Factors affecting mercury contamination in fish from Caddo Lake, Texas.

Abstract

We conducted a survey of mercury contamination in largemouth bass ( Micropterus salmoides) from Caddo Lake, Texas, and found that largemouth bass collected from forested wetland habitats had higher concentrations of mercury relative to largemouth bass collected from open water habitats. Habitat-specific differences in largemouth bass size, age, growth rate, trophic position (based on delta15N), and horizontal food web position (based on delta 13C), characteristics known to influence mercury accumulation, did not explain the observed differences in mercury contamination. Rather, differences in mercury concentrations in a primary consumer, grass shrimp (Palaemonetes kadiakensis) across the two habitat types indicated that food webs in forested wetland habitats may be more contaminated with mercury. Spatial variation in mercury contamination within lakes and elevated mercury levels in forested wetlands should be of special concern, not only to researchers, but to public and environmental health officials dealing with mercury contamination in aquatic environments and human health risks associated with consumption of mercury-laden fish.