Mysids and trace metals: disruption of swimming as a behavioural indicator of environmental contamination.

Mysids are used frequently in standard laboratory studies of acute exposure to chemical contaminants. Their value for sub-lethal measures of biological response to predict the potential effects of environmental toxicants, however, has yet to be determined. In estuaries, mysids maintain their optimum position independent of the forces of river flow and tides; therefore, any disruption of swimming behaviour will have significant implications for their survival and position maintenance. In the present study, the effects of cadmium on the swimming behaviour of the hyperbenthic estuarine mysid Neomysis integer, which occupies the heads of European estuaries, are presented. Following 7 day exposure to cadmium, swimming behaviour (ability and orientation) was disrupted at 0.5 microgram Cd(aq)2+ l-1, a significantly lower cadmium concentration than that causing mortality (7 day LC50 of 2.58 micrograms Cd(aq)2+ l-1). The results of this investigation highlight the advantages of behavioural toxicity tests for predicting the influence of pollutants and support the use of mysids for estuarine monitoring.