The vast majority of theses in this collection are open access and freely available. There are a small number of theses that have access restricted to the WWU campus. For off-campus access to a thesis labeled "Campus Only Access," please log in here with your WWU universal ID, or talk to your librarian about requesting the restricted thesis through interlibrary loan.
Date Permissions Signed
Date of Award
Department or Program Affiliation
Master of Science (MS)
Sofield, Ruth M.
Bingham, Brian L. 1960-
Spanjer, Andrew R.
Microplastics have become ubiquitous in the environment and have been intensively studied in recent years. Researchers have documented several toxic effects to aquatic organisms, but the role of different microplastic properties in the toxic responses is not well understood. Toxic effects can be altered by the microplastic pieces themselves, by chemicals from the microplastics, and by sorbed environmental organic or metal pollutants, which microplastics concentrate and transport. I decided to focus on the chemical aspect of microplastic toxicity by observing responses of a marine invertebrate when exposed to several types of leachate solutions, created by soaking microplastics in seawater for 48 hours. Juvenile mysids (Americamysis bahia) were exposed to various types of polystyrene (PS), polyethylene terephthalate (PET), polycarbonate (PC), polyester, and polyacrylonitrile microplastic leachates for 4 days and mortality was recorded. Toxicity tests were also performed on environmentally aged versions of each leachate, which were created using microplastics deployed in Bellingham Bay for 70-76 days. I used log-logistic models to model concentration-response relationships and determined the concentration of leachate that results in 50% mortality (the LC50). LC50 values were compared with log-likelihood ratios to determine significant differences between leachate types and aging conditions. Non-aged and aged versions of the PS, PET, and PC leachates caused no significant mortality at concentrations as high as 100 grams per liter. All types of non-aged microplastic fiber leachates caused mysid mortality, with red polyacrylonitrile being the most toxic, followed by green polyester and white polyester. In contrast, all three of the same fiber leachates that were aged caused no mortality at concentrations as high as 50 grams per liter, suggesting that the acute toxicity of microplastic fibers decreases after being subject to environmental processes. Chemical analysis of the fiber leachate types was performed with LC-QTOF-MS, and it shows unique chemical features differentiating the toxic leachates (created from non-aged fibers) and the non-toxic leachates (created from aged fibers). My results have important implications for future microplastic toxicity studies and regulations on plastic debris, suggesting more study of microplastic fibers is warranted, and the role of chemicals in microplastic toxicity needs consideration in addition to physical hazards of microplastic ingestion.
microplastics, environmental aging, microplastic leachate, microplastic fibers, mysid shrimp
Western Washington University
Subject – LCSH
Microplastics--Toxicity testing; Marine pollution; Mysidae--Effect of pollution on
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Johnson, Allie, "Effects of Environmental Aging on the Acute Toxicity and Chemical Composition of Various Microplastic Leachates" (2021). WWU Graduate School Collection. 1064.