Coral reefs cover 617000 km2 and are then a major ecosystem of the shallow ocean. In terms of carbon cycle, reefs are sites of two important processes: the organic carbon metabolism (photosynthesis & respiration) and the inorganic carbon metabolism (calcification & dissolution of calcium carbonate).
The Chemical Oceanography Unit, from the University of Liège, works on inorganic carbon dynamics in coral reefs, with a special attention to the metabolism effects on air-sea CO2 exchanges. Our approach is experimental and theoretical:
Six field works have been carried out since 1991:
We have shown that coral reefs behave as global source of atmospheric CO2, due to the relative importance of calcification process which, contrary to photosynthesis, induces a release of dissolved CO2 in the surrounding water. The results obtained from field works have also shown that measured fluxes highly depend on studied site, the season and the health state of the ecosystem.
The chemical equation that describe calcification clearly shows that for each mole of carbonate precipitated, one mole of dissolved CO2 is released in the surrounding water. The so-released CO2 will then react with other bases (mainly carbonate and borate in seawater) to reach the equilibrium state. The effective increase of dissolved CO2 depends on the buffering capacity and we have developed equations that allow to compute these processes in seawater. Calculations have shown that the amount of CO2 that must be released to equilibrate seawater increases with increasing partial pressure of CO2 in seawater. Calcification then presents a positive feedback to the human induced atmospheric CO2 increase.International Collaborations
This research project is carried out in collaboration with:
Gattuso J.-P., Reynaud-Vaganay, S, Furla, P., Romaine-Lioud, S., Jaubert, J., Bourge, I. and Frankignoulle M. (2000) Calcification does not stimulate photosynthesis in the zooxanthellate scleractinian coral Stylophora pistillata. Limnology and Oceanography, 45(1), 246-250.
Gattuso J.-P., Frankignoulle M. and Smith S.V. (1999) Measurement of community metabolism and significance of coral reefs in the CO2 source-sink debate. Proceedings of the National Academy of Science, USA, 96(23), 13017-13022.
Gattuso J.-P., Allemand, D. and Frankignoulle M. (1999) Interactions between the carbon and carbonate cycles at organism and community levels in coral reefs; a review on processes, rates and environmental control. American Zoologist, 39(1), 160-183.
Gattuso J.-P., M. Frankignoulle and Wollast R. (1998) Carbon and carbonate metabolism in coastal aquatic ecosystems. Annual Review of Ecology and Systematics, 29:405-433, doi:10.1146/annurev.ecolsys.29.1.405
Gattuso J.-P., Frankignoulle, M., Bourge, I., Romaine, S. and Buddemeier B. (1998) Effect of calcium carbonate saturation of seawater on coral calcification. Global and Planetary Change, 18(1-2): 37-46, doi:10.1016/S0921-8181(98)00035-6
Gattuso J.-P., Payri, C. E., Pichon, M., Delesalle, B. and Frankignoulle M. (1997) Primary production, calcification and air-sea CO2 fluxes of an algal-dominated coral reef community (Moorea, French Polynesia). Journal of Phycology 33:729-738.
Frankignoulle M. , Gattuso J. - P., Biondo R. , Bourge I., Copin-Montégut G. and M. Pichon M. (1996) Carbon fluxes in coral reefs. II. Eulerian study of inorganic carbon dynamics and measurement of air-sea CO2 exchanges. Marine Ecology Progress Series, 145, 123-132.
Gattuso J.-P., Canon, C., Delesalle, B., Pichon, M. and Frankignoulle M. (1996) Carbon fluxes in coral reefs. I. Lagrangian measurement of community metabolism and resulting air-sea CO2 desequilibrium. Marine Ecology Progress Series, 145, 109-121.
Gattuso J.-P., Frankignoulle M., Smith S. V., Ware J. and Wollast R. (1996) Coral reefs and carbon dioxide. Science, 271, 1298.
Frankignoulle M., Pichon M. and Gattuso J.P. (1995) Aquatic calcification as a source of carbon dioxide. In Proceedings of the NATO ARW on Carbon Sequestration in the Biosphere, Beran A. (ed), Elsevier, 133 , 265-271.
Gattuso J.-P., Pichon, M. and Frankignoulle M. (1995) Atmospheric CO2, marine production and calcification. Marine Ecology Progress Series, 129, 307-312.
Frankignoulle M. (1994) A complete set of buffer factors for acid/base CO2 system in seawater. Journal of Marine Systems, 5, 111-118, doi:10.1016/0924-7963(94)90026-4
Frankignoulle M., Canon C. and Gattuso J.-P. (1994) Marine calcification as a source of carbon dioxide: positive feedback of increasing atmospheric CO2. Limnology and Oceanography, 39, 458-462.
Delesalle B., Pichon, M., Frankignoulle M. and Gattuso J.P. (1993) Effects of a cyclone on coral reef phytplankton biomass, primary production and composition (Moorea Island, French Polynesia). Journal of Plankton Research, 15, 1413-1423.
Frankignoulle M. and Gattuso J.-P. (1993) Air-sea CO2 exchanges in coastal ecosystems. In Interactions of the C, N, P, S biogeochemical cycles and Global Change, Wollast R., Mackenzie F.T. & L. Chou (eds). NATO ASI Series 14: 233-248. Springer-Verlag Berlin.
Gattuso J.-P., Pichon, M., Delesalle, B. and Frankignoulle M. (1993) Community metabolism and air-sea CO2 fluxes in a coral reef ecosystem (Moorea, French Polynesia). Marine Ecology Progress Series, 96, 259-267.