Alkenones are common in prairie lakes of interior Canada

Long chain alkenone (LCA) lipids produced by haptophyte algae are ubiquitous in marine environments and are increasingly reported from enhanced conductivity, solute rich lakes worldwide. Following our survey of lakes in the United States (Toney et al., 10.1016/j.gca.2009.11.021), we examined surface sediments from 19 lakes in central Canada for alkenones and compared our data with lake characteristics. We found that 68% of surveyed lakes contained sedimentary LCAs, all have C-37:4me dominated profiles. Lakes containing LCAs had salinities > 1.5 g/l and SO4/CO3 ratios > 3.5. LCA concentrations were highly elevated (Sigma C-37 > 500 mu g/g sediment) in sediments of meromictic lakes with permanently anoxic deep waters. Overall, the distribution of LCAs was consistent with a previous survey of lakes in the interior of the United States demonstrating that tetra-unsaturated lipids were most common in sulfate rich, saline lakes. Alkenone unsaturation indices (U-37(K)) from the upper 10 cm of the sediment column are weakly correlated with point sampled average spring water temperature (r(2) = 0.30, p = 0.067) and the range of inferred temperatures is in agreement with the average, long term potential evapotranspiration weighted temperature. (C) 2011 Elsevier Ltd. All rights reserved.