Macronutrients in the Summer Sea ice of the Ross Sea.

The development and production of sea ice microbial communities is often linked to limitations imposed by light, temperature and salinity. Nutrients also impose a limitation upon biomass development and production. Nutrient constraints on biomass development was readily evident in surface habitats of the pack ice of the Ross Sea during the summer of 1999. The spatial extent of nutrient depletions, primary production and biomass accumulation- investigated at both large (100s of kilometers) and small (centimeter to meter) scales- showed the importance of the tight coupling between the ice cover's gross morphological features (e.g. brine tubes, cracks and floes size) in determining the extent to which extremely productive communities developed. Specifically, extreme nutrient depletions were often observed in areas where brine tubes or cracks were not readily apparent, whereas, relatively enhanced nutrients and large biomass accumulations (exceeding 50 to 1000+ ug Chla per liter) were often found in association with the floe edges, cracks and brine tubes. These features and links were documented over the entire latitudinal extent of the summer pack ice (January of 1999)- yet, were especially apparent in the southern region. Whether or not these features and the tight coupling observed are a ubiquitous and common feature of the late spring and summer pack ice of the entire Southern Ocean remains to be determined.