"Life under the ice" - winter ecology of temperate rivers

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Aquatic environments in Canada are exposed to extreme seasonal variation in temperature, productivity and food availability. Surprisingly however, our understanding of the ecological function of river ecosystems is overwhelmingly derived from studies conducted during the ice-free months and remarkably little of known regarding how these ecosystems function during winter. Hence, as periods of winter ice cover become shorter we lack the fundamental knowledge to determine what component of ecosystem function is being lost and how to mitigate these effects. Over the next 5 years, I will conduct a field-based research program to a) determine winter ecology of river communities, characterising the food web structure and ecosystem function of ice-covered rivers and b) assess how climate change may modify these interactions and influence ecosystem function. In Objective 1, MSc1, 2, 3 and I will conduct seasonal (fall, winter and spring) sampling in rivers in New Brunswick to assess seasonal variation in the community structure and function of river communities. MSc1 and I will use stable isotope analysis, chromatography, microscopy and DNA analysis to assess seasonal variation the community structure and nutritional quality of biofilm, the base of temperate river food webs. MSc2 and I will use quantitative ecology and stable isotope analysis to determine seasonal variation in the community structure and resource use of invertebrate communities. MSc3 and I will use diet and stable isotope analysis to assess the trophic ecology and energy pathways supporting fish communities in ice covered rivers. In Objective 2, PhD1 and I will employ the methods developed in Objective 1 in eight New Brunswick rivers spanning a latitudinal gradient equating to a 2°C range in mean annual temperature and including four groundwater fed rivers which remain ice free during winter months. We will conduct seasonal sampling of primary producers, aquatic invertebrates and fishes at each site and use a combination of stable isotope analysis, fatty acid analysis and quantitative ecology to identify how variation in length and intensity of winter influences the structure and function of temperate river food webs. This program will train 4 graduate and 9 undergraduate HQP and will provide a unique insight into seasonal variation in river ecosystem function. This work will advance the field of ecology by developing a novel characterization of the links between structure and function of aquatic communities which incorporates seasonal changes in the river environment. In addition, it will provide a better method to predict the effect of climate change on riverine communities and establish a model which can be applied to temperate rivers across Canada.