Decoupling natural and anthropogenic change at Alta Lake, Whistler, British Columbia: Implications for management


Small, recreationally important lakes are economically critical to communities across Canada. Currently the development of management practices to prevent the deterioration of water quality in these lakes is based on 1-2 year limnological assessments that are only able to provide short-term characterizations of water quality variability. Using carbon-dated sediment cores from Alta Lake, Whistler, British Columbia, this study reconstructed long-term changes in water quality using C/N stable isotopes, metals, and historical records. Evidence was found for large-scale landscape destabilization ca. AD 1650 and the rerouting of Twenty-one mile creek from Alta Lake to the Green Lake watershed by alluvial fan dynamics ca. AD 1770. Changes in productivity indicators (δ13C and δ15N) coincident with anthropogenic metal deposition (AD 1900 – present) were not similar to changes in productivity indicators associated with landscape destabilization and watershed dynamics, indicating human-induced nutrient loading and increased productivity. Limnological assessments of Alta Lake concluded that Alta Lake is an oligotrophic, clear-water lake with excellent water quality. This study confirmed these data but suggested that nutrient loading and increased productivity on Alta Lake is a result of human activity. These changes are subtle but indicate that a comprehensive assessment of nutrient input is necessary to prevent the further deterioration of water quality. The application of the paleolimnological method confirms that a long-term perspective on water quality variability facilitates effective management practices for Alta Lake and other small, recreationally important lakes across Canada.

Canadian Quaternary Association Biennial Meeting
Dewey Dunnington
Geoscientist, Programmer, Educator