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Auteur Aumont, O.; Maury, O.; Lefort, S.; Bopp, L.
Titre Evaluating the Potential Impacts of the Diurnal Vertical Migration by Marine Organisms on Marine Biogeochemistry Type Article scientifique
Année 2018 Publication Revue Abrégée Global Biogeochemical Cycles
Volume 32 Numéro 11 Pages 1622-1643
Mots-Clés ecosystem; ocean; biogeochemistry; export; carbon cycle; diurnal vertical migration
Résumé Diurnal vertical migration (DVM) of marine organisms is an ubiquitous phenomenon in the ocean that generates an active vertical transport of organic matter. However, the magnitude and consequences of this flux are largely unknown and are currently overlooked in ocean biogeochemical models. Here we present a global model of pelagic ecosystems based on the ocean biogeochemical model NEMO-PISCES that is fully coupled to the upper trophic levels model Apex Predators ECOSystem Model, which includes an explicit description of migrating organisms. Evaluation of the model behavior proved to be challenging due to the scarcity of suitable observations. Nevertheless, the model appears to be able to simulate approximately both the migration depth and the relative biomass of migrating organisms. About one third of the epipelagic biomass is predicted to perform DVM. The flux of carbon driven by DVM is estimated to be 1.05 ± 0.15 PgC/year, about 18% of the passive flux of carbon due to sinking particles at 150 m. Comparison with local studies suggests that the model captures the correct magnitude of this flux. Oxygen is decreased in the mesopelagic domain by about 5 mmol?m?3 relative to simulations of an ocean without DVM. Our study concludes that DVM drives a significant and very efficient flux of carbon to the mesopelagic domain, similar in magnitude to the transport of DOC. Relative to a model run without DVM, the consequences of this flux seem to be quite modest on oxygen, due to compensating effects between DVM and passive fluxes.
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ISSN 0886-6236 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2458
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Auteur Ayata, S.-D.; Irisson, J.-O.; Aubert, A.; Berline, L.; Dutay, J.-C.; Mayot, N.; Nieblas, A.-E.; D'Ortenzio, F.; Palmiéri, J.; Reygondeau, G.; Rossi, V.; Guieu, C.
Titre Regionalisation of the Mediterranean basin, a MERMEX synthesis Type Article scientifique
Année 2018 Publication Progress in Oceanography Revue Abrégée
Volume 163 Numéro Pages 7-20
Mots-Clés Mediterranean Sea; regionalisation; biogeochemistry; circulation; mesoscale features; epipelagic ocean; management; spatial planning
Résumé Regionalisation aims at delimiting provinces within which physical conditions, chemical properties, and biological communities are reasonably homogeneous. This article proposes a synthesis of the many recent regionalisations of the open-sea regions of the Mediterranean Sea. The nine studies considered here defined regions based on different, and sometimes complementary, criteria: dynamics of surface chlorophyll concentration, ocean currents, three-dimensional hydrological and biogeochemical properties, or the distribution of organisms. Although they identified different numbers and patterns of homogeneous regions, their compilation in the epipelagic zone identifies nine consensus frontiers, eleven consensus regions with relatively homogeneous conditions, and four heterogeneous regions with highly dynamical conditions. The consensus frontiers and regions are in agreement with well-known hydrodynamical features of the Mediterranean Sea, which constrain the distribution of hydrological and ecological variables. The heterogeneous regions are rather defined by intense mesoscale activity. The synthesis proposed here could constitute a reference step for management actions and spatial planning, such as the application of the European Marine Strategy Framework Directive, and for future biogeochemical and ecological studies in the Mediterranean Sea.
Adresse Center for Prototype Climate Modeling, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
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Editeur Elsevier BV Lieu de Publication Éditeur
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ISSN 0079-6611 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ 51673 collection 2349
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Auteur Faure, V.; Pinazo, C.; Torréton, J.-P.; Douillet, P.
