LE3 .A278 2020

2020

O'Driscoll, Nelson

Acadia University

Bachelor of Science

Honours

Environmental Science

Earth & Environmental Sciences

Biovectors are organisms that can transport contaminants and nutrients to remote locations through excretion, moulting and decomposition of carcasses. Herring gulls (Larus argentatus) are typically top predators of aquatic systems, which increases their exposure to methylmercury through biomagnification. Methylmercury is known for its neurotoxicity and estrogenic effects on organisms. Big Meadow Bog on Brier Island is the summer (May-August) nesting site for ~6000 herring gulls (Larus argentatus). In order to obtain unaffected guano samples, five plastic posts were deployed in the most populated areas of the bog for birds to perch and excrete on. Guano samples were collected every two weeks in summer; totalling 10 sampling trips over two years. A total of 43 guano samples were dried, homogenized and analyzed for total mercury, extractable phosphate and sulphate. This study demonstrated gulls were depositing THg and considerable PO43-throughout their nesting season. It also highlighted that there was a significant decreasing trend of THg from May through September, which suggests that gulls were potentially switching to aquatic food sources when their young hatched . This would contribute to increased THg values in their guano at the start of their nesting period. I suggest that analysing MeHg, in tandem with THg, would provide more insights into the movement and metabolism of nutrients and contaminants within seabirds.

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https://scholar.acadiau.ca/islandora/object/theses:3392