Heavy metals in the threeridge mussel Amblema plicata plicata (Say, 1817) in the upper Mississippi River

Concentrations of mercury and zinc in the threeridge mussel Amblema plicata plicata, sampled in 1987 from Pools 3 and 10 in the upper Mississippi River, were comparable to concentrations in mussels from moderately contaminated systems, while copper concentrations were similar to concentrations in mussels from more polluted waters. Cadmium concentrations in mussels were significantly less at a lightly contaminated site (Pool 10, range 0.53 to 0.92 mu g/g dry weight) than at a site where metal abundances were strongly influenced by industrial and domestic inputs (Pool 3, range 0.80 to 1.25 mu g/g dry weight). Yet, cadmium concentrations in Pool 3 were an order of magnitude less than values reported for mussels from more metal-polluted systems. In contrast, concentrations of copper, mercury, and zinc did not differ between sites. Cadmium and zinc concentrations generally increased with size of the mussel, copper concentrations decreased with size, and mercury concentrations were unrelated to size.a