Effects of forest harvesting on phytoplankton communities in boreal lakes: Establishing a reference condition

Twenty-one headwater lakes located in Northeastern Ontario, Canada were examined in 2002 and 2003 to assess water quality and phytoplankton community structure to establish a reference condition prior to forest harvesting. Water samples were analyzed for water quality parameters, chlorophyll a, phytoplankton abundance and biovolume. Canonical Correspondence Analysis (CCA) revealed a significant gradient of trophic condition ranging from dystrophic (high total organic carbon (TOC)) to oligotrophic (low TOC) lakes. Lakes with dystrophic characteristics contained taxa from the family Chrysophyceae. Two-way Analysis of Variance indicated that there was no significant (p > 0.05) difference between east and west shorelines within lakes with respect to abundance, biovolume, Simpson's diversity index and Chlorophyll a values. However, significant differences (p < 0.05) occurred between different lakes and across seasons. The results of this study will be used as a basis for comparing future studies that will assess the response of phytoplankton populations to harvesting in adjacent watersheds.