BIOACCUMULATION OF MERCURY IN LARGEMOUTH BASS FROM NORTHWESTERN MISSOURI

Mercury (Hg) is a global pollutant that arises from the burning of fossil fuels and other anthropogenic events as well as the volatilization of natural Hg pools. Hg is methylated by sulfur reducing bacteria in anaerobic aquatic environments and is bioaccumulated in fish. The bioaccumulation of Hg in fish has led to the development of fish advisories across the United States. These advisories recommend people limit their consumption of specific fish species from certain bodies of water as a result of chemical pollutants. This is particularly important for pregnant women, women of reproductive age and children under the age of 13. Over the last two years we have reported Hg concentrations for the following fish species: blue catfish (Ictalurus furcatus), longnose gar (Lepisosteus osseus), flathead catfish (Pylodictis olivaris), largemouth bass (Micropterus salmoides), channel catfish (Ictalurus punctatus) and freshwater drum (Aplodinotus grunniens).

The present study investigates the bioaccumulation of Hg in largemouth bass from eight farm ponds in Daviess County, Missouri (MO), a non-urban agricultural area. Water, soil and pond core samples were also collected to test Hg concentrations. The purpose of this sampling was to understand the biogeochemical cycling of mercury within the environment, leading to the bioaccumulation of mercury in fish (e.g., largemouth bass). We hypothesized this top predator was thought to bioaccumulate more Hg than other fish previously studied (Dilek et al. 2014; Morgan et al.2013).

Hg concentrations (ng/g) in largemouth bass (lengths 6-15 in., n>50) ranged from 10 to 520 ng/g. In 2014, largemouth bass (lengths 6-12 in, n>10) Hg concentrations ranged from 250 to 480 ng/g. Increases in length correlated with increases in Hg concentration. High fish Hg concentrations may be attributed to sulfur reducing bacteria present in the ponds and rivers of MO. Bacteria sequester Hg pollutants and transfer the Hg to fish. We hypothesized that concentrations of sulfur in the farm ponds would be correlated with Hg concentrations concentrations in largemouth bass. As in previous studies large fish often exceed the EPA guidelines and caution should be exercised in the consumption of largemouth bass greater than ten inches in length.