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Balance of organic fluxes in the Gironde dilution plume : ecological importance of microbial loop and microbial food web processes in spring, in the photic zone

Océanographie du Golfe de Gasgogne (Biarritz, 4-6 avril 2000)

Auteur(s) et Affiliation(s)

ARTIGAS, Luis Felipe
Université du Littoral Côte d'Opale, maison de la recherche en environnement naturel, UPRES-A 8013 Elico, 32 avenue Foch, 62930 Wimereux, France
LABORDE, Pierre
Université de Bordeaux 1, laboratoire d'océanographie biologique, UMR-CNRS-EPOC 5805, 2 rue du Pr Jolyet, 33120 Arcachon, France
SAUTOUR, Benoit
Université de Bordeaux 1, laboratoire d'océanographie biologique, UMR-CNRS-EPOC 5805, 2 rue du Pr Jolyet, 33120 Arcachon, France
DELMAS, Daniel
Crema L'Houmeau, BP 5, 17137 L'Houmeau, France
HERBLAND, Alain
Crema L'Houmeau, BP 5, 17137 L'Houmeau, France


Description :
Characteristics of the pelagic ecosystem of the French bay of Biscay submitted to the influence of the Gironde dilution plume were defined, in spring, taking into account the structure and magnitude of both microplanktonic stocks and dynamics, the importance of trophic transfers, and the magnitude of carbon downward fluxes. Notwhithstanding the differences in both biomass and production rates measured during the three different spring periods, nano- and picoplanktonic cells were predominant, and autotrophy appeared to be limited by the phosphate concentration during the whole period. The bacterial heterotrophic production represented, as a mean, from 10% to 33% of the autotrophic production according to the period considered. On the other hand, the herbivorous grazing on microautotrophs was responsible for the loss of 15% to 100% of the daily primary production, whereas an average of 45% of the net daily bacterial production was consumed by bacterivores in spring. Finally, very low sedimentation rates were measured at the base of the euphotic zone in the three spring periods. The inner-shelf euphotic zone constituted, in spring, a maintenance system where microbial loop and microbial food web processes, in addition to playing an important role in sustaining the regenerated primary production, seemed to act as a potential microbial barrier to the organic matter sedimentation (intense bacterial hydrolysis measured in sinking aggregates).


Type de document :
Congrès

Source :
Colloque international d'océanographie du Golfe de Gascogne, 7, Biarritz, France, 2000-04-04, Actes de colloques - IFREMER, issn : 0761-3962, 2001, vol. 31, p. 126-136, Références bibliographiques : 2 p.3/4

Date :
2001

Identifiants :
isbn : 2-84433-054-1

Editeur :
Pays édition : France, Plouzané, Institut français de recherche pour l'exploitation de la mer

Langue :
Anglais
Droits :
Tous droits réservés © Prodig - Bibliographie Géographique Internationale (BGI)