Differences among modern-day and historical cladoceran communities from the “Ring of Fire” lake region of northern Ontario: Identifying responses to climate warming

Abstract

The Ring of Fire in the Far North of Ontario (50 - 57° N, 79 - 94° W) is a region of growing economic and environmental interest due to recent mineral discoveries and the potential for resource development. Due to the remote location of the region, little baseline ecological information is available to distinguish any environmen- tal impacts of mine development from ongoing regional warming. Here, we compare modern and pre-industrial sedimentary cladoceran assemblages from 60 lakes centered on McFaulds Lake in the Ring of Fire to identify directional changes through time and compare the assemblages with prior paleolimnological cladoceran studies of Ontario lakes closer to the Hudson Bay coast, and further south in the Muskoka-Haliburton region. The cladoceran assemblages from the Ring of Fire contain diverse littoral assemblages relative to the other two regions; however, despite the shallow depth of these lakes, there have been significant increases in the relative abundances of pelagic taxa (e.g. Bosmina spp. and Daphnia spp.) since pre-industrial times; taxonomic shifts consistent with warming- induced changes in lake properties including a longer ice-free period and increased algal plankton production. This evidence of widespread changes within the cladoceran assemblages in the Ring of Fire prior to the onset of resource extraction provides lake managers and stewards with information to better monitor and evaluate future development projects.