Plastic fibers have been shown to account for 71% of microplastic particles in surface water samples from Great Lakes tributaries even though previous studies indicated that samples collected from the lake surface in the offshore Great Lakes environment contained only 1-14% fibers.
The questions of why the surface of Lakes had so few fibers compared to tributaries and where these fibers were ultimately transported in the Lakes is answered by a recent study of benthic sediment in Lake Michigan and Lake Erie.
This latest publication is the third in a series of publications designed to understand microplastics in tributaries and their fate after they enter the Great Lakes. Combined, the studies indicate that plastic fibers such as polyester, rayon, nylon, and cellulose acetate are suspended in the in the water column of rivers due to turbulent flows, but settle out and are deposited in bottom sediments when the rivers flow into the more quiescent Great Lakes.
- Plastic Debris in 29 Great Lakes Tributaries: Relations to Watershed Attributes and Hydrology
This study, supported by the GLRI and published in 2016, concluded that 71% of microplastic particles in these tributaries were fibers. This was unexpected, given that previous studies of offshore Great Lakes that sampled just the top 16 cm of water found between 1% and 14% of microplastic particles were fibers. This left an important unanswered question: Where do the fibers go once discharged into the lakes?
- Vertical Distribution of Microplastics in the Water Column and Surficial Sediment from the Milwaukee River Basin to Lake Michigan
For this study, supported by the Milwaukee Metropolitan Sewerage District and published in 2019, water was sampled at the surface, several points in the water column, and in the sediments in both the Milwaukee River and in the lakebed offshore of Milwaukee. Plastic fiber particles were abundant in the water column and in the sediment.
- Spatial Distribution of Microplastics in Surficial Benthic Sediment of Lake Michigan and Lake Erie
For this study, published in 2020 and supported by the GLRI, Lake sediments were sampled throughout Lake Michigan and Lake Erie. Particles were detected in all samples, and fibers were the most abundant particle type in these sediment samples. Most particles observed in these samples were negatively buoyant. Concentrations of microplastics in Lake Erie sediment samples were 6 times greater than concentrations in Lake Michigan samples on average.