Statement of Problem: A recent USGS study (3110BG4.22) reported comparatively high concentrations of mercury (Hg) in smallmouth bass collected from waters of the Ozark National Scenic Riverways and other recreationally significant rivers in southern Missouri. The findings of this study corroborated historical data; i.e., most legal-sized fish contained sufficient Hg to warrant restriction to <2 meals/month based on current USEPA recommendations. However, and in contrast to expectations, concentrations differed substantially among the locations sampled, as did the relations between Hg concentrations and fish size/age. The study described here is designed to investigate potential reasons for the differing Hg concentrations reported by the previous study through the analyses of additional samples from previous studies for Hg; stable isotopes of nitrogen, carbon, and sulfur; biological variables related to the nutritional status of the fish; and historical water quality data.
Objectives: The objectives of this investigation are to (1) better define the extent of Hg contamination in stream ecosystems of southern Missouri, and (2) to investigate factors that may control or influence the fate of Hg in these streams through analysis of biota (fishes and invertebrates) for stable isotopes of nitrogen (N), carbon (C), and sulfur (S), and of other variables defining the nutritional status and growth histories of the fish.