Using paleolimnology to assess the effects of multiple stressors on Boreal Shield lakes

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The structure, function and biodiversity of freshwater ecosystems are being altered by multiple environmental stressors that often interact in complex ways. A diverse set of approaches are needed to understand the impacts of these stressors of inland lakes, and on the ecological services they provide (e.g., recreation, fishing, drinking water). For example, an understanding of baseline conditions prior to the onset of recent disturbances can be used to distinguish novel trends from natural variability or long-term cycles. Moreover, long-term data can be used to place recent changes in a historical context, providing realistic lake management targets for resource managers. To provide a long-term context, my research will use a combination of long-term monitoring data (seasons to decades), spatial surveys, and information preserved in lake sediments (decades to centuries), to assess the unique and interactive effects of multiple stressors on water quality and biological communities in Boreal Shield lakes. My students and I will explore the drivers and the ecological and management implications of two important issues presently affecting inland lakes within the southern Boreal Shield: 1) increasing dissolved organic carbon concentrations (i.e., lake brownification); and 2) increasing chloride concentrations associated with road salt applications. My research on the long-term drivers of lake brownification will be used to update predictive models for assessing impacts of land-use change and shoreline development on deep water oxygen concentrations in lake trout lakes. These models are used daily by resource managers in Ontario, as they make decisions regarding >1000 new or redeveloped cottage lots per year. New research that quantifies ecological thresholds from road salt application is also urgently needed, given recent results showing that current water quality guidelines for chloride may not adequately protect aquatic life in nutrient-poor lakes. In closing, my Discovery Grant will train eight HQP (four graduate and four undergraduate students), and the research generated will contribute the novel and defensible science needed to develop effective lake management guidelines and policies.