Anthropogenic subsidies and contaminant biotransport by herring gull (Larus argentatus) in southern Nova Scotia
LE3 .A278 2020
Master of Science
Seabirds can biotransport contaminants, moving them from marine to terrestrial environments around breeding colonies. This process can have marked impacts on receiving environments and biota. Generalist predators such as herring gulls (Larus argentatus) can exploit a wide range of natural and anthropogenic food items such as waste from fish processing or mink (Mustela vision) farms. The impact of gulls transporting contaminants from anthropogenically sourced food has not been assessed in southern Nova Scotia. To examine foraging patterns, GPS tags were deployed on herring gulls caught at breeding colonies in southern Nova Scotia in 2014, 2015 2018 and 2019. Gulls from all study colonies used anthropogenic food sources extensively. I measured total mercury (THg), persistent organic pollutants (POPs) and a suite of trace elements (TEs) in surface soils from gull colonies and nearby gull-free reference sites to determine if gulls were depositing contaminants from anthropogenic food sources. Additionally, I collected soil cores at different depths from gull colonies to examine deposition of these contaminants temporally. I found little evidence of gull or atmospheric deposition of contaminants through time in cores. I found a consistent THg biotransport signal, but local conditions and other seabird species also likely impact THg accumulation in soils. I also detected a signal of biotransport with respect to some TEs, including zinc and copper. In contrast I did not find that POPs were accumulating in soils at high concentrations. Overall, results suggest that highly mobile and scavenging gulls are biovectors for some contaminants likely derived from anthropogenic food sources and that generalist predators increase the environmental footprint of these industries that produce abundant waste.
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