Cycling and trophic transfer of metals in a changing environment

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Climate change, new mining projects, increased atmospheric deposition from emerging Asian economies, and introduction of new substances in urban areas will modify the emission, transport, transformation and fate of metals in Canada, with unknown consequences on ecosystem health. For instance, there are currently 200 mining projects under consideration for rare earth elements (REEs) in Canada, a group of metals little known from an ecotoxicological standpoint, whereas mercury (Hg) emissions are expected to rise considerably in the next decades. Our long-term research plan focuses on the biogeochemistry and food web transfer of metals up to human exposure in changing environment. In the past 6 years, I (co)supervised 58 highly qualified personnel (HQP); my team and I published 37 peer-reviewed papers and presented 121 times at conferences. In the next five years, we will build on our recent advances by conducting targeted studies on emerging issues related to metal biogeochemistry. Theme 1. First, our recent work has suggested that aquatic biofilms may form key sites of transformations of Hg in the North (unstratified polar thaw ponds) and in the south (St. Lawrence River). We will establish what controls metal complexation in these biofilms and how emergent contaminants such as microplastics, can modify biofilm/metal interactions. Theme 2. Most trophic transfer studies of contaminants use stable isotopes of N and C to understand food web relationships and transfer. We will assess a complementary conceptual approach based on subcellular partitioning of metals and use it on single metals, including those of emergent concerns (i.e. REE), and antagonistic combinations of metals. 16 HQP will be trained through this interdisciplinary program, at the intersection of ecology, toxicology, genomics and analytical chemistry, preparing them for the job market of tomorrow. This program will allow to better predict the fate and effect of metals in a changing environment. It will lead to significant fundamental advances regarding the role of aquatic biofilms in metal cycling and the mechanism involved in metal trophic transfer. The data generated on REE transformation and trophic transfer will be the first of this kind in Canada and will inform decision-makers at the dawn of an era of REE mining in this country. The study on the effect of MP on metal cycling will likely be the first in Canada and will help assess risk associated with this emerging threat.