Abstract:

Metabolic rates (oxygen consumption and ammonia excretion) of two dominating copepods, Calanoides acutus and Metridia gerlachei , were measured during the austral summer (December 1998-January 1999), in the marginal ice zone of the Prydz Bay. The elemental composition (C and N) were also analysed on the specimens used in these metabolic experiments. The results showed that C. acutus was 48.4%-48.6% of dry weight in carbon content and 6.1%-6.5% of dry weight in nitrogen content. Metridia gerlachei was 47.1%-50.1% and 5.9%-7.4%, relatively. Oxygen consumption rates of C. acutus were variant in the different areas (0.226 to 0.558μl O 2mg -1 h -1 ). And its ammonia excretion rates ranged from 0.014 to 1.058μg N mg -1 h -1 . The ratio between the rates (O∶N) exhibited a large defference(5-6 times). For Metridia gerlachei , oxygen consumption rates were 0.488-0.644μl O 2mg -1 h -1 and ammonia excretion rates were 0.015-0.034μg N mg -1 h -1 . From the results of metabolic rate measuremts and elemental analyses, daily losses of body carbon and nitrogen were estimated to be 0.59% - 1.99% and 0.44% - 3.27%, respectively. The metabolic carbon requirements represented about 0.6%-29.2% of primary production per day, and their excretion of ammonia contributed 0.2%-38.0% of daily phytoplankton nitrogen demand.