Study on the metabolism of two dominant copepods: Calanoides acutus and Metridia gerlachei collected in summer from the marginal ice zone of the Prydz Bay, Antarctica

Metabolic rates (oxygen consumption and ammonia excretion) of two dominant 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. Their elemental compositions (C and N) were also analysed through 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 0.774 μlO2mg-1h-1). And its ammonia excretion rates ranged from 0.014 to 0.105 μgNmg-1h-1. The ratio between the rates (O∶N) exhibited a large difference(5 6 times). For Metridia gerlachei, oxygen consumption rates were 0.488 0.644 μlO2mg-1 and ammonia excretion rates were 0.015 0.034 μgNmg-1h-1. From the results of metabolic rate measurements 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 accounted for 0.6% 29.2% of primary production per day, and their excretion of ammonia occupied 0.2% 38.0% of daily phytoplankton nitrogen demand.