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Southern Ocean isoscapes derived from a wide-ranging circumpolar marine predator, the Antarctic fur seal

Citation

Walters, A and Hindell, M and Goebel, ME and Bester, MN and Trathan, PN and Oosthuizen, WC and Lea, M-A, Southern Ocean isoscapes derived from a wide-ranging circumpolar marine predator, the Antarctic fur seal, Ecological Indicators, 118 Article 106694. ISSN 1470-160X (2020) [Refereed Article]

Copyright Statement

2020 Elsevier Ltd. All rights reserved.

DOI: doi:10.1016/j.ecolind.2020.106694

Abstract

The large-scale spatial patterns and primary drivers of food web dynamics across seascapes can be investigated using isotope ratios in marine consumers. However, interpreting complex signatures from mobile animals can require good knowledge of spatial isotopic variations in the environment. This is particularly true in the Southern Ocean where regional differences in the physical environment affect habitat predictability and predator foraging. We applied a retrospective-isotope approach integrated with tracking locations for a model species, the Antarctic fur seal (Arctocephalus gazella), to generate large-scale spatially-explicit predictions of isotopic gradients ("isoscapes") across the Southern Ocean. Vibrissae and blood samples were collected during post- and pre-breeding periods from both Antarctic and sub-Antarctic breeding environments. Stable isotope values from vibrissae growth and serially sampled blood enabled the reconstruction of an isotopic time-series that could be directly related to feeding locations at sea. Tracked seals were widely distributed in the southern Atlantic and Indian Oceans, with important foraging activity centred on productive upwelling areas, oceanic frontal zones and shelf environments. Corresponding seal δ13C and δ15N values were positively correlated to the Southern Ocean latitudes at which the tracked individuals foraged. Breeding site, bi-monthly foraging period and foraging location all explained significant variation in isotopic values during migration. Isotopic variation was largely driven by the latitudinal and inshore/offshore gradient in δ13C and δ15N at the base of the food web in neritic and oceanic waters. These delineate the spatio-temporal isotopic variability of important foraging habitats, providing a valuable perspective on the spatial and seasonal distribution of predators and forage availability. Differences in inferred predator distribution within and between breeding locations have implications for relative exposure to anthropogenic threats from fisheries interactions and climate change. This study demonstrates that isotope tracers in archival tissues are useful indicators of resource partitioning by marine consumers to directly inform spatial conservation planning and ecosystem management strategies at the cross-basin scale.

Item Details

Item Type:Refereed Article
Keywords:fur seal, foraging, stable isotopes, archival tissues, connectivity patterns, Southern Ocean, isoscapes, pinniped, marine predators, spatial distribution
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological oceanography
Objective Division:Environmental Management
Objective Group:Terrestrial systems and management
Objective Field:Assessment and management of terrestrial ecosystems
UTAS Author:Walters, A (Dr Andrea Walters)
UTAS Author:Hindell, M (Professor Mark Hindell)
UTAS Author:Lea, M-A (Professor Mary-Anne Lea)
ID Code:140608
Year Published:2020
Funding Support:Australian Research Council (DP0770910)
Web of Science® Times Cited:1
Deposited By:Ecology and Biodiversity
Deposited On:2020-08-31
Last Modified:2021-02-11
Downloads:0

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