ASSESSMENT OF FRESH-WATER DIATOMS AS QUANTITATIVE INDICATORS OF PAST CLIMATIC-CHANGE IN THE YUKON AND NORTHWEST-TERRITORIES, CANADA

We identified, enumerated, and interpreted the diatom assemblages pres erved in the surface sediments of 59 lakes located between Whitehorse in the Yukon and Tuktoyaktuk in the Northwest Territories (Canada). Th e lakes are distributed along a latitudinal gradient that includes sev eral ecoclimatic zones. It also spans large gradients in limnological variables. Thus, the study lakes are ideal for environmental calibrati on of modern diatom assemblages. Canonical correspondence analysis, wi th forward selection and Monte Carlo permutation tests, showed that ma ximum lake depth and summer surface-water temperature were the two env ironmental variables that accounted for most of the variance in the di atom data. The concentrations of sodium and calcium were also importan t explanatory variables. Using weighted-averaging regression and calib ration techniques, we developed a predictive statistical model to infe r lake surface-water temperature, and we evaluated the feasibility of using diatoms as paleoclimate proxies. This model may be used to deriv e paleotemperature inferences from fossil diatom assemblages at approp riate sites in the western Canadian Arctic.