My research program focuses on understanding the impacts of human activities on aquatic ecosystems. More specifically, my students and I study the effects of point (municipal, industrial) and non-point (agriculture, forest harvesting) discharges on the health of aquatic organisms, and the fate of persistent pollutants in freshwater and marine ecosystems. Much of our research is multidisciplinary in nature and an interface between biogeochemistry, chemistry, ecology and toxicology. For example, we use measurements of stable nitrogen, sulfur, hydrogen and carbon isotope ratios in organisms to characterize trophic relationships in diverse aquatic systems and to understand pollutant accumulation from primary producers through to top predators. I have led or been involved in three major whole ecosystem experiments to understand how 1) the estrogen used in the birth control pill affects fish and their prey, 2) wastes from rainbow trout aquaculture affect native organisms, and 3) a commonly-used herbicide and fertilizers affect the health of wetland communities.
Contaminants in Aquatic Food Webs
Some contaminants can concentrate up through food webs to levels in fish that can affect the health of the fish themselves or that of fish-eating wildlife and humans. Even in remote systems with no human activities, mercury and other contaminants can be high in fish leading to concerns over risks to human and wildlife health. We have several ongoing projects to understand how contaminants are accumulated through aquatic food webs into top predators and their effects on fish.
• Mercury in lakes in Atlantic Canada – We are working in Kejimkujik National Park, Nova Scotia, an area known as a mercury hotspot, and developing novel approaches for understanding how mercury moves through the food webs of these acidic lakes and whether it is adversely affecting the health of the fish.
• Mercury in the Canadian Arctic – We have studied mercury in an important subsistence fish – the Arctic char – and its prey to understand why fish from some lakes are more contaminated than others.
• Mercury in coastal regions of Patagonia, Mexico, and Antarctica – We are assessing the levels of mercury and other metals in marine fish and invertebrates, some of which are consumed by local communities.
• Other global studies on mercury – My group and I also have ongoing research across a latitudinal gradient in Norway and Sweden to understand the effects of climate and organic matter on mercury cycling in lakes, and collaborations to assess global patterns of mercury in freshwater and marine food webs.
• Nutrients and metals from aquaculture – At several salmon aquaculture sites in the Bay of Fundy, we are examining the exposure of nearby organisms to both nutrients and metals from wastes.
Contaminants of emerging concern – including estrogens and their mimics – in municipal wastewater treatment plant (MWTP) effluents have the potential to disrupt the normal function of endocrine systems and impair reproduction and development in fish and other organisms. Approaches are needed to understand whether these chemicals are causing biological effects downstream of MWTPs, and to prioritize sites for further work.
My lab is involved in a collaborative program through the Canadian Water Network to identify a suite of measures that clearly indicate that biological effects are occurring as a result of the presence of effluent discharges, and a practical basis for distinguishing the relative level of concern among sites. In addition, we conducted a whole ecosystem experiment at IISD-Experimental Lakes Area in northwestern Ontario over 12 years to assess the effects of the estrogen used in the birth control pill – EE2 – on fish populations and the food web.
Funding: These projects have been supported by NSERC Discovery & Strategic Network Grants, New Brunswick Environmental Trust Fund, New Brunswick Wildlife Trust Fund, INAC Northern Contaminants Program, Polar Continental Shelf Project, Fisheries & Oceans Canada, Schering Pharmaceutical, Environment Canada, Parks Canada, Canadian Water Network, Norwegian Research Council, and Fundación MERI Chile.
Forest management and stream health
Nearly two-thirds of Canada’s land base is forested, and this forms the basis of one of Canada’s most important resource industries. However, forests are also key suppliers of aquatic ecosystem services (AES), such as serving as critical source areas for much of North America’s sustainable, clean water supplies and supporting aquatic biodiversity. This research is providing information on how forest management activities affect aquatic ecosystems to inform sustainable forest management practices.
Through several projects in New Brunswick and Ontario, we are exploring 1) the change in physical, chemical and biological indicators (water quality though food web structure) of stream health across a gradient of forest disturbance, and 2) the cumulative effects of forest management practices on downstream ecosystems and their services (fish and invertebrate communities, water quality, mercury accumulation, carbon inputs and cycling), using intensively- through minimally-managed watersheds on forested landscapes.
Funding: This research is supported by an NSERC Strategic Network grant, an NSERC CRD and considerable in-kind support from the Canadian Forest Service (NRCan) and JD Irving, Ltd.
Dams and dam removal
In Canada, there are > 10,000 known dams, > 580 of which are large hydroelectric facilities. Much of this infrastructure is aging and will require removal or replacement in the decades to come, motivating an emerging field in Canada and abroad – the science of dam removal. One such facility – the Mactaquac Dam – is on the Saint John River in New Brunswick, and it will reach the end of its service life in 2030.
The Mactaquac Aquatic Ecosystem Study (MAES) is a whole ecosystem study to understand the structure and function of the Saint John River and the potential implications of removal of the Mactaquac Dam upstream of Fredericton. As part of this multi-disciplinary, multi-institutional project we are assessing the structure of the riverine food web and the contemporary and historical concentrations of metals, hydrocarbons and chlorinated organics (e.g. PCBs) in the sediments of the headpond. These results will be used to support the decisions around dam removal or refurbishment.
Funding: This project is led by the Canadian Rivers Institute @ UNB and funded by NB Power and by an NSERC CRD Grant.
Contaminants in Aquatic Food Webs, Forest management and stream health, Dams and dam removal