HR: 08:30h
AN: B41F-03    [Abstracts]
TI: Climatic Control of Trophic Status of Shallow Lakes on the Boreal Plain of Alberta, Canada
AU: * Sass, G
EM: gzsigovi@uwo.ca
AF: The University of Western Ontario, Department of Geography Social Science Centre, London, ONT N6A 5C2 Canada
AU: Creed, I F
EM: icreed@uwo.ca
AF: The University of Western Ontario, Department of Biology, Biological & Geological Sciences Building, London, ONT N6A 5B7 Canada
AB: Trophic status is a broad measure of the productivity of aquatic ecosystems but it can also serve as an important indicator of carbon and nutrient cycling within lakes. In shallow lakes of the boreal region of western Canada, the trophic status is usually clear, dominated by submersed aquatic vegetation, yet very dynamic, with individual lakes exhibiting switching from clear to turbid conditions and vice versa on an almost annual basis. Recent work has focused on gaining greater understanding on the spatial and temporal controls on the trophic status of lakes on the Boreal Plain. Here we tested the degree to which climate controls the trophic status of shallow lakes in a region of the Boreal Plain that is still largely undisturbed by human activity. Using a 20 year LANDSAT satellite dataset and corresponding field-based chlorophyll-a measurements for some of the satellite images, we derived trophic status estimates for approximately 100 lakes which were then averaged to produce a landscape average for each summer biomass peak between 1984 and 2003. We used regression and correlation analyses to assess the association between the satellite derived estimates of trophic status and climatic (e.g. total summer precipitation and potential evapotranspiration) and hydrologic variables (e.g. percent of the landscape that is inundated). Contrary to our expectations, we found that wetter conditions lead to more clear lakes, a possible consequence of hydrologically mediated dilution of critical nutrients (i.e., phosphorus) and drier conditions result in more turbid lakes due to concentration of nutrients in shallow waters (< 1.5 m). Weak but significant correlation between local climate and the Pacific Decadal Oscillation suggested that the next 20 years might be colder and wetter and therefore result in clearer lakes assuming no major changes in human activities that lead to water quality changes. Understanding the controls on the natural variation in trophic status is important if we are to better anticipate the impacts of predicted climate change on the productivity of these boreal aquatic ecosystems.
DE: 0429 Climate dynamics (1620)
DE: 0458 Limnology (1845, 4239, 4942)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0480 Remote sensing
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: Fall Meeting 2005