Depositional history of micropastics in the Laurentian Great Lakes basin

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The Laurentian Great Lakes of North America contain almost 20% of the world's freshwater supply, but the lakes are constantly threatened by historic and emerging pollutants and contaminants. The most globally widespread of these contaminants is plastic, which is mass-produced for its strength, lightweight nature, low cost of production and transport, and resistance to degradation. Although plastics improve quality of life, their unique chemical properties result in their preservation and global accumulation. Microplastics, particles <5 mm in longest diameter, are particularly problematic because they have the potential to become ingested by organisms of all sizes. Although the majority of plastics produced are less dense than water, microplastics can sink if they contain mineral fillers, are encrusted by microorganisms, or are expelled in fecal matter. Organisms that dwell in and/or feed on benthic sediment have been shown to ingest microplastic fibres, beads and fragments. Sediment can therefore be used as a critical indicator of microplastics pollution in lakes and rivers. The proposed research program will provide the first comprehensive investigation of microplastics pollution in benthic sediment of the Great Lakes and their tributaries on which future long-term monitoring will build. The short-term objectives include: 1) Investigating the depositional flux of microplastics to lake bottom sediment using dated sediment cores, 2) Identifying the current depositional "sinks" or areas of concern where benthic microplastics accumulate in the Great Lakes and their tributaries, 3) Determining the tributaries and related factors controlling microplastic input into the lakes, and 4) Identifying the compositions of the predominant microplastics in benthic sediment in order to determine source products and locations.