Lakes in the far north of Ontario: regional comparisons and contrasts

Abstract

With the large scale of anticipated mining development in the Ring of Fire (ROF) area and the potential for other future industrial developments and rapid climate change in the north, there is a great need for basic limnological data for lakes in the Far North of Ontario. To address this need, water chemistry and crustacean zooplankton surveys of northern Ontario lakes were conducted to examine regional differences between lakes of the Precambrian Shield and Hudson Bay Lowlands, focusing on the ROF area, which straddles the boundary between these physiographic regions. Lakes of the ROF area displayed highly variable water chemistry, a product of the extensive peatland landscape with its mix of bog and fen watersheds. This peat cover appears to decouple, to varying degrees, the lakes from the influences of bedrock and surficial geology and is a source of complex organic matter and acids. Shield lakes in the western portion of our study area had base cation concentrations (Ca, Mg) markedly higher than those of previously studied Shield lakes south of 50°N, likely due to the abundance of lacustrine and glacial end-moraine deposits throughout western Ontario north of 50°N. The zooplankton species collected during this survey were generally similar to those reported for lakes further south on the Precambrian Shield. Zooplankton assemblages were strongly influenced by lake morphometry, with higher species richness in the deeper Shield lakes than in the shallower Lowlands lakes which would appear to offer less niche space for coexistence of species.