Twin Cities WRS Seminar

Controls on Mercury Cycling and Bioaccumulation in Fish in Northern Minnesota


Dr. Randy Kolka
USDA Forest Service

December 1, 2017


Mercury is the number one contaminant in surface waters of the US because of health concerns for both humans and other animals when they consume fish. The form of mercury that
bioaccumulates in the food chain is an organically complexed form known as methylmercury (MeHg). Over the past 20 years we have conducted research to understand the mercury cycle in Northern Minnesota. Notable studies have characterized how both total mercury and methyl mercury cycle in peatland watersheds, the controls on the production of methylmercury and bioaccumulation in fish, the effect of increasing sulfate deposition on mercury fluxes in both water and biota, and the influence of forest fire on mercury cycles. I will discuss these studies and summarize the current state of knowledge on mercury cycling.

Dr. Randy Kolka holds a B.S. degree in Soil Science from the University of Wisconsin-Stevens Point, and MS and PhD degrees in Soil Science from the University of Minnesota. Following the completion of his PhD in 1996, he was a post-doctoral Research Soil Scientist with the USDA Forest Service’s Southern Research Station on the Savannah River Site in South Carolina. In 1998 he became an Assistant Professor of Forest Hydrology and Watershed Management in the Department of Forestry at the University of Kentucky. In 2002, he became Team Leader and Research Soil Scientist with the USDA Forest Service’s Northern Research Station in Grand Rapids, MN. In this position, he currently leads a team of scientists, graduate students and post-docs conducting research on the cycling of water, carbon, nutrients, mercury and other pollutants at the plot to watershed scale in urban, agricultural, forested, wetland and aquatic ecosystems across the globe. He is an adjunct faculty member at 6 universities and has published over 180 scientific articles in his career.