Cadmium, Metal-binding Proteins, and Growth in Bluegill (Lepomis macrochirus) Exposed to Contaminated Sediments from the Upper Mississippi River Basin

We exposed juvenile bluegill (Lepomis macrochirus) to ~1000 mg∙L−1 of continuously suspended river sediment in a 28-d test with six treatments (randomized block with one sediment-free control and five sediments ranging from 1.3 to 21.4 μg Cd∙g dry weight−1). Each treatment had three replicates, each with 25 fish. Growth was reduced by exposure to suspended sediment, probably due to physical effects of sediment on feeding and to toxicity in the treatment with the greatest concentrations of metals. Mean whole-body concentrations of cadmium (0.04–0.14 μg∙g wet weight−1) were correlated with cadmium concentration in filtered water (8–72 ng∙L−1), suspended sediment (0.61–16.8 μg∙L−1), and bulk sediment. The concentration of hepatic nonthionein cytosolic cadmium (cadmium not bound by metal-binding proteins, MBP) in fish exposed to the two most contaminated sediments exceeded that in controls. The mean concentration of hepatic MBP was correlated with cadmium concentration in filtered water, suspended sediment, bulk sediment, and whole fish. Whole-body cadmium concentration was the most sensitive indicator of cadmium exposure, with lowest observed effect concentrations of 1.9 μg Cd∙L−1 for suspended sediment and 13 ng Cd∙L−1 for filtered water. Sediment-associated cadmium was less available than waterborne cadmium for uptake by fish.