Does a one point sample adequately characterize the lake environment for paleoenvironmental calibration studies?
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A major goal of paleolimnological studies is the quantification of past environmental conditions. This is accomplished by computing transfer functions relating organism assemblages to environmental factors. The environmental data are typically comprised of a point sample of water chemistry and other environmental parameters that are collected at the same time as a surface sediment sample. We explore whether the year of sampling of the environmental variables affects the parameterization of organism-environment relations, in particular chironomids, ostracodes and diatoms. Canonical correspondence analyses revealed that the year of sampling is of secondary importance when relating the organism assemblages to environmental variables, but only with the major explanatory variables. A chironomid-inferred bottom water temperature partial least squares transfer function revealed similar performance statistics between the years. Taxon optima and tolerances were computed for both years using weighted averaging, and the results are comparable. A paired t-test computed on the proxy-inferred bottom water temperature values indicated that the results between the 2 years are not statistically different. The results of this study provide guarded optimism that the methodology of estimating transfer functions as currently applied is not entirely determined by the particular year when the data were collected, although more case studies are needed.
KeywordsPaleolimnology Calibration sets Transfer functions Canonical correspondence analysis Limnology Southwest Yukon
We thank P. Johnson, B. O’Neil, M. Vetter, S. Wilson and the students of GEG4001 (2000) for help in the field. This work was funded by a Natural Sciences and Engineering Research Council of Canada (NSERC) grant to Gajewski. Further funding was provided by a Northern Research Endowment Grant from the Northern Research Institute at Yukon College and Northern Scientific Training Program awards to Bunbury. We thank the staff at the Kluane Lake Research Station for their support, and the Champagne-Aishihik First Nations, the Kluane First Nations, and the White River First Nations for allowing access to their land to conduct this research. The quality of this manuscript was improved by comments from Roland Hall and an anonymous reviewer.
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