Dr Terry Done, of AIMS and the Cooperative Research Centre for Ecologically Sustainable Development of the Great Barrier Reef, says... 'the ability of reef plants and animals to make the limestone skeletons that build reefs may be reduced by rising atmospheric carbon dioxide concentrations, which increases the acidity of surface ocean water. In the long term, it may interfere with skeleton growth by reef builders, which could pose a serious threat to the sustainability of reefs worldwide. Reefs may be less able to keep up with rising sea level, and they may be more vulnerable to cyclones, which are also predicted to increase in some areas'.

'This report represents a breakthrough in terms of recognising a previously unidentified global effect on an ocean ecosystem caused by human induced changes in atmospheric chemistry,' says Dr Barrie Pittock, of CSIRO's Division of Atmospheric Research. 'The recent Kyoto agreement on a reduction in CO₂ emissions will by itself have little effect on the magnitude of this effect over the coming century.'

According to the group's report, local damage can be isolated and managed provided that the surrounding marine ecosystem remains stable. Science's understanding of natural renewal, adaptation, and the critically important limestone creation mechanisms are all inadequate to predict detailed, local effects of the added pressure caused by increasing CO₂ emissions. However the report was confident that more atmospheric CO₂ makes reefs even more vulnerable to natural disturbances, and to stresses resulting from human population growth and development.

Dr Bradley Opdyke of ANU said 'We need to take seriously the possibility that the combination of pressures may push reef communities across some critical survival threshold. This is important to anticipate, because we can't fix it after a crash. We can re-plant some terrestrial forests and grasses, but big marine ecosystems have to rely on their own resources to regenerate and repair themselves'.

Done remarked 'The coral reef managers in Australia such as the Great Barrier Reef Marine Park Authority and Western Australia's Department of Conservation and Land Management are way out in front of the rest of the world in management philosophy and implementation. They have their hands full addressing local pollution, run-off, fishing levels, tourism, shipping and other direct human use of reefs. However, up till now they have been able to assume global climate change would be neutral or even advantageous to our coral reefs. Our report suggests that governments, managers and scientists will need to take a hard look at that assumption'.

For further information or a copy of the summary report, contact:

1. Dr Terry Done, Australian Institute of Marine Science, PMB No. 3, Townsville MC Qld 4810, telephone +61 7 4753 4344; facsimile +61 7 4772 5852; e-mail: t.done@aims.gov.au; or
2. Dr Barrie Pittock, CSIRO Division of Atmospheric Research, Private Bag No. 1, Aspendale Vic 3195, telephone +61 3 9239 4527; facsimile +61 3 9239 4444; e-mail: abp@dar.csiro.au

Results are a report of Working Group 104 of the Scientific Committee on Oceanic Research (SCOR), which is co-sponsored by the Land-Ocean Interactions in the Coastal Zone (LOICZ) core project of the International Geosphere-Biosphere Programme (IGBP). Meeting support was provided by the United State's National Oceanographic and Atmospheric Administration's Coastal Ocean Program and the Society for Integrative and Comparative Biology (SICB), with meeting co-sponsorship by the International Society for Reef Studies (ISRS), the Ecological Society of America (ESA) and the New England Aquarium, Boston.

Symposium participants:

Key conclusions were:

• The calcification rates of corals, coralline algae, and coral-algal communities depends on the calcium carbonate saturation state of surface seawater and are expected to be reduced by rising atmospheric carbon dioxide. This represents a global, systemic, climate-related threat to the functioning of reef ecosystems that will interact with the more immediate anthropogenic local stresses.

• Coral reefs and communities are products of processes operating over a wide range of interacting time and space scales, with fundamentally different controls operating at different scales. While short-term responses will be controlled by local environmental conditions and biotic responses, the longer-term sustainability of a reef system depends on the recruitment, dispersal, persistence and interactions of populations at larger scales.

• Corals, and to some extent reef communities, possess numerous mechanisms for acclimatisation and adaptation - diverse reproductive strategies, flexible symbiotic relationships, physiological acclimatization, habitat tolerance, and a range of community interactions. However, current understanding of these mechanisms, as well as of the critically important calcification mechanisms, is inadequate to explain the past success of corals and reefs or to ensure their conservation for the future.