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Overkoepelend project: Research action SPSD-II: Second scientific support plan for a sustainable development policy, meer
Referentie nr.: EV/05
Periode: December 2000 tot Februari 2005
Thesaurustermen: Air-sea exchanges; Calciumcarbonaten; Dissolved gases; Klimaat; Koolstofdioxide
Geografische term: ANE, Biscay Bay [gazetteer]
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- LoCGE: Université Libre de Bruxelles; Faculté des Sciences; Département des Sciences de la Terre et de l'Environnement; Unité Modélisation Biogéochimique Système Terre; Laboratory of Chemical Oceanography and Water Geochemistry, meer
- ECOL: Vrije Universiteit Brussel; Faculteit Wetenschappen; Vakgroep Biologie; Laboratorium voor Ecologie en Systematiek, meer, partner
- MITAC: Universiteit Antwerpen; Faculteit Wetenschappen; Departement Scheikunde; Onderzoeksgroep Micro- en Sporenanalyse, meer, partner
- BELSPO: Federaal Wetenschapsbeleid, meer, financier
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The ocean constitutes a large sink for anthropogenic CO2 and thus plays a significant role in the global biogeochemical cycle of carbon and its perturbations. There remain, however, large uncertainties concerning the uptake of anthropogenic carbon by the ocean, mainly due to insufficient knowledge of processes controlling the pCO2 in surface waters.
Most of the previous research efforts have been concentrated on the study of CO2 exchange at the air-sea interface due to temperature effects related to the general circulation of water masses or to the biological activity in terms of new production of organic matter and export to deep waters. The effect of precipitation of calcium carbonate by calcifying organisms in the euphotic zone and the redissolution of their skeletons has presently not been fully taken into account. The precipitation and dissolution processes affect both dissolved inorganic carbon concentration and alkalinity, and plays thus a significant role in the buffering capacity of seawater and its potential to act as a sink or a source of CO2 for the atmosphere. It becomes now evident that one source of the uncertainties for the flux of anthropogenic carbon is related to our poor knowledge of these processes and their quantification, which are fundamental not only for the understanding of the present-day situation but also for the predictive studies in the context of global warming.
The overall objective of this research project is to gain a better knowledge of the oceanic inorganic carbon cycle and its role in climate change. With the combination of field investigations, laboratory experiments and modelling efforts, we aim to study the processes associated with the oceanic production and dissolution of calcium carbonate in order to quantify the role of calcifying phytoplanktonic organisms in sequestering CO2.
Our field studies will be carried out in the area of La Chapelle Bank area (about 47°30'N, 7°30'W) in the Gulf of Biscay. This site has been regularly visited since more than one decade in the framework of Belgian (Global Change) or European (OMEX) research projects, and can be considered as a "time-series" station for which a database of fundamental parameter exist and a good knowledge of the physical processes occurring there has been obtained. In addition, frequent coccolithophore blooms have been observed in the Gulf of Biscay and our measurements of the vertical distribution and fluxes of calcium carbonate indicate a rapid dissolution of the skeletons during settling even in the upper water column over-saturated with respect to CaCO3. This site is thus a suitable location for studying the oceanic inorganic carbon cycle.
Field investigations, supported by remote sensing data, will provide basic, physical, chemical (nutrients, carbon organic and inorganic species), biological (phytoplankton and zooplankton) information. Suspended matter will be collected by continuous centrifugation, in situ filtration of large volumes of water and short-term deployments of sediment traps. In addition, process-oriented studies of the production of organic and inorganic particulate carbon and the dissolution of calcium carbonate will be conducted, using 14C incorporation experiments. The influence of zooplankton grazing and of microbial degradation of organic matter on the dissolution of CaCO3 will be investigated in detail.
Particulate material collected in the Gulf of Biscay will be studied from a physical and chemical point of view using modern microscopic and spectroscopic methods. Different electron microbeam techniques will be used for the characterisation of individual biotic and abiotic suspended particles for their composition, morphology and dissolution features. The calcite surface will be examined by backscattered electrons and by a microprofiler to detect such features, and by "variable-eneragy" electron microprobe analysis to obtain information on the residual organic layer. Particles will also b