Portland State University. Earth, Environment, & Society Ph. D. Program
Term of Graduation
Date of Publication
Doctor of Philosophy (Ph.D.) in Earth, Environment, & Society
Earth, Environment, & Society
Microplastics -- Environmental aspects -- Pacific Northwest, Shellfish as food -- Contamination -- Pacific Northwest, Pacific oyster, Pacific razor clam, Bivalves -- Exhibitions, Waste minimization -- Public opinion, Plastic scrap -- Public opinion, Plastic marine debris -- Environmental aspects
1 online resource (xvi, 191 pages)
Up to 23 million metric tons of mismanaged plastics enter the global ocean annually. Microplastics (MPs;<5mm) degrading. MPs leak into the environment and now pervade every corner of the earth, with implications for animal, plant, ecosystem and human health. It is important to understand localized environmental MP prevalence, distribution and organismal uptake in order to determine the extent of MP pollution, and ultimately unlock solution sets to reduce transmission of MPs into the natural world. In Chapter 2, I quantified MP types, concentrations, anatomical burdens, geographic distribution, and temporal differences in Pacific oysters (Crassostrea gigas) and Pacific razor clams (Siliqua patula) from 15 coastal sites in Oregon. Both of these species are integral to culture, economy, gastronomy and food security along the United States West Coast. In Chapter 3, I quantified MPs in Pacific razor clams collected from 8 Olympic Coast, Washington sites, administered questionnaires to recreational razor clammers and subsequently estimated annual MP exposure of those Olympic Coast razor clam harvester-consumers surveyed. In Chapter 4, I designed and installed an educational ocean plastic exhibit at the OR Coast Aquarium. I evaluated time spent in the exhibit, number of times panels were read or interactive elements were touched, determined current and intended single-use plastic reduction and plastic stewardship actions by visitor demographic, gauged visitor learning after the exhibit experience and recorded suggestions for exhibit improvement.
MPs were present in Pacific oysters and razor clams from all 23 (15 OR and 8 WA) sites studied in Chapters 2 and 3. Among all clams and oysters studied in both OR and WA, over 99% of MPs encountered were fibers. In OR bivalves, whole oysters and razor clams contained an average of 10.95 ± 0.77 and 8.84 ± 0.45 MP pieces per individual, or 0.35 ± 0.04 and 0.16 ± 0.02 MP g-1 tissue, respectively. Spring-collected oysters contained more MPs than summer-collected oysters. In WA razor clams, average MP burden for whole clams was 6.75 ± 0.60 MP/individual and for cleaned clams (rinsed with guts and gills removed) was 3.44 ± 0.25 MP/individual.
The number of razor clams consumed per meal by WA razor clam harvesters was 4.27 ± 0.27, which varied by gender and ethnicity, but not income or age. Harvesters ate 0-209 meals/year of razor clams, and 88.3% of respondents fully cleaned razor clams before consuming them. Annual suspected MP exposure for razor clam harvester-consumers was 60-3,070 pieces for cleaned and 120-6,020 for whole clams.
Within our OR Coast Aquarium ocean plastic exhibit, childre touched the three interactive podia more than adults and adults read informational panels more frequently than children. Adult visitors increased their desire to help address the ocean plastic problem after interaction with our exhibit and reported willingness to change one or more of the single-use plastic or plastic stewardship actions, with nearly 40% intending to increase use of reusable straws and contribute to cleaning the beach. Of all age groups, 18-29 year olds had the highest change in desire to help address the ocean plastic problem before and after seeing the exhibit, but the lowest likelihood of engaging in single-use plastic reduction or plastic stewardship actions, highlighting a need for targeted outreach to this specific age group. The totality of all three research chapters within this dissertation serve as important references within the growing portfolio of Pacific Northwest MP investigations, and can inform future education, outreach and policy efforts to attenuate environmental MPs and reduce household-level single-use plastic waste generation in the region.
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Baechler, Britta Rahel, "Microplastics in Pacific Northwest Bivalves: Ecological Prevalence, Harvester-Consumer Exposure, and Aquarium Exhibit Outcomes" (2020). Dissertations and Theses. Paper 5616.
Available for download on Tuesday, November 30, 2021