Branfireun, M. L.. Dept. of Geography, McGill University,
Moore, T. L.. Dept. of Geography, McGill University,

Peatlands have been shown to be large sources of methylmercury (MeHg) to downstream aquatic ecosystems in some environments. One potential mechanism by which this MeHg may be made available is through the decomposition of peatland vegetation. The decomposition rates and MeHg burden of Sphagnum angustifolium, Sphagnum fuscum, Chamaedaphne calyculata were measured in hummocks, hollows and lawns of a poor fen in the Experimental Lakes Area, northwestern Ontario. Decomposition rate usually decreased with depth below the water table, was highest in hummocks and lowest in hollows and was generally highest for C. calyculata and lowest for S. fuscum. All litter types increased in methylmercury burden over time, particularly in lawns and near the water table. Both decomposition and MeHg burden were found to be unexpectedly high in certain locations well below the water table. While litter quality seems to be the dominant control on rate of decomposition in the near-surface environment, rate of change in litter methylmercury concentration appears to be controlled mainly by microtopography, proximity to the water table, and perhaps localized subsurface phenomena, not by initial tissue burden. This indicates that decomposition in fens is linked to methylmercury cycling mainly via the provision of organic substrates for methylation.
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
Code: CS63TH1204S