Title: THE ROLE OF WATER CHEMISTRY IN CONTROLLING THE
          MERCURY CONCENTRATION OF FISH FROM MARYLAND LAKES

Background
Mercury (Hg) is a contaminant of concern that is known to accumulate in aquatic ecosystems where it has toxic effects on wildlife. Furthermore, humans can be exposed to mercury through the consumption of fish, and currently 39 U.S. states have fish consumption advisories based on Hg concentration. Combustion processes, most notably the burning of fossils fuels and waste incineration, release Hg to the atmosphere. Anthropogenic emissions have increased the amount of Hg in the atmosphere approximately four-fold since the onset of industrialization. Atmospheric deposition of Hg can lead to elevated levels in aquatic organisms in sites remote from direct (point) sources of Hg pollution. Once deposited in water body, a number of complex chemical and biological processes lead to the accumulation of Hg in the food web. As a result, in addition to the amount Hg deposition, a number of factors control the concentration of Hg in fish.

Purpose
The purpose of this study is to address the question: Which is more important in determining the concentration of Hg in fish, the amount of Hg deposition or in-lake chemical and biological processes?

Research objectives

Our objective is to measure the Hg concentration in fish in lakes which receive similar atmospheric loading of Hg, but differ in their water quality. Specifically, we will investigate how two water quality characteristics - pH and dissolved organic carbon content - are related to the concentration of Hg in fish from a number of Maryland lakes.

Educational and scientific impact
This project provides an introduction to a global-scale environmental problem, and it illustrates the complexity of toxicant cycling in the aquatic environment. Participants will get hands-on experience measuring Hg levels in fish tissue. They will process data using spreadsheet software, and data analysis will include graphical and statistical evaluation. The study results will be interpreted in light of how both chemical and food-web interactions control Hg bioaccumulation. Scientific insight gained will include a better understanding of the factors that lead to human exposure to Hg through fish consumption. The results collected here can potentially help managers and policy makers effectively deal with this widespread contaminant.