Baseline Analysis of Microplastics in Remote Boreal Lake Sediments at the Experimental Lakes Area
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Microplastics have become a contaminant of emerging concern because they have been characterized as a ubiquitous and persistent pollutant. At < 5mm in size, these particles have proven to generate a multitude of physical and chemical effects in organisms at varying trophic levels. However, there have been few baseline studies examining long-term microplastic pollution trends in remote boreal lakes. In the present study, we sought to determine the difference in microplastic abundances between recently deposited surface (depth = 0-5 cm) sediments and pre-industrially deposited deep (depth = 30-35 cm) sediments in Lake 378 and Lake 373 at the International Institute for Sustainable Development-Experimental Lakes Area in Northwestern Ontario. We collected three replicate sediment cores per lake and sectioned cores to collect recent and pre-industrial sediment samples from each. Laboratory analysis was then conducted to extract particles from sediment samples, before counting, measuring and visually categorizing them by shape and color. Mean particle abundances in recently deposited sediments were not significantly different from pre-industrial sediments in Lake 378 (p = 0.151) and Lake 373 (p = 0.376). There were also no significant differences between the mean sizes of particles in recently and pre-industrially deposited sediments for both Lake 378 (p = 0.961) and Lake 373 (p = 1.000). In Lake 378 and Lake 373 the highest percent abundances of recovered particle shapes in recent sediments were fragments and fibers, while pre-industrial sediments were largely composed of fibers. No notable differences were observed in the colors of the recovered particles from recent and pre-industrial sediments for both lakes. Based on the results of this study, recently deposited sediments do not show significant differences in abundance and particle characterization from pre-industrially deposited sediment. Further investigation through the chemical analysis of recovered particles is needed to confirm these findings.