Habitat-Specific Differences in Mercury Concentration in a Top Predator from a Shallow Lake

Abstract

We conducted a survey of mercury contamination in largemouth bass Micropterus salmoides from Caddo Lake, Texas, and found that fish collected from forested wetland habitat had higher concentrations of mercury than those collected from open-water habitat. Habitat-specific differences in largemouth bass size, age, absolute growth rate, trophic position (based on d15N), and horizontal food web position (based on d13C), characteristics known to influence mercury accumulation, did not explain the observed differences in mercury contamination. Rather, habitat-related differences in mercury concentration in a primary consumer, Mississippi grass shrimp Palaemonetes kadiakensis, indicated that food webs in forested wetland habitat were more contaminated with mercury than those in open-water habitat. Spatial variation in mercury contamination within lakes and elevated mercury concentrations in forested wetlands should be of special concern not only to researchers but also to public and environmental health officials dealing with mercury contamination in aquatic environments and human health risks associated with consumption of fish contaminated with mercury.