Assessment of the importance of the carbonate pump in surface waters of the Bay of Biscay

Marine carbon research in the past decade has been mainly devoted to the understanding and quantification of processes controlling the fluxes of organic matter in the ocean. Little attention has been paid until now to the particulate inorganic carbon whose net fluxes to the sediments are comparable to those of the organic matter. There remains still a large uncertainty in the production and the fate of biogenic calcium carbonate in the oceanic carbon cycle.

In the framework of the Belgian global change programme, we have developed a project devoted to the study of the inorganic carbon cycle in the Bay of Biscay where coccolithophorid blooms occur frequently. The study focuses on processes associated with the oceanic production and dissolution of calcium carbonate, by combining field investigations, laboratory experiments and modelling efforts. The rate of primary production and of calcification by phytoplankton is evaluated by 14C incubation experiments during a coccolithophorid bloom-forming period in the area of investigation.

The relative production of organic matter and calcium carbonate in the photic zone along a transect from the continental shelf across the slope to deep waters will be presented. A tentative mass balance of the carbon fluxes for this area will be constructed. These preliminary results confirm the importance that the calcium carbonate pump may play in open ocean.