Scientists warn growing acidity of oceans will kill reefs


Extra carbon dioxide in the air, caused by the burning of fossil fuels, is not only spurring climate change, but is making the oceans more acidic - endangering the marine life that helps to remove carbon dioxide from the atmosphere.

So alarmed have marine scientists become about this that special briefings have been held for government departments. Carol Turley, head of science at Plymouth Marine Laboratory, warned of a "potentially gigantic" problem for the world.

"It is very urgent to warn people what is happening," she said. "Many of the species we rely on to eat, like cod, will disappear. In cartoon form, you could say people should prepare to change their tastes and switch from cod and chips to jellyfish and chips. The whole composition of life in the oceans will change."


Although the phenomenon is caused by excess carbon dioxide in the atmosphere, it is not a "global warming" problem, but a simple chemical reaction between air and sea.

Carbon dioxide mixed with water produces carbonic acid which is making the alkaline oceans more acidic