Predicting dissolved oxygen concentrations in Lake Trout lakes: Developing new tools for a multiple-stressor world

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Canada's Lake Trout lakes are a rare and valuable natural resource in both economic (in Ontario alone, anglers spend an estimated 1. 7 billion dollars on goods and services related to recreational fishing, with lake trout being the preferred species among many anglers) and ecological terms. However, lake trout populations are becoming increasingly threatened by multiple environmental stressors (e.g., over-exploitation, competition with introduced species, nutrient loading), with the added "threat-multiplier" of accelerated climate warming. There is growing concern that habitat quality in the deep waters of many Lake Trout lakes is declining due to oxygen depletion. Moreover, new evidence suggests that declines in deepwater oxygen concentrations may be occurring in lakes where nutrient inputs have not increased, or even where phosphorus inputs or lake nutrient concentrations have decreased over time, creating exceptions to the "increased nutrients, decreased deepwater oxygen paradigm". This is of particular concern because current approaches to resource management are prefaced on this major assumption, and thus are problematic in a multiple stressor world, and especially when climate change is affecting lake ice cover and thermal stratification, and consequently deepwater oxygen levels. It is clear that managers need a new toolset, one that includes predictive models for forecasting shifts in lake trout habitat and improves understanding of historical changes in lake trout habitat. This proposal brings together university researchers and partners with diverse expertise (e.g., modellers, engineers, biologists, paleolimnologists) to develop and apply three distinct, yet complementary, techniques to accurately predict past, present, and future deepwater dissolved oxygen concentrations in Lake Trout lakes. This project will also provide an outstanding training program for our students and post doc, blending diverse but complementary approaches, with direct interactions with our trans-disciplinary supporting organizations and other users. In a multiple-stressor world, these novel tools will provide managers with a scientifically-defensible approach for managing lake trout habitat, provide guidance on mitigation strategies, and ensuring sustainable management.