Nitrogen Fuelling of the Pelagic Food Web of the Tropical Atlantic - Université Pierre et Marie Curie Accéder directement au contenu
Article Dans Une Revue PLoS ONE Année : 2015

Nitrogen Fuelling of the Pelagic Food Web of the Tropical Atlantic

Résumé

We estimated the relative contribution of atmosphere (ic Nitrogen (N) input (wet and dry deposition and N fixation) to the epipelagic food web by measuring N isotopes of different functional groups of epipelagic zooplankton along 23°W (17°N-4°S) and 18°N (20-24°W) in the Eastern Tropical Atlantic. Results were related to water column observations of nutrient distribution and vertical diffusive flux as well as colony abundance of Trichodesmium obtained with an Underwater Vision Profiler (UVP5). The thickness and depth of the nitracline and phosphocline proved to be significant predictors of zooplankton stable N isotope values. Atmospheric N input was highest (61% of total N) in the strongly stratified and oligotrophic region between 3 and 7°N, which featured very high depth-integrated Trichodesmium abundance (up to 9.4×104 colonies m-2), strong thermohaline stratification and low zooplankton δ15N (~2‰). Relative atmospheric N input was lowest south of the equatorial upwelling between 3 and 5°S (27%). Values in the Guinea Dome region and north of Cape Verde ranged between 45 and 50%, respectively. The microstructure-derived estimate of the vertical diffusive N flux in the equatorial region was about one order of magnitude higher than in any other area (approximately 8 mmol m-2 d 1). At the same time, this region received considerable atmospheric N input (35% of total). In general, zooplankton δ15N and Trichodesmium abundance were closely correlated, indicating that N fixation is the major source of atmospheric N input. Although Trichodesmium is not the only N fixing organism, its abundance can be used with high confidence to estimate the relative atmospheric N input in the tropical Atlantic (r2 = 0.95). Estimates of absolute N fixation rates are two- to tenfold higher than incubation-derived rates reported for the same regions. Our approach integrates over large spatial and temporal scales and also quantifies fixed N released as dissolved inorganic and organic N. In a global analysis, it may thus help to close the gap in oceanic N budgets.
Fichier principal
Vignette du fichier
journal.pone.0131258.pdf (1.31 Mo) Télécharger le fichier
Origine : Publication financée par une institution
Loading...

Dates et versions

hal-01308142 , version 1 (27-04-2016)

Licence

Paternité

Identifiants

Citer

Vera Sandel, Rainer Kiko, Peter Brandt, Marcus Dengler, Lars Stemmann, et al.. Nitrogen Fuelling of the Pelagic Food Web of the Tropical Atlantic. PLoS ONE, 2015, 10 (6), pp.e0131258. ⟨10.1371/journal.pone.0131258.s003⟩. ⟨hal-01308142⟩
826 Consultations
606 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More