Horizon / Plein textes La base de ressources documentaires de l'IRD

IRD

 

Publications des scientifiques de l'IRD

Machu Eric, Capet X., Estrade P. A., Ndoye S., Brajard J., Baurand François, Auger P. A., Lazar A., Brehmer Patrice. (2019). First evidence of anoxia and nitrogen loss in the Southern Canary Upwelling System. Geophysical Research Letters, 46 (5), 2619-2627. ISSN 0094-8276

Accès réservé (Intranet IRD) Demander le PDF

Lien direct chez l'éditeur doi:10.1029/2018gl079622

Titre
First evidence of anoxia and nitrogen loss in the Southern Canary Upwelling System
Année de publication2019
Type de documentArticle référencé dans le Web of Science WOS:000462612900032
AuteursMachu Eric, Capet X., Estrade P. A., Ndoye S., Brajard J., Baurand François, Auger P. A., Lazar A., Brehmer Patrice.
SourceGeophysical Research Letters, 2019, 46 (5), p. 2619-2627. ISSN 0094-8276
RésuméThe northeastern Atlantic hosts the most ventilated subsurface waters of any eastern boundary upwelling system, while coastal upwelling source waters are slightly above hypoxic levels. Anoxic conditions have previously been found offshore inside mesoscale eddies whose core waters undergo oxygen consumption for many months. Based on circumstantial in situ observations, this study demonstrates that the Senegalese coastal ocean is subjected to episodic occurrence of zero dissolved oxygen concentration at depth along with elevated nitrite concentration (11mmol/m(3)) and nitrate/nitrite deficit to phosphate, thereby indicating severe anoxia and intense nitrogen loss. The anoxic event was associated with a prolonged upwelling relaxation episode in March 2012 and a nearshore diatom bloom that underwent degradation while being advected offshore in stratified waters. This is consistent with scenarios observed in other upwelling systems (Benguela and California), and such conditions are presumably frequent in the southern part of the Canary system. Plain language summary Oxygen is a key requirement for respiration by marine living organisms. Warming of the atmosphere and the ocean surface reduces the oxygenation of offshore waters. Similarly, the extra load of nutrients from agriculture or waste waters modifies algal production, particularly in coastal regions, often resulting in oxygen-depleted waters. Specific reactions affecting the ionic forms of nitrogen also occur within oxygen-depleted waters, which also impact the nitrogen cycle by generating nitrite, which is poisonous for marine organisms, and nitrous oxide, a powerful greenhouse gas. We took measurements at sea to show that a poorly studied coastal sector of the North Atlantic Ocean, the Senegalese continental shelf, can be episodically subjected to complete depletion of subsurface oxygen (anoxia) as well as high nitrite concentrations, constituting the first report of anoxia for this oceanic region. We also show that this anoxia is likely the consequence of the decay of a bloom of diatoms, a group of microalgae common in this type of ecosystem that initially developed in shallow waters and transported offshore by anomalous currents associated with low-wind conditions.
Plan de classementLimnologie physique / Océanographie physique [032] ; Ecologie, systèmes aquatiques [036]
Descr. géo.ATLANTIQUE NORD ; SENEGAL ; ZONE TROPICALE
LocalisationFonds IRD [F B010075523]
Identifiant IRDfdi:010075523
Lien permanenthttp://www.documentation.ird.fr/hor/fdi:010075523

Export des données

Disponibilité des documents

Télechargment fichier PDF téléchargeable

Lien sur le Web lien chez l'éditeur

Accès réservé en accès réservé

HAL en libre accès sur HAL


Accès aux documents originaux :

Le FDI est labellisé CollEx

Accès direct

Bureau du chercheur

Site de la documentation

Espace intranet IST (accès réservé)

Suivi des publications IRD (accès réservé)

Mentions légales

Services Horizon

Poser une question

Consulter l'aide en ligne

Déposer une publication (accès réservé)

S'abonner au flux RSS

Voir les tableaux chronologiques et thématiques

Centres de documentation

Bondy

Montpellier (centre IRD)

Montpellier (MSE)

Cayenne

Nouméa

Papeete

Abidjan

Dakar

Niamey

Ouagadougou

Tunis

La Paz

Quito