My main research area is the biogeochemistry of mercury in the aquatic environment. I am interested mainly in processes leading to mobilisation and export of mercury from soils to surface waters, and in processes causing mercury methylation. Methyl mercury is highly bioavailable and reaches high and potentially harmful concentrations in top predator fish, even in pristine boreal forest lakes that receive mercury pollution only through atmospheric deposition.
The biogeochemistry of mercury is closely related to the biogeochemistry and turnover of organic matter, because mercury has strong affinity for reduced sulfur groups (thiol groups), and because organic matter drives microbial activity that is responsible for various conversions of mercury, including its methylation. As for the carbon cycle, the mercury cycle is strongly affected by hydrology, temperature and by various cations in the water.
Another element cycle that interacts strongly with the mercury cycle is the sulfur cycle. Sulfate-reducing bacteria conver organically bound mercury to mercuric sulfide complexes, some of which are fat soluble and taken up by bacteria. The formation of these complexes appears to be the first step in the microbial methylation of mercury.
Lately, I have been studying sites that are affected by a combination of high organic matter loads and mercury pollution. Typically the microbial activity is very intense, leading to anoxic conditions and sulfide formation during summer. However, a high surplus of organic carbon means that other nutrients like phosphorus can have a strong impact on organic matter turnover and on mercury speciation.
Regnell, O.; C. J. Watras; B. Troedsson; A. Helgée; T. Hammar. 2009. Mercury in a boreal fores stream role of historical mercury pollution, TOC, temperature and water discharge. Environ. Sci. Technol. 43: 3514-3521.
C. J: Watras; K.A. Morrsion; O. Regnell; T. K. Kratz. 2006. The methylmercury cycle in Little Rock Lake during experimental acidification and recovery. Limnol. Oceanogr. 51: 257-270.
Kent, A. D.; C. J. Watras, C. Eckley; O. Regnell; K. D: McMahon; H. Hintelmann: 2005. Mecury methylation varies with pelagic MCC in lakes within the Great Lakes basin. 2005 Annual Meeting of the International Association for Great Lakes Research.
Watras, C. J.; K. A. Morrison; A. Kent; N. Price, O. Regnell; C. Eckley; H. Hintelman; T. Hubacher. 2005. Sources of methylmercury to a wetland-dominated lake in northern Wisconsin. Environ. Sci. Technol. 39: 4747-4758.
Regnell, O.; T. Hammar. 2004. Coupling of methyl and total mercury in a minerotrophioc peat bog in southeastern Sweden. Can. j. Fish. Aquat. Sci. 61: 2014-2023.
Eckley, C.; C. J. Watras; H. Hintelmann; K. Morrison; A. Kent; O. Regnell. 2004 Mercury methylation in the hypolimnetic waters of lakes with and without connections to wetlands in northern Wisconsin. Can. j. Fish. Aquat. Sci. 58: 506-517
Regnell, O.; T. Hammar; A. Helgée; B. Troedsson. 2001. Effects of anoxia and sulfide on concentrations of total and methyl mercury in sediment and water in two Hg-polluted lakes. Can. j. Fish. Aquat. Sci. 58: 506-517.
Regnell, O.; G. Ewald; E. Lord. 1997. Factors controlling temporal variation in methyl mercury levels in sediment and water in a seasonally stratified lake. Limnol. Oceanogr. 42: 1784-1795.