ASSESSING THE INFLUENCE OF A WARMING CLIMATE ON THE BIOTA OF ARCTIC FRESHWATER SYSTEMS

Abstract

Understanding the effects of climate change is particularly important for northern regions, where temperatures have increased by considerably more than that of the global average since the start of the 20th century. As a result, freshwater lakes and ponds found throughout the subarctic and Arctic are now under a great degree of ecological stress. The way these systems have responded to this stress has not been uniform and it is unclear how aquatic biodiversity has been affected by climate related stress as well as anthropogenic development. As such, this thesis attempts to broaden our understanding of how aquatic biodiversity of small freshwater ponds and lakes in the eastern Canadian subarctic and Arctic have changed as warming has intensified during the Anthropocene. A chironomid-based paleolimnological analysis of lakes in northern Manitoba and Baffin Island, Nunavut, showed that the divergent prevailing ecological conditions in different northern regions have had significant effects on freshwater biodiversity. In the Arctic warming has led to an increase in diversity as the warm conditions increased the amount of habitat available to warm water taxa. In particular, lakes within the urban boundary of Iqaluit, Nunavut, primarily responded to regional warming, and had very little change associated with anthropogenic development during the last century. In the subarctic warming has increased evaporative pressure on the shallow lakes and ponds characteristic of the region. As such, warming has had less of an influence than landscape-mediated changes to aquatic environments. Understanding how these sensitive ecosystems have been affected by climate change is critical to understanding future responses as warming becomes more intense in the future