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A critical assessment of marine predator isoscapes within the southern Indian Ocean.

ABSTRACT: Background:Precise and accurate retrospective geolocation of marine predators via their tissues' isotopic composition relies on quality reference maps of relevant isotopic gradients ("isoscapes"). Additionally, a good working knowledge of any discrimination factors that may offset a marine predator's isotopic composition from baseline isotopic values, as well as tissue specific retention rates, are imperative. We provide a critical assessment of inter-specific differences among marine predator-level isoscapes within the Indian Sector of the Southern Ocean. Methods:We combined fine-scale GPS tracking data and concurrent blood plasma ?13C and ?15N values of eight seabird species (three albatross, two giant petrel and three penguin species) breeding at Marion Island to produce species- and guild-specific isoscapes. Results:Overall, our study revealed latitudinal spatial gradients in both ?13C and ?15N for far-ranging seabirds (albatrosses and giant petrels) as well as inshore-offshore gradients for near-ranging seabirds (penguins). However, at the species level, latitudinal spatial gradients were not reflected in the ?13C and ?15N isoscapes of two and three, respectively, of the five far-ranging species studied. It is therefore important when possible to estimate and apply species-specific isoscapes or have a good understanding of any factors and pathways affecting marine predators' isotopic composition when estimating the foraging distribution of marine predators via their tissues' stable isotope compositions. Conclusions:Using a multi-species approach, we provide evidence of large and regional scale systematic spatial variability of ?13C and ?15N at the base of the marine food web that propagates through trophic levels and is reflected in the isotopic composition of top predators' tissues.

SUBMITTER: Carpenter-Kling T

PROVIDER: S-EPMC7322845 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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A critical assessment of marine predator isoscapes within the southern Indian Ocean.

Carpenter-Kling Tegan T Pistorius Pierre P Reisinger Ryan R Cherel Yves Y Connan Maëlle M

Movement ecology 20200629

<h4>Background</h4>Precise and accurate retrospective geolocation of marine predators via their tissues' isotopic composition relies on quality reference maps of relevant isotopic gradients ("isoscapes"). Additionally, a good working knowledge of any discrimination factors that may offset a marine predator's isotopic composition from baseline isotopic values, as well as tissue specific retention rates, are imperative. We provide a critical assessment of inter-specific differences among marine pr ...[more]

PMID: 32612836

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Project description:Development in foraging behaviour and dietary intake of many vertebrates are age-structured. Differences in feeding ecology may correlate with ontogenetic shifts in dispersal patterns, and therefore affect foraging habitat and resource utilization. Such life-history traits have important implications in interpreting tropho-dynamic linkages. Stable isotope ratios in the whiskers of sub-yearling southern elephant seals (Mirounga leonina; n = 12) were used, in conjunction with satellite telemetry and environmental data, to examine their foraging habitat and diet during their first foraging migration. The trophic position of seals from Macquarie Island (54°30'S, 158°57'E) was estimated using stable carbon (δ(1) (3)C) and nitrogen (δ(15)N) ratios along the length of the whisker, which provided a temporal record of prey intake. Satellite-relayed data loggers provided details on seal movement patterns, which were related to isotopic concentrations along the whisker. Animals fed in waters south of the Polar Front (>60°S) or within Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Statistical Subareas 88.1 and 88.2, as indicated by both their depleted δ(1) (3)C (<-20‰) values, and tracking data. They predominantly exploited varying proportions of mesopelagic fish and squid, and crustaceans, such as euphausiids, which have not been reported as a prey item for this species. Comparison of isotopic data between sub-yearlings, and 1, 2 and 3 yr olds indicated that sub-yearlings, limited by their size, dive capabilities and prey capture skills to feeding higher in the water column, fed at a lower trophic level than older seals. This is consistent with the consumption of euphausiids and most probably, Antarctic krill (Euphausia superba), which constitute an abundant, easily accessible source of prey in water masses used by this age class of seals. Isotopic assessment and concurrent tracking of seals are successfully used here to identify ontogenetic shifts in broad-scale foraging habitat use and diet preferences in a highly migratory predator.

Dataset Information

A critical assessment of marine predator isoscapes within the southern Indian Ocean.

Publications

A critical assessment of marine predator isoscapes within the southern Indian Ocean.

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