Trophic Ecology of Atlantic Bluefin Tuna (Thunnusthynnus) Larvae from the Gulf of Mexico and NW Mediterranean Spawning Grounds: A Comparative Stable Isotope Study

The present study uses stable isotopes of nitrogen and carbon (δNandδC) as trophic indicators for Atlantic bluefin tuna larvae (BFT) (6–10mm standard length) in the highly contrasting environmental conditions of the Gulf of Mexico (GOM) and the Balearic Sea (MED). These regions are differentiated by their temperature regime and relative productivity, with the GOM being significantly warmer and more productive. MED BFT larvae showed the highest δN signatures, implying an elevated trophic position above the underlying microzooplankton baseline. Ontogenetic dietary shifts were observed in the BFT larvae from the GOM and MED which indicates early life trophodynamics differences between these spawning habitats. Significant trophic differences between the GOM andMED larvae were observed in relation to δN signatures in favour of the MED larvae, which may have important implications in their growth during their early life stages.These low δN levels in the zooplankton from the GOMmay be an indication of a shifting isotopic baseline in pelagic food webs due to diatrophic inputs by cyanobacteria. Lack of enrichment for δN in BFT larvae compared to zooplankton implies an alternative grazing pathway from the traditional food chain of phytoplankton—zooplankton—larval fish. Results provide insight for a comparative characterization of the trophic pathways variability of the two main spawning grounds for BFT larvae. PLOS ONE | DOI:10.1371/journal.pone.0133406 July 30, 2015 1 / 22 OPEN ACCESS Citation: Laiz-Carrión R, Gerard T, Uriarte A, Malca E, Quintanilla JM, Muhling BA, et al. (2015) Trophic Ecology of Atlantic Bluefin Tuna (Thunnusthynnus) Larvae from the Gulf of Mexico and NW Mediterranean Spawning Grounds: A Comparative Stable Isotope Study. PLoS ONE 10(7): e0133406. doi:10.1371/journal.pone.0133406 Editor: Athanassios C. Tsikliras, Aristotle University of Thessaloniki, GREECE Received: April 16, 2015 Accepted: June 26, 2015 Published: July 30, 2015 Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by CTM201129525-C04-02 grant project, “Assessment of the Atlantic bluefin TunA population breeding in the western MEditerranean (ATAME)”, funded by the Spanish Ministry of Science and Innovation and grant# 13BTRP009 to BM, "Accounting for the Influence of Feeding Success on the Growth and Survival of Bluefin Tuna Larvae in Stock Assessment Efforts" founded by National Oceanic and