LE3 .A278 2020

2020

Mallory, Mark

Acadia University

Bachelor of Science

Honours

Biology

Biology

Plastic pollution is increasingly recognized as one of the most significant environmental concerns in the modern era. Organisms in marine environments are particularly susceptible to effects of plastic pollution via ingestion, entanglement, and toxicity. Seabirds are useful bioindicators of ongoing issues in marine systems, and they can be studied to learn more about how pollutants move throughout an ecosystem. I studied gut contents of 44 herring gulls (Larus argentatus), and 44 great black-backed gulls (L. marinus) to compare ingested plastic and other anthropogenic debris between species, with respect to their average trophic feeding positions (based on stable isotopes of nitrogen and carbon) and time of year. Although great black-backed gulls fed predictably at a higher trophic level, there were no differences in ingestion rates, plastic mass, or seasonal ingestion of plastics between species. I interpret these results as suggesting, first, that herring gulls rely more heavily on low trophic level landfill food subsidies during the winter (leftover food scraps), and shift to more natural higher trophic level marine foods (e.g., invertebrates, scavenging fisheries wastes) in the breeding period. Second, I interpret great black-backed gulls to be more likely feeding on more on natural foods (or directly scavenging fisheries by-products) throughout the year, while incorporating items from the landfill as a supplementary source of food. Finally, I comment on the need for more standardized methods in the field of plastic ingestion research and compare my findings to those in other literature.

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https://scholar.acadiau.ca/islandora/object/theses:3361