Author Type

Graduate Student

Date of Award

Summer 7-27-2026

Document Type

Dissertation

Publication Status

Version of Record

Submission Date

August 2026

Department

Biological Sciences

College Granting Degree

Charles E. Schmidt College of Science

Department Granting Degree

Biological Sciences

Degree Name

Doctor of Philosophy (PhD)

Thesis/Dissertation Advisor [Chair]

Sarah Milton

Abstract

Over the years, plastic production has increased to astonishing numbers and is predicted to continue. Over time, environmental plastic will degrade into smaller pieces, which sea turtles can mistake for prey. Chemicals associated with plastics have been identified in tissues of sea turtles, and some are suspected to be endocrine disruptors. Sea turtles are known to ingest plastics, but more information is needed to illuminate the potential physiological impacts plastic chemicals may have on sea turtles. This study compared plastic ingestion and toxicant levels across species and ontogenically, as different species and life stages inhabit different areas which will influence exposure and thus risk. Sea turtle ingestion of plastic was investigated by collecting contents from the gastrointestinal (GI) tract of freshly euthanized or dead sea turtle carcasses. The plastic was collected, categorized and identified using attenuated total reflectance (ATR) with Fourier-transform infrared (FTIR) spectrometry. To determine actual exposure, gas chromatography was used to analyze sea turtle liver, adipose, and gonadal tissues for known chemicals associated with plastics. As the potential for plastic leachates to interfere with reproduction has not been investigated in sea turtles, male and female sea turtle gonads were used to conduct competitive binding analyses to identify potential endocrine disruptors. Out of 180 turtles collected, 91 (51%) had plastic in their GI tract. White and clear plastic were the most common colors recovered, and polypropylene and polyethylene were the two most common polymers recovered. Dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP), chemicals that may leach from plastics, were both found in liver, fat and gonadal tissues. Gonadal tissue had higher DEHP concentrations than fat and liver tissue. Decabromodiphenyl ether (decaBDE), bisphenol A (BPA), DBP, and DEHP all showed binding in male and female gonadal tissue. My results suggest that washbacks and juvenile sea turtles are the most susceptible to the physiological impacts of plastics: mortality, chemicals sequestered in tissues, and binding disruption were highest in these size classes. This study gives insight as to how plastic is impacting these threatened species and suggests a need for better management strategies to protect the health of the environment.

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