Summer plankton production and nutrient consumption patterns in the Mertz Glacier Region of East Antarctica

Abstract

Abstract We report on a biological and nutrient survey conducted off the eastern Adelie and George V Coasts of East Antarctica in late December 2000 and January 2001. The region was dominated by the Mertz Glacier Tongue (MGT) and its associated polynya that controlled the amount of open water through the season and influenced stratification near forming and melting ice. As in other regions of the Southern Ocean, large concentrations of nitrate, phosphate and silicic acid were found. Chlorophyll levels varied from 0.3 mg m−3 in pack-ice and slope regions to greater than 10 mg m−3 in a Phaeocystis bloom encountered among grounded ice northeast of the MGT. Net utilization rates of nutrients were derived from the deficit between measured concentrations and estimated winter values. Nitrate (N+N) and silicic acid utilization rates ranged from 2 to 12 and 14 to 30 mmol m−2 d−1, respectively, and were greatest in Commonwealth Bay. The ratio of nitrate to phosphate utilization was low ( 10. Lower silicic acid to N+N ratios were found in regions with substantial populations of Phaeocystis sp. in the eastern, grounded ice region. However, there was significant variation in the silicic acid to N+N utilization that may be induced by mixed-layer iron levels that varied from