[en] We measured particulate and dissolved organic carbon (POC and DOC), chlorophyll, oxygen, partial pressure of Co-2, pH, total alkalinity (TAlk) and particulate inorganic carbon (PIC) during a late summer cruise in the eutrophic Loire estuary. These parameters reveal an intense mineralisation of organic matter in the estuarine maximum turbidity zone (MTZ) that results in oxygen deficits (down to 20% of the saturation level) and high CO2 oversaturations (pCO(2) up to 2900 muatm). Several facts revealed the occurrence of carbonate dissolution in the Loire MTZ: large amounts of alkalinity were produced in the upper estuary, increasing its transfer to the ocean by 30%; the calculated saturation index showed a net undersaturation for aragonite and a slight undersaturation for calcite in the MTZ; and PIC decreased from 2.1% (% dry weight) in riverine suspension to 0.4% in the MTZ. A stoichiometric approach is used to assess the coupling between aerobic respiration and carbonate dissolution, where apparent oxygen utilisation, excess CO2, TAlk and dissolved inorganic carbon are compared quantitatively. About 20%, of the CO2 generated by respiration was involved in carbonate dissolution. The loss of PIC at the river-estuary transition quantitatively corresponds to the amount of authigenic calcite precipitated upstream in the highly eutrophic river. This suggests that CO2 exchange with the atmosphere along the eutrophic river-estuary continuum is buffered by carbonate precipitation in the autotrophic river and its dissolution in the heterotrophic estuary.
Research Center/Unit :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Abril, Gwenaël; Université Bordeaux 1 > Département de Géologie et Océanographie
Etcheber, Henri; Université Bordeaux 1 > Département de Géologie et Océanographie
Delille, Bruno ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Océanographie chimique
Frankignoulle, Michel; Université de Liège - ULiège > Institut de Physique > Unité d’Océanographie Chimique
Borges, Alberto ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Océanographie chimique
Language :
English
Title :
Carbonate dissolution in the turbid and eutrophic Loire estuary
Publication date :
2003
Journal title :
Marine Ecology. Progress Series
ISSN :
0171-8630
eISSN :
1616-1599
Publisher :
Inter-Research, Oldendorf Luhe, Germany
Volume :
259
Issue :
-
Pages :
129-138
Peer reviewed :
Peer Reviewed verified by ORBi
Name of the research project :
Biogest
Funders :
DG RDT - Commission Européenne. Direction Générale de la Recherche et de l'Innovation F.R.S.-FNRS - Fonds de la Recherche Scientifique
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