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Marine Ecology Progress Series

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MEPS 417:277-285 (2010)  -  DOI:

Stable isotope variation in loggerhead turtles reveals Pacific–Atlantic oceanographic differences

Mariela Pajuelo1,*, Karen A. Bjorndal1, Joanna Alfaro-Shigueto2,3, Jeffrey A. Seminoff4, Jeffrey C. Mangel2,3, Alan B. Bolten1

1Archie Carr Center for Sea Turtle Research, Department of Biology, University of Florida, Gainesville, Florida 32611, USA
2Pro Delphinus, Octavio Bernal 572-5, Lima 11, Peru
3Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus, Penryn, Cornwall TR10 9EZ, UK
4NOAA-National Marine Fisheries Service, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, California 92037, USA

ABSTRACT: Denitrification and nitrogen-fixation processes in the marine environment have been intensively studied, particularly how these processes affect the nitrogen stable-isotope signature (δ15N) of inorganic nutrients and organisms at the base of the food web. However, the assumption that these δ15N differences at the base of food webs are reflected in higher trophic-level organisms has not been widely investigated. In the present study, we evaluated whether an ocean-basin δ15N variation was evident in oceanic juvenile loggerhead turtles Caretta caretta by analyzing their stable-isotope signatures in the Pacific and Atlantic oceans. Skin samples from oceanic juvenile loggerheads were collected from Peruvian waters in the southeast Pacific and from waters around the Azores Archipelago in the northeast Atlantic and analyzed for δ15N and carbon stable-isotope signature (δ13C). Our results showed that turtles in the 2 ocean regions have mean δ13C signatures of –16.3 and –16.7‰, which reflects the oceanic feeding behavior of these loggerhead populations. However, the δ15N signatures in Pacific loggerheads are significantly higher (mean ± SD = 17.1 ± 0.9‰) than those of Atlantic loggerheads (7.6 ± 0.5‰). This inter-ocean difference in δ15N values was also observed in organisms at the base of the food web in the 2 study areas. The δ15N at the base of the food web, which is determined by the predominant process of the nitrogen cycle in each ocean region, is subsequently transferred to higher trophic levels. Stable isotope signatures in high trophic-level organisms, such as oceanic-stage sea turtles, can reveal differences in oceanographic processes.

KEY WORDS: Stable isotopes · δ15N · δ13C · Loggerhead turtles · Nitrogen fixation · Denitrification · Southeast Pacific · Northeast Atlantic

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Cite this article as: Pajuelo M, Bjorndal KA, Alfaro-Shigueto J, Seminoff JA, Mangel JC, Bolten AB (2010) Stable isotope variation in loggerhead turtles reveals Pacific–Atlantic oceanographic differences. Mar Ecol Prog Ser 417:277-285.

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