Paleoenvironmental investigation of an emerging stressor to Canadian salmon rivers

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A long-term perspective is useful to distinguish natural ecosystem variability from human impacts, and to recognize the rates and magnitude of environmental change. Paleolimnology is the science that uses the physical, chemical, and biological information preserved in sediment records to track environmental changes over long periods of time, often decades to millennia. My research program combines a paleolimnological approach and modern ecological sampling to better understand how freshwater ecosystems respond to natural processes and human-caused stressors. This interdisciplinary approach can be a powerful tool to determine cause-and-effect, establish baseline ecosystem conditions, and set realistic recovery goals following the impacts from human activities. My proposed research program aims to understand the causes and effects of nuisance growths (blooms) of the bottom-dwelling alga, Didymosphenia geminata (Didymo), in remote, pristine salmon rivers in western (Vancouver Island, BC) and eastern (Gaspe region of QC and northern NB) regions of Canada. By studying the information preserved in sediment records within regions currently experiencing nuisance Didymo blooms we will be able to assess the long-term environmental drivers that cause blooms to form and proliferate across these ecosystems. This temporal perspective will allow us to determine whether climatic change, nutrients from global atmospheric pollution, or historic land-use practices are impacting freshwaters where Didymo blooms occur. These widespread stressors are believed to create conditions favorable to bloom formation and persistence, although detailed evaluations have not occurred to date. Our approach can recognize whether recent Didymo blooms are unprecedented over the last ~2000 years or whether blooms have occurred in the distant past. We will also conduct a modern ecological study of river habitats in two eastern Canadian rivers by sampling invertebrates, algae, and juvenile Atlantic salmon. This approach will help us to understand how Didymo blooms affect river habitat and ultimately impact the diet of juvenile salmon. At sites with and without Didymo blooms, we will investigate differences in food web structure and the quantity and quality of prey that juvenile salmon consume. A greater understanding of both the causes and effects of Didymo blooms will provide government and ecosystem managers with scientific knowledge to aid in the management of these iconic Canadian salmon rivers experiencing recent benthic algal blooms.