Assimilation of metals in marine copepods and its biogeochemical implications

Assessed the retention efficiency of ingested metals in the calanoid copepod Anomalocera patersoni and the retention of excreted metals in fecal pellets. Adult copepods ingested the haptophyte Isochrysis galbana labeled with ¹⁰⁹Cd, ⁶⁵Zn, ²⁰³Hg, ²⁴¹Am and ²³⁷Pu at a rate of 3.79 mg algal C g^-1 animal dry wt h^-1. Average retention efficiencies were 30% for Cd, 48% for Zn, 21% for Hg, 4.5% for Am, and 0.8% for Pu. The fecal pellets produced by animals feeding on radioactive I. galbana lost essentially all of their ¹⁰⁹Cd, ⁶⁵Zn, ²⁴¹Am, and ²³⁷Pu to unlabeled seawater within 1-d. ²⁰³Hg was lost most slowly; its retention half time was about 25-d in the slowly exchanging pool. Retention efficiencies suggest that Cd, Zn, and Hg should be recycled by copepods in surface waters as part of the organic cycle in the sea, while the transuranic element should be defecated and removed from surface waters by sinking biogenic debris. -from Authors