Description of Work U.S. Geological Survey (USGS) scientists are improving the health of the Great Lakes sport and commercial fisheries by documenting sources and the determining the processes that control mercury entering food webs, and helping to evaluate the implications for public health. Our scientists will provide decision-makers with a scientific understanding of mercury-source profiles, the relative importance of the various sources, and the expected environmental responses to Great Lakes wasters and fisheries to altered mercury loading and restoration actions. This information is intended to inform and maximize the benefit of the Great Lakes restoration program. The USGS will develop mercury and methylmercury mass budgets [...]