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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, C09S06, doi:10.1029/2004JC002528, 2005

Low coral cover in a high-CO₂ world

Ove Hoegh-Guldberg

Centre for Marine Studies, University of Queensland, St. Lucia, Queensland, Australia

Abstract

Coral reefs generally exist within a relatively narrow band of temperatures, light, and seawater aragonite saturation states. The growth of coral reefs is minimal or nonexistent outside this envelope. Climate change, through its effect on ocean temperature, has already had an impact on the world's coral reefs, with almost 30% of corals having disappeared since the beginning of the 1980s. Abnormally warm temperatures cause corals to bleach (lose their brown dinoflagellate symbionts) and, if elevated for long enough, to die. Increasing atmospheric CO₂ is also potentially affecting coral reefs by lowering the aragonite saturation state of seawater, making carbonate ions less available for calcification. The synergistic interaction of elevated temperature and CO₂ is likely to produce major changes to coral reefs over the next few decades and centuries. Known tolerances of corals to projected changes to sea temperatures indicate that corals are unlikely to remain abundant on reefs and could be rare by the middle of this century if the atmospheric CO₂ concentration doubles or triples. The combination of changes to sea temperature and carbonate ion availability could trigger large-scale changes in the biodiversity and function of coral reefs. The ramifications of these changes for the hundred of millions of coral reef–dependent people and industries living in a high-CO₂ world have yet to be properly defined. The weight of evidence suggests, however, that projected changes will cause major shifts in the prospects for industries and societies that depend on having healthy coral reefs along their coastlines.

Received 12 June 2004; accepted 28 December 2004; published 24 August 2005.

Keywords: climate change; corals; dinoflagellate symbionts; coral bleaching; aragonite saturation state.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions (0426, 1610); 1635 Global Change: Oceans (1616, 3305, 4215, 4513); 4805 Oceanography: Biological and Chemical: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912); 4815 Oceanography: Biological and Chemical: Ecosystems, structure, dynamics, and modeling (0439); 4825 Oceanography: Biological and Chemical: Geochemistry.

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Citation: Hoegh-Guldberg, O. (2005), Low coral cover in a high-CO₂ world, J. Geophys. Res., 110, C09S06, doi:10.1029/2004JC002528.

Copyright 2005 by the American Geophysical Union.