Submerged aquatic vegetation in Cook's Bay, Lake Simcoe: Assessment of changes in response to increased water transparency

A high frequency echo sounding method was employed to assess the extent of SAV cover and depth of colonization in Cook's Bay, Lake Simcoe during the late summer of 2006 and 2007. Results from this study are compared to historical echo sounding surveys in Cook's Bay conducted in 1984 and 1987, prior to reductions in point source phosphorus loads to the lake and before dreissenid mussel invasion. This study revealed that the total area of inner Cook's Bay covered by SAV has increased 65% since 1987, and SAV coverage extends to depths approaching 10 m. The areal expansion of SAV and increased depth of colonization are consistent with observations of increasing water transparency documented by the Ontario Ministry of Environment since the 1980s. Tissue nutrient content (N and P) of SAV growing in Cook's Bay during 2006 was found to be significantly lower than nutrient content measured in 1984 suggesting that light availability has increased relative to nutrient availability to SAV. The results of this study support are consistent with other studies demonstrating an areal expansion and increased depth of SAV colonization in response to increased water transparency.