Titre Modelling the spatial and temporal variability of the SW lagoon of New Caledonia II: Realistic 3D simulations compared with in situ data Type Article scientifique
Année 2010 Publication Revue Abrégée Marine Pollution Bulletin
Volume 61 Numéro 7–12 Pages 480-502
Mots-Clés Biogeochemistry; Coupled models; New Caledonia; Physics; lagoon
Résumé Coral reef lagoons are under the growing influence of anthropogenic activities, leading to increasing loads of nutrients and various contaminants. Modelling approaches are a useful tool for studying such a complex coastal environment. In this study, we carried out the development of a three-dimensional coupled hydrodynamical-biogeochemical model of the south-west lagoon of New Caledonia. The biogeochemical model presented in Faure et al. (2006, 2010) was dynamically coupled with a hydrodynamical model (MARS3D) in order to study the short-term variability of the ecosystem. Two simulations (in winter and summer) were then performed from measured initial conditions using realistic wind and irradiance conditions and river inputs. Examinations of the biogeochemical response to these transient meteorological conditions were presented and compared with temporal field data corresponding to the considered periods. Results highlighted the ecosystem functioning, based on the balance of hydrodynamical and biogeochemical processes. Influence of urban and terrigeneous inputs were limited to the coastal zone. The model accurately reproduced the measured Chl.a and bacterial production, highlighting the improvement made on the biogeochemical model. However, the underestimation of some variables in model outputs, in particular nutrients, led us to focus on different inputs, such as sediment inputs which were not taken into account or properly estimated. Moreover, the role of boundary waters appeared crucial and suggested a calibration effort. Last, the final aim of our modelling study will help the development of a useful tool for studying the key processes of the ecosystem of the south-west lagoon of New Caledonia, as well as the examination of the biogeochemical response under different scenarios.
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ISSN 0025-326x ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 721
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Auteur Halo, I.; Backeberg, B.; Brito, A.; Collins, C.; Cossa, O.; Gemo, F.; Jose, Y.; Loveday, B.; Malauene, B.; Marsac, F.; Maueua, C.; Maury, O.; Mavume, A.; Nehama, F.; Penven, P.; Pous, S.; Reason, C.; Roberts, M.; Shillington, F.
Titre JEAI-MOCAs : a multi-institutional initiative to build marine research capacity in Mozambique Type Article scientifique
Année 2013 Publication Revue Abrégée South African Journal of Science
Volume 109 Numéro 7-8 Pages
Mots-Clés biogeochemistry; ocean eddies; ocean models; tides; tropical cyclones
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ISSN 0038-2353 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1470
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Auteur Pagès, R.; Baklouti, M.; Barrier, N.; Richon, C.; Dutay, J.-C.; Moutin, T.
Titre Changes in rivers inputs during the last decades significantly impacted the biogeochemistry of the eastern Mediterranean basin: a modelling study Type Article scientifique
Année 2019 Publication Revue Abrégée Progress in Oceanography
Volume Numéro Pages 102242
Mots-Clés Biogeochemistry; Coupled physical-biogeochemical model; Flexible stoichiometry model; Mediterranean Sea; Nutrient; River inputs
Résumé The Mediterranean Sea (MS) is a semi-enclosed sea characterized by a zonal west-east gradient of oligotrophy, where microbial growth is controlled by phosphate availability in most situations. External inputs of nutrients including Gibraltar inputs, river inputs and atmospheric deposition are therefore of major importance for the biogeochemistry of the MS. This has long been considered to be driven mainly by nutrient exchanges at Gibraltar. However, recent studies indicate that river inputs significantly affect nutrients concentrations in the Mediterranean Sea, although their resulting impact on its biogeochemistry remains poorly understood. In this study, our aim was to make good this lack by addressing the large-scale and long-term impact of variations in river inputs on the biogeochemistry of the Mediterranean Sea over the last decades, using a coupled physical-biogeochemical 3D model (NEMO-MED12/Eco3M-Med). As a first result, it has been shown by the model that the strong diminution (60 %) of phosphate (PO4) in river inputs into the Mediterranean Sea since the end of the 1980s induced a significant lowering of PO4 availability in the sub-surface layer of the Eastern Mediterranean Basin (EMB). One of the main consequences of PO4 diminution is the rise, never previously documented, of dissolved organic carbon (DOC) concentrations in the surface layer (by 20% on average over the EMB). Another main result concerns the gradual deepening of the top of the phosphacline during the period studied, thus generating a shift between the top of the nitracline and the top of the phosphacline in the EMB. This shift has already been observed in situ and documented in literature, but we propose here a new explanation for its occurrence in the EMB. The last main result is the evidence of the decline in abundance and the reduction of size of copepods calculated by the model over the years 1985-2010, that could partially explain the reduction in size of anchovy and sardine recently recorded in the MS. In this study, it is shown for the first time that the variations in river inputs that occurred in the last decades may have significantly altered the biogeochemical cycles of two key elements (P and C), in particular in the EMB. To conclude, the magnitude of the biogeochemical changes induced by river inputs and runoff alone over the last thirty years clearly calls for the use of realistic scenarios of river inputs along with climate scenarios for coupled physical-biogeochemical forecasts in the MS.
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ISSN 0079-6611 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2678
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