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Sea-to-land nutrient transfer by seals and seabirds on Sable Island : isoscapes revealed by stable isotope analysis of vegetation with an echo in the island's feral horses

dc.contributor.advisorMcLoughlin, Philip D.en_US
dc.contributor.advisorHobson, Keith A.en_US
dc.contributor.committeeMemberBowen, W. Donen_US
dc.contributor.committeeMemberLamb, Eric G.en_US
dc.creatorLysak, Kentonen_US
dc.date.accessioned2013-09-06T12:00:18Z
dc.date.available2013-09-06T12:00:18Z
dc.date.created2013-10en_US
dc.date.issued2013-09-05en_US
dc.date.submittedOctober 2013en_US
dc.description.abstractRecent research using stable isotope analysis has shown a dependence on migrating or breeding populations of vertebrates as vectors for the transfer of marine-derived nutrients within coastal ecosystems. Sable Island, Nova Scotia, Canada supports numerous species of plants, a variety of seabird colonies (including common [Sterna hirundo] and Arctic [Sterna paradisaea] terns), the world’s largest grey seal (Halichoerus grypus) breeding colony, and a self-sustaining population of wild (feral) horses (Equus ferus caballus). I hypothesize that nitrogen cycling within this island ecosystem is highly influenced by the input of nutrients from seals and seabirds (‘biogenic vectors’), affecting primary production and potentially stabilizing higher trophic levels (i.e., horses). To examine this relation I developed a spatially-explicit isoscape for Sable Island through stable isotope analysis of nitrogen (δ15N) in samples (n = 282) of marram grass (Ammophila breviligulata). I incorporated significant variables (i.e., distance to vector colony and distance to shoreline, r2 = 0.41) into the final parsimonious interpolation model using universal co-kriging techniques. The greatest 15N enrichment occurred within the tips and along the perimeter of the island, coinciding with greater densities of grey seals, while the lowest values occurred within the centre of the island. I then identified individual contributions of seal-, tern- and horse-mediated transfer of marine-derived nutrients inland. Marram grass exhibited higher δ15N within seal (μ = 7.5‰) and tern (μ = 5‰) colonies, while horses and biogeochemical processes (i.e., volatilization, ammonification, etc.) most likely contributed to the homogeneity within the centre of the island (μ = 3.6‰). Due to the higher densities, wider distribution, and greater 15N enrichment of marram tissues, grey seals appear to be the most important vector species while seabirds have a more localized effect. The greater availability of N within vector colonies supplemented the local vegetation community, contributing to greater vegetation cover within colony boundaries. This relation had secondary effects on the horse population, which showed correspondingly higher horse δ15N values within the tips of the island (δ15N + 1.6‰) due to consumption of 15N enriched forage. I conclude that biogenic vector species promote nutrient transfer by establishing nutrient gateways which indirectly cause cascading effects throughout the food web.en_US
dc.identifier.urihttp://hdl.handle.net/10388/ETD-2013-10-1182en_US
dc.language.isoengen_US
dc.subjectisoscapeen_US
dc.subjectstable isotopeen_US
dc.subjectnutrient transferen_US
dc.subjecttrophic enrichmenten_US
dc.subjectnutrient cyclingen_US
dc.subjectnitrogen isotopeen_US
dc.subjectSable Island horseen_US
dc.subjectgrey sealen_US
dc.subjectternen_US
dc.subjectnitrogenen_US
dc.subjectbiogenic vectoren_US
dc.subjectmarine-deriveden_US
dc.subjectkrigingen_US
dc.subjectnutrient gatewayen_US
dc.titleSea-to-land nutrient transfer by seals and seabirds on Sable Island : isoscapes revealed by stable isotope analysis of vegetation with an echo in the island's feral horsesen_US
dc.type.genreThesisen_US
dc.type.materialtexten_US
thesis.degree.departmentBiologyen_US
thesis.degree.disciplineBiologyen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Science (M.Sc.)en_US

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