t he sea ice system and in-situ observations still are rare. Intense gro wth of sympagic organisms can result in nutrient deficiencies, at leas t in selected habitats. Advances in endoscopic methods may lead to a b etter understanding of the life within the sea ice.