Available at: https://digitalcommons.calpoly.edu/theses/3429
Date of Award
8-2026
Degree Name
MS in Biological Sciences
Department/Program
Biological Sciences
College
College of Science and Mathematics
Advisor
Nikki Adams
Advisor Department
Biological Sciences
Advisor College
College of Science and Mathematics
Abstract
Microplastics (MPs, plastic particles < 5 mm in size, with diverse compositions and shapes) are widespread in marine environments. One type of plastic, polyethylene, is a common polymer found in products such as plastic bags, disposable water bottles, and synthetic fibers and commonly degrades into MPs found in marine habitats. Multiple laboratories including ours have documented a high prevalence of microfibers (MFs) specifically in organisms and sediments in coastal environments. Therefore, we wanted to determine how prevalent MPs are in common coastal organisms and how microfibers specifically impact important biological processes such as reproduction in an important marine invertebrate, sea urchins. The California purple sea urchin (Strongylocentrotus purpuratus) is a model organism and ecological indicator species in California ecosystems, and have planktonic larvae that are highly sensitive to pollutants. The first objective of this study was to determine whether S. purpuratus located on the central coast of California harbored MPs in their tissues, where they were accumulated, and if certain nearshore versus offshore locations contained sea urchins with higher MP loads. Sea urchins were collected from Goleta Beach Pier, Cal Poly Pier, Santa Rosa Reef, and Quarry Cove in Montaña de Oro State Park. We quantified MPs from their coelomic fluid, gonadal tissue, and digestive tracts. Sea urchins from Quarry Cove and Santa Rosa Reef contained the highest concentrations of MPs and differed by tissue type (p < 0.001). MPs were found in all three tissue types, but highest in the coelomic fluid. The second objective of this study was to determine whether exposure of female sea urchins to polyethylene microfibers (PEMFs) produce carryover effects that alter offspring development. Adult females were exposed to 1 mm PEMFs under control (0 PEMFs per individual), low (50 PEMFs per individual), and high (100 PEMFs per individual) treatments for three months then spawned to assess impacts of MFs on reproduction and development. There was no significant difference in the volume of eggs spawned among sea urchins from different PEMF treatments (p>0.05). Development was assessed by observing fertilization, measuring timing of first cleavage and subsequent development, including timing to specific stages and overall morphology, every 24 hours for four days. Maternal exposure to PEMFs did not affect fertilization or early cleavage rates. However, exposure of mothers to PEMFs of low or high concentrations significantly reduced the proportion of embryos developing normally, indicating a negative relationship between PEMF exposure and developmental success (p < 0.05). Our results demonstrate MPs are accumulated in tissues in sea urchins such as gonadal tissue responsible for housing germline cells and PEMFs caused developmental abnormalities. Taken together, this study provides a better understanding of threats the sea urchin population faces in an increasingly rich microplastic environment.