Does a one point sample adequately characterize the lake environment for paleoenvironmental calibration studies?

Abstract

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.