CONCENTRATIONS OF METALS ASSOCIATED WITH MINING WASTE IN SEDIMENTS, BIOFILM, BENTHIC MACROINVERTEBRATES, AND FISH FROM THE COEUR-DALENE RIVER BASIN, IDAHO

Arsenic, Cd, Cu, Pb, Hg, and Zn were measured in sediments, biofilm, b enthic macroinvertebrates, and fish from the Coeur d'Alene (CDA) River to characterize the pathway of metals transfer between these componen ts. Metals enter the CDA Basin via tributaries where mining activities have occurred. In general, the ranking of food-web components from th e greatest to smallest concentrations of metals was as follows: biofil m (the layer of abiotic and biotic material on rock surfaces) and sedi ments > invertebrates > whole fish. Elevated Pb was documented in inve rtebrates, and elevated Cd and Zn were documented in sediment and biof ilm approximately 80 km; downstream to the Spokane River. The accumula tion of metals in invertebrates was dependent on functional feeding gr oup and shredders-scrapers that feed on biofilm accumulated the larges t concentrations of metals. Although the absolute concentrations of me tals were the largest in biofilm and sediments, the metals have accumu lated in fish approximately 50 km downstream from Kellogg, near the to wn of Harrison. While metals do not biomagnify between trophic levels, the metals in the CDA Basin are bioavailable and do biotransfer. Trou t less than 100 mm long feed exclusively on small invertebrates, and s mall invertebrates accumulate greater concentrations of metals than la rge invertebrates. Therefore, early-lifestage fish may be exposed to a larger dose of metals than adults.