Diatom-based transfer functions for inferring past climatic and environmental changes in Alaska, USA

Surface sediment diatom assemblages from 51 Alaskan lakes, distributed alon g a north-south transect, were enumerated in order to develop transfer func tions that could be used to make inferences of past climatic and environmen tal change. Environmental variables that were found to be the strongest pre dictors of the diatom assemblages, identified through Canonical Corresponde nce Analyses, were ionic and nutrient concentrations, as well as lake depth . A number of weighted-averaging (WA) regression-calibration techniques wer e employed to develop transfer functions for lake-water conductivity, total phosphorus concentration, and lake depth, but simple WA with classical des hrinking produced the most robust models for all variables. The strength of these models (r(boot)(2) ranged between 0.52 and 0.53) is comparable to th ose generated from other northern calibration studies. Application of our m odels to fossil diatom assemblages could provide information on the magnitu de of past environmental change, and may serve as a basis for assessing ant hropogenically induced impacts.