1. Integrate modeling with NOAA hydrodynamic model for Lake Ontario to estimate flux of materials to benthos 2. Assess concentration and composition of microplastics in water and sediments of tributaries and Lake Ontario 3. Evaluate microplastic transformation and toxicity to key model organisms and subsequent impacts on ecosystem processes 4. Assess impact of microplastics on microbial community structure and function 5. Quantify invertebrate-mediated burial and resuspension of plastics 6. Conduct outreach to communicate results and bolster community engagement

1. Develop a 3-dimensional transport model of Lake Ontario that will be used to predict a spatially explicit and compound-specific flux of plastic particles to the sediment. 2. Analyze in-hand and new sediment samples from South Shore tributaries and the nearshore, to assess the concentration, size distribution, and polymer composition of plastics in the benthos. 3. Conduct aging experiments across plastic types to evaluate transformations in plastic size, composition, biofilm formation and microbial community structure and function. 4. Using outcomes from modeled and measured benthic plastic concentration and composition, assess impact of plastics on (1) key benthic invertebrates and microbes in traditional ecotoxicology assays, and (2) benthic biogeochemistry and ecosystem functions, (3) microbial community structure and function, and (3) resulting ecosystem services. 5. Measure reciprocal impacts of benthic organisms on microplastic fate in the benthos using advanced particle imaging techniques. 6. Working in partnership with regional educational and outreach organizations, develop outreach materials and engage the community to foster knowledge of the problem that will ultimately lead to greater community engagement with the problem of plastic pollution.

Accumulation of plastic debris in terrestrial and aquatic environments is a pressing environmental issue with largely unknown implications for ecosystems and human health. The vast majority of research on this issue to date has been conducted in the oceans, or in the pelagic zone of lakes, in spite of the relatively high concentrations of plastics found in freshwater sediments. However, sediment data are sparse because field-based quantification surveys are time-consuming and expensive. Further, work to date has addressed plastic pollution as a single problem, when in reality, the plastic particles that reach aquatic ecosystems, and are ultimately delivered to the benthos, is derived from a very large array of compounds that vary substantially in size, density, composition, and degree of environmental transformation. Once deposited in the sediments, reciprocal interactions between benthic organisms and plastic contaminants occur, further affecting both the fate of the plastic and the resulting impact to ecosystem functions and services. These factors lead to substantial variation in potential ecotoxicity, cascading effects on ecosystem processes and trophic structure, and ultimately human health. As a result, there is insufficient spatial and temporal resolution of plastic debris quantity and quality in the Great Lakes to effectively inform policy, mitigation, prevention initiatives, resource management strategies, and the design of targeted research surveys, experiments, and technological innovations. Our proposal addresses this knowledge gap by combining sediment sample analysis with three-dimensional transport modeling to produce the first estimates of polymer-specific plastic flux to the sediment. These estimates will then inform toxicity experiments at environmentally relevant concentrations to assess effects on and of key organisms to understand the impact of plastics on delivery of benthic ecosystem services.