Mercury Accumulation in Fish and Invertebrates of the North Fork Holston River, Virginia and Tennessee

Abstract

AbstractWe investigated both total and methylmercury accumulation in fish and invertebrates in the North Fork of the Holston River below a currently inactive chloralkali plant (i) to quantify the extent of contamination, (ii) to determine what proportion of the variance in mercury concentration in fish can be explained by mercury concentration in water, sediment, benthic invertebrates, and (iii) to determine what proportion of mercury concentration in benthic invertebrates can be explained by mercury concentration in water and sediment. Fish species [rock bass (Ambloplites rupestris) and hog sucker (Hypentelium nigricans)] and benthic invertebrates were collected from stations above and below the plant, and axial muscle (fish) or whole animal (invertebrates) was analyzed for total mercury by flameless atomic absorption and for methylmercury by gas chromatography. The relation of total mercury concentration to fish weight and factors affecting mercury concentration in fish and invertebrates were examined through regression analysis.Total mercury concentration in fish and benthic invertebrates decreased with distance below the plant. Significant linear regressions of total mercury concentration on fish weight were observed for some, but not all, samples examined. Mercury in the methyl form comprised 91.7% of total mercury in fish analyzed, while approximately 50% of the mercury in invertebrates was methylmercury.Multiple regression analysis indicated 96.4% of the variance in total mercury concentration in rock bass and 80.5% in hog suckers was accounted for by mercury in water, sediment, and benthic invertebrates. Independent variables accounted for 97.4% of the variance in total mercury concentration in benthic invertebrates. The potential implication of these results for environmental monitoring programs is discussed.