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

• Published in: Movement Ecology
• Main Authors: Carpenter-Kling, Tegan, Pistorius, Pierre, Reisinger, Ryan, Cherel, Yves, Connan, Maëlle
• Other Authors: National Research Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2020
• Subjects: Ecology, Evolution, Behavior and Systematics; Indian; Southern Ocean; Giant Petrel; Giant Petrels; Marion Island
• Online Access: http://dx.doi.org/10.1186/s40462-020-00208-8; https://link.springer.com/content/pdf/10.1186/s40462-020-00208-8.pdf; https://link.springer.com/article/10.1186/s40462-020-00208-8/fulltext.html

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 δ 13 C and δ 15 N 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 δ 13 C and δ 15 N 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 δ 13 C and δ 15 N 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 δ 13 C and δ 15 N at the base of the marine food web that propagates through trophic levels and is reflected in the isotopic composition of top predators’ tissues.