A global meta-analysis of marine predator nitrogen stable isotopes : relationships between trophic structure and environmental conditions

2018

Article référencé dans le Web of Science WOS:000448647200004

Pethybridge H., Choy C. A., Logan J. M., Allain V., Lorrain Anne, Bodin Nathalie, Somes C. J., Young J., Ménard Frédéric, Langlais C., Duffy L., Hobday A. J., Kuhnert P., Fry B., Menkès Christophe, Olson R. J.

Global Ecology and Biogeography, 2018, 27 (9), p. 1043-1055 ISSN 1466-822X

Aim We examined potential environmental drivers of broad-scale spatial patterns in the trophic structure of marine ecosystems as represented by nitrogen stable isotopes in globally distributed marine predators. Additionally, we assessed the effects of spatial scale on the predictive capabilities of environmental variables. LocationTime periodGlobal oceans. 2000 to 2015. Major taxa studiedMethodsTunas: Thunnus albacares, Thunnus obesus, Thunnus alalunga. We undertook a global compilation and meta-analysis of the bulk nitrogen stable isotope ratios (N-15 values) of three tuna species (n=4,281). After adjusting for regional variations in baseline N-15 values using a global ocean biogeochemistry model, generalized additive mixed models were employed to infer global-scale oceanographic controls of trophic structure, using cosmopolitan tuna species as a model. ResultsMain conclusionsFor the three tuna species, variation in trophic position estimated using bulk N-15 values was largely explained by geographical location and the corresponding oxygen minimum layer depth. Tuna trophic positions declined in areas with reduced oxygen at depth. Food-chain length, as captured by maximum trophic position, was longer in areas of the western Pacific Ocean and shorter in the northern Atlantic and eastern Pacific Oceans. Trophic adaptability of the tuna predators, as indicated by intraspecific variability, was highest in the western and central Pacific Ocean and lowest in the northern Atlantic Ocean. Our analysis demonstrated that while tunas share similar functional trophic roles, deeper-foraging tuna species had higher trophic positions globally. The predictive capacity of environmental variables decreased at finer (regional) spatial scales. Our work suggests that habitat compression resulting from the predicted global expansion of oxygen minimum zones with ocean warming will impact the trophic structure of marine food webs and the corresponding foraging habits of marine predators. Spatial scale analyses highlighted the importance of representing differences in regional ecological dynamics in global-scale trophic and ecosystem models.

Sciences fondamentales / Techniques d'analyse et de recherche [020] ; Ecologie, systèmes aquatiques [036] ; Ressources halieutiques [040]

Fonds IRD [F B010074382]

fdi:010074382