SS4.02 The Role of Microbiology in Trace Metal and Organic Contaminant Cycling in Aquatic Systems
Date: Wednesday, June 12, 2002
Time: 10:30:00 AM
Location: Esquimalt
LosetoLL, University of Ottawa, Ottawa, Canada,
Siciliano, S, D, University of Gent, Gent, Belgium,
Lean, D, R, University of Ottawa, Ottawa, Canada,
In low latitude environments, wetlands have been identified as MeHg sources with the methylmercury formed via conversion of Hg(II) to MeHg by sulfate reducing bacteria (SRB). In this study we evaluated if wetlands were sources of MeHg to arctic watersheds and if SRB were the organisms responsible. Soil and surface water samples were collected at 15 wetlands on Cornwallis Is., NT and were analyzed for MeHg as well as sulfate reducing activity. In frozen soil MeHg was generally low (15-300pg/g) but MeHg values in water during and after snowmelt were relatively high (1500pg/L). In soils that were incubated at 4C or 8C for 30 and 60 days, MeHg levels increased to 1000-10,000pg/g. Sulfate reducing activity as assessed the radiotracer 35S showed very low activity of less than 1 nmole/day/g of soil. Fatty acid methyl ester analysis and DNA analysis of soil indicated that SRB were responsible for discriminating between samples containing high and low levels of MeHg but that there organisms were present in very low concentrations. This work confirms that wetlands produce high levels of MeHg during the brief arctic summer but the role of SRB in the arctic MeHg cycle is unclear.