Meeting Abstract

S7.2  Tuesday, Jan. 5  Marine Microalgae in Antarctic Sea Ice ARRIGO, K.R.; Stanford University arrigo@stanford.edu

Antarctic sea ice is often home to a rich microbial community, generally dominated by microalgae such as diatoms. These organisms have unique adaptations that allow them to grow at the low light, reduced temperatures, and high salinities that characterize the sea ice interior. Nevertheless, these microbial communities develop to their full potential in sea ice that has little snow cover and is relatively warm. Under these conditions, the sea ice environment receives considerable light and has a brine salinity that is sufficiently low to facilitate rapid algal growth. Consequently, the highest algal biomass is often attained in the austral spring just before the ice has begun to melt. Because these communities are often so concentrated, they represent a valuable food source for larger organisms that both live within the ice and enter the ice from the water column through the myriad cracks and brine tubes that characterize the ice pack. They also become a rich source of food when they are released from the ice matrix as the ice begins to melt. As this material sinks through the water column, some is consumed by pelagic zooplankton and the rest sinks to the bottom where it nourishes a diverse benthic community. In areas with annual ice cover, the productivity within the ice can represent a large fraction of total production, the rest being contributed by pelagic phytoplankton. Unfortunately, to date, there are few comprehensive estimates of total sea ice algal production within the Antarctic ice pack, due to the fact that direct measurements are so sparse. Those estimates that do exist are based on a limited number of modeling studies and suggest that total productivity within Antarctic sea ice is probably less than 100 Tg C/yr. Although this is a small fraction of total production in the Southern Ocean, it can represent a locally important carbon source.