Twin Cities WRS Seminar

Identifying the Cause of High Mercury Levels in Fish from N. Minnesota Rivers


Bruce Monson
Minnesota Pollution Control Agency

September 29, 2017


To reduce mercury in fish, Minnesota’s Statewide Mercury Total Maximum Daily Load study set a goal for 93% reduction in mercury emissions. Even with this large reduction in the primary source of mercury, some lakes and rivers are not expected to meet the mercury standard in fish tissue. This presentation will cover the results and implications of a recently completed study of probable causes of increased efficiency of mercury transmission to fish in six northern Minnesota rivers. All but one of the rivers are impaired for mercury in fish. They are distinctly different in their mix of land cover and water chemistry. Three processes were measured: (1) mercury flow through the watershed, (2) conversion of mercury to methylmercury, and (3) accumulation of methylmercury in the riverine food web.

Dr. Monson is a research scientist at the Minnesota Pollution Control Agency, where he coordinates fish contaminant studies. He is also Adjunct Assistant Professor in Fish, Wildlife, and Conservation Biology. He received his bachelors and Ph.D. from U of M and masters from the University of Illinois.