Production and release of dimethyl sulfide from the Great Lakes

Dimethyl sulfide has been detected in all the water samples from Lakes Superior, Erie and Ontario. The average concentrations in the surface waters were 5.2 ng l^-1 for Lake Superior, 16 ng l^-1 (June) and 7.3 ng l^-1 (August) for Lake Erie and 27 ng l^-1 (June) and 13 ng l^-1 (August) for Lake Ontario. The profiles in the water column and the seasonal variations (with highest concentrations following after the crash of spring diatom bloom) suggest that DMS production in these lakes stems primarily from the microbial decomposition of dead algal cells. Only a small fraction (<5%) of the sulfur used in planktonic protein synthesis is converted to DMS, however. The emissions of DMS to the atmosphere were calculated to be 107, 49 and 69 tonnes year^-1 respectively in Lakes Superior, Erie and Ontario. The biogenic sulfur emissions from the lakes are thus insignificant compared to the contributions from anthropogenic sources in the Great Lakes basin.