Rayon is the Predominant Microfiber in Zebra Mussels (Dreissena polymorpha) from a North American Lake in the Context of a Global Analysis of Bivalves

Abstract Microplastics and other anthropogenic particles are found in many bivalve species and present entry points for microplastic transfer into food webs. However, there have been relatively few studies of anthropogenic particle accumulation by bivalves in freshwater lakes. We measured anthropogenic particle quantity, size, and polymer-type in zebra mussels ( Dreissena polymorpha ) and in the water column of a North American lake (Lake Winnebago, Wisconsin). Our objectives were to: 1) Characterize anthropogenic particle accumulation in zebra mussels and in lake water and, 2) Conduct a global, quantitative analysis of the polymer types of anthropogenic particles in bivalves in aquatic ecosystems. We collected zebra mussels and water column samples in Lake Winnebago from June through August 2021 and used Fourier-Transform Infrared Spectroscopy (FTIR) to measure the composition of microplastics and other anthropogenic particles. Mean abundance of anthropogenic particles in zebra mussels and in the water column of Lake Winnebago was 7.9 anthropogenic particles / g soft tissue dry mass and 303 anthropogenic particles / m 3 respectively. The most abundant polymers in zebra mussels were rayon, cellulose, and polyester. Based on our global analysis, polyester (21% mean relative abundance), polyethylene (19%), and polypropylene (14%) were the most abundant microplastic polymers in bivalves. However, modified cellulose (12%), including rayon and cellophane, and cellulosic material (22%) were commonly found in bivalve tissue. Modified cellulose may be underreported in studies of anthropogenic particles in bivalves, because of an emphasis on fully synthetic plastic polymers in many studies.