The occurrence of cadmium, copper, lead, and zinc in macroinvertebrates of the Fox River, Illinois
Anderson, Richard V.
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The concentrations of cadmium, copper, lead and zinc in aquatic macroinvertebrates from four sampling sites were at Waterford, Wisconsin Algonquin, Elgin, and Geneva, Illinois. The sites represent varying degrees of potential input of the studied trace metals. It was found that the macroinvertebrates from sites receiving heavy input from urban and industrial areas had the highest concentrations of the metals cadmium and lead. For example Hydropsyche cadmium and lead concentrations at Geneva were 3.19 ?g/g and 18.24 ?g/g respectively compared to cadmium 0.53 ?g/g and lead 4.99 ?g/g at Algonquin. Consequently macroinvertebrates could be used to monitor trace metal input providing areas of both high and low input with similar taxa were sampled. Copper and zinc, which are physiologically important in some invertebrates, were found to have concentrations which were relatively consistent at all the sampling sites despite variation in potential input. In crayfish copper concentrations were approximately 70 ?g/g at all sampling sites. Thus, for metals with physiological roles, the invertebrates show regulatory ability in both intake of the metals and elimination of excess body burdens of the metals. No significant accumulation up the food chain was found for any of the studied trace metals. Substrate and detrital feeders were found to have higher concentrations of the trace metals than organisms whose diet was primarily animal material. It was found that metal concentration will vary depending on the life cycle stage or instar an organism is in since feeding activity, food selection, and exoskeleton condition vary relative to the time of year and size of the organism. There was an inverse relationship between metal concentration and the weight of the organisms. Analysis of crayfish tissue showed areas of concentration of the trace metals in the body. Lead was found in significantly higher concentration in the exoskeleton, 25 ?g/g dry weight of tissue, and gills, 20 ?g/g, than in viscera and muscle, 7 ?g/g. The accumulation of Pb in the exoskeleton is judged to be due to the method of arthropod integument formation and the exoskeleton acts as a sink for lead. High cadmium concentrations were found in the gills and viscera, a result of adsorption and absorption on surface areas. The concentration of physiologically important copper was related to the amount of hemocyanin present in a particular body area as well as the presence of copper storage sites. Thus, crayfish gills and viscera had relatively high copper concentrations, approximately 110 ?g/g dry weight of tissue, compared to 14 yg/g in the exoskeleton which has a low blood volume. Zinc was found in approximately equal concentrations in gills, viscera, and muscle. Significantly lower zinc concentrations were found in the exoskeleton. While there was a considerable variation in the range of concentrations found, the general relationship between the metals concentrations was Cd<Pb?Cu<Zn. This generally reflects environmental metal relationships at all sites.