Synthetic microfiber loads in green algae, Cladophora, in Lake Michigan and Lake Erie

Synthetic microfibers, a category of microplastics, have been found throughout surface waters distributed around the world. These microfiber polymers are, for the most part, denser than water and become submerged in water environments such as lakes. Thus, surface water samples likely do not accurately account for microfibers loads, which integrate into other areas of the aquatic environment. One ecological sink for synthetic microfibers may be submerged aquatic vegetation (e.g. Cladophora, a nuisance green alga). Throughout the Laurentian Great Lakes, Cladophora creates large areas of submerged biomass, which can potentially concentrate these microfibers. To quantify the loads of synthetic microfibers in Cladophora, algal samples were collected in 2018 from Lake Erie and Lake Michigan at different depths and months. The samples were cleaned to remove unwanted debris and processed, using H2O2/UV advanced oxidation, to eliminate natural fibers. The average load of synthetic microfibers in Lake Erie samples was 32,000 microfibers/kg (dw) and 34,000 microfibers/kg (dw) in Lake Michigan. These findings suggest that submerged vegetation such as Cladophora is an additional sink for synthetic microfibers introduced through waterways. Keywords: Microplastics, microfibers, surface water, Cladophora, Great Lakes