ON AN idyllic coral atoll just a two-hour boat ride from Queensland's Gladstone Harbour, out past the endless line of tankers queued to load coal for export, a half-dozen scientists work frantically against the tide. Their objective? To explore the Impact of climate change on reefs, including the consequences of rising atmospheric carbon - on the delicate chemistry of the reef and the creatures living there.

The project team, led by the University of Queensland's Global Change Institute, is completing tests on a new underwater laboratory that will expose living corals on the Great Barrier Reef to the more acidic conditions forecast for oceans by the end of the century. A Queensland University researcher tests the Barrier Reef laboratory that will expose corals to the more acidic conditions forcase for oceans by the end of the century.

Fathoming the effects of ocean acidification - the ''other'' carbon problem, one that emerged in scientific literature only a decade ago - has become one of the most urgent issues on the science agenda. The potentially diabolical consequences were highlighted in major briefing papers presented last week by the United States National Research Council to the US Congress and by the European Science Foundation to national leaders. The papers appealed to governments to give the issue priority for investigation and action.

The Heron Island experiment assumes a future with seawater twice as acidic as today, a more conservative take than published business-as-usual scenarios, which put the increase at 150 per cent by 2100. The question scientists are racing to answer is what a more acidic environment will mean for the tiny shelled zooplankton on which the marine food chain depends, and for the skeletons corals build into reefs.

The fear is that the change hits these creatures on two fronts - creating a more corrosive environment, and depleting stocks of building materials. ''If these organisms can't compensate for that … reef growth will slow until the reef superstructure begins to crumble.''

Meanwhile, he says, reefs are struggling with the effects of rising temperatures, which can trigger bleaching - when the stressed coral hosts expel the microscopic algae on which they rely for survival.
''Something as complex and broad a feature as coral reefs is now sickening and dying … This is really giving us a warning sign that maybe the whole basis of our dependence on this planet, the biological and ecological services, will change.''

seaweed for thought..