Cadmium incorporation by the marine copepod Pseudodiaptomus coronatus1

Abstract

Pseudodiaptomus coronatus, after exposure to phytoplankton and cadmium in concentrations like those in temperate, coastal environments, incorporated 109Cd at higher rates from ambient water than from phytoplankton food. When ambient stable cadmium concentrations were increased from 0.03 to 1.00 µg·liter−1, cadmium concentration by phytoplankton cells increased and the rate of cell ingestion by P. coronatus decreased. This inverse relation between the accumulation of cadmium in phytoplankton cells and the animal’s ingestion rate resulted in relatively small net increases in the cadmium accumulated from phytoplankton by copepods.Rates of stable cadmium ingestion for P. coronatus ranged from 0.18 to 0.38 ng·mg animal dry wt−1·h−1, depending on the initial algal cell density and the ambient cadmium concentration. For cadmium concentrations of 0.03 to 1.00 µg·liter−1, percentage assimilation efficiencies ranged from 13.20 to 68.40. Both rates of cadmium ingestion and assimilation efficiencies were higher than published values for carnivorous zooplankton.