There were more microplastics in nearshore sediment than in deep-water sediment. In fact, this was the strongest result of this study, suggesting that shoreline sources are creating microplastic hotspots in the sediment.
Deep-water sediment is often sampled in lake studies because these areas act as long-term sinks and experience relatively little physical disturbance. These samples provide a useful background estimate of accumulation. Near-source sampling is also common and important in areas with potential local sources, such as docks, beaches, marinas, or developed shorelines.
The student collected nearshore sediment samples (less than 80 m from shore) and found microplastic concentrations ranging from 0 to 8.02 microplastics per gram, suggesting that some shoreline areas have highly elevated concentrations linked to local sources. To put this in context, some of our nearshore samples were more contaminated than some spots on Lake Ontario.
In comparison, samples from deep-water sections of our lake range from 0 to 1.28 microplastics per gram. This is lower than the Muskoka results, suggesting that Kasshabog has a comparatively cleaner background level of microplastics despite some hotspots.
Sampling both deep-water and nearshore sediments is important because they address different questions. Deep-water sediment shows long-term average accumulation across the lake, while nearshore sediment samples identify hotspots from local sources.
