On the nutrition and metabolism of zooplankton III. Nitrogen excretion byCalanus

Abstract

Nitrogen excretion byCalanus finmarchicus(Gunnerus) andC. helgolandicusClaus collected at Millport and Plymouth has been measured under various experimental conditions.Adult females feeding onBrachiomonas submarina, Cricosphaera elongataandSkeletonema costatumat cell concentrations corresponding to the mean annual level of particulate nitrogen in Plymouth Sound excrete 12·4, 9·0 and 6·4 μg N/mg dry body weight/day respectively. When the concentration of food is raised, as might occur during a spring outburst of phytoplankton, there is an increase in the quantity of nitrogen excreted. On the other hand, nitrogen excretion rapidly diminishes in the absence of food.