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

Recent 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 colo...

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Other Authors: McLoughlin, Philip D.
Language:English
Published: 2013
Subjects:
Online Access:http://hdl.handle.net/10388/ETD-2013-10-1182
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spelling ndltd-USASK-oai-ecommons.usask.ca-10388-ETD-2013-10-11822013-09-07T04:02:45ZSea-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 horsesisoscapestable isotopenutrient transfertrophic enrichmentnutrient cyclingnitrogen isotopeSable Island horsegrey sealternnitrogenbiogenic vectormarine-derivedkrigingnutrient gatewayRecent 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.McLoughlin, Philip D.Hobson, Keith A.2013-09-06T12:00:18Z2013-09-06T12:00:18Z2013-102013-09-05October 2013textthesishttp://hdl.handle.net/10388/ETD-2013-10-1182eng
collection NDLTD
language English
sources NDLTD
topic isoscape
stable isotope
nutrient transfer
trophic enrichment
nutrient cycling
nitrogen isotope
Sable Island horse
grey seal
tern
nitrogen
biogenic vector
marine-derived
kriging
nutrient gateway
spellingShingle isoscape
stable isotope
nutrient transfer
trophic enrichment
nutrient cycling
nitrogen isotope
Sable Island horse
grey seal
tern
nitrogen
biogenic vector
marine-derived
kriging
nutrient gateway
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
description Recent 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.
author2 McLoughlin, Philip D.
author_facet McLoughlin, Philip D.
title 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
title_short 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
title_full 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
title_fullStr 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
title_full_unstemmed 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
title_sort 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
publishDate 2013
url http://hdl.handle.net/10388/ETD-2013-10-1182
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