Quantifying the Size Fraction of Microplastic Debris in the Water Column of Western Lake Superior (2022-03-25)

Abstract

Plastic pollution is a widely acknowledged global problem that has various negative impacts on the environment. As of 2019, 9.2 billion tonnes of plastic have been produced, and roughly 80% of plastic has become waste. Poor waste management, combined with the designed durability of plastics, has allowed for pollution of plastic to exponentially accumulate in aquatic systems. Once in the environment, plastic debris can weather and break down into smaller particles known as micro- and nano-plastics. This work aims at quantifying the size fraction of microplastics at different depths in the water column of sites in Western Lake Superior. Samples were collected at four sites in May and August 2021 with both manta net trawls, which collect microplastics >333 ?m at the air-water interface, and McLane pumps fitted with 3 filter sizes (300, 100 and 50 ?m). Microplastics were detected with visual microscopy or FTIR microscopy, depending on the size class. Our research shows the water column to contain a quantifiable load of microplastic waste in Lake Superior, with an increasing abundance of microplastic particles with decreasing particle size. This is the first study to report size fractionation of microplastic within the water column of any Laurentian Great Lake, improving our understanding of the plastic pollution problem in the Great Lakes as size helps to determine uptake by biota and accessibility to remediation approaches.