Date of Award

8-2024

Document Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Sciences and Technology

First Advisor

Juanita Urban-Rich

Second Advisor

Stephanie Wood

Third Advisor

Amanda Tokash-Peters

Abstract

Due to their semi-aquatic lifestyle, pinnipeds are an ideal sentinel group used to study anthropogenic threats to the marine environment. Microplastics, primarily transported to the ocean through river discharge or weathering of larger plastics, are a threat to both pinnipeds and humans. Bioaccumulation of microplastics within the marine food web has been observed, with pinnipeds indirectly ingesting microplastics through their prey. As generalists, gray seals (Halichoerus grypus) are a pinniped species that can provide information on microplastic exposure to many lower trophic level organisms. This thesis explores the relationship between the diet and microplastic ingestion of gray seals on Great Point, Nantucket. Firstly, gray seal diet was assessed using two methods, prey hard parts and DNA metabarcoding, from 112 scat samples. Our results support previous findings that DNA metabarcoding reduces the biases of prey hard parts, identifying more prey types in more samples. We then compared the DNA metabarcoding diet results to microplastic concentration, type, fiber color, and polymer type. Anthropogenic microparticles were found in 111 out of 112 gray seal scat samples. Our findings suggested weak relationships between the microplastic variables and diet, however our methods were not able to determine the abundance of each prey type, making it difficult to draw any real conclusions. More research using quantitative methods is needed to determine whether gray seals’ diet is influencing their microplastic consumption. Given their role as a sentinel species, gray seals, along with other pinnipeds, offer valuable insights into the distribution and impact of microplastics throughout their range. Future research should continue to utilize pinnipeds as indicators to further investigate microplastic pollution in marine ecosystems.

Comments

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Brown_shannon_MS_signaturepage.pdf (310 kB)

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