Understanding the effects of terrestrially-derived dissolved organic matter on food web productivity and organismal life histories in lakes

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Lake ecosystems and the services that they provide to people are profoundly influenced by inputs of terrestrially-derived dissolved organic matter (tDOM). Inputs of tDOM to lakes vary across the landscape; they have also increased over the past several decades in many regions, and are likely to continue to change. Given these two observations - that tDOM inputs fundamentally shape lake ecosystems, and that these inputs vary in space and time - what are the implications for the productivity of these systems and the culturally and economically valuable fisheries that they support? We will address this question from two different perspectives. First, we will test a new theoretical framework describing the effects of tDOM on food web productivity. Our tests will include replicated experiments, comparative studies, and a whole-lake tDOM manipulation, in which we will assess how productivity of algae, invertebrates, and fishes respond to differences in tDOM inputs. Second, we will ask how differences in tDOM inputs affect the life histories (e.g. growth rates, maturation ages, and fecundities) of two different organisms, bluegill sunfish and non-biting midges. These are widespread and well-understood species, and so are good model systems for understanding how tDOM influences optimal life history traits. This work will have major benefits for the research field and for Canada. It will provide rigorous tests of cutting-edge theory in aquatic ecosystem ecology, increasing our understanding of how these systems work and how they may respond to ongoing environmental changes. It will inform current and future management of inland recreational fisheries, which are a valuable cultural and economic resource for Canadians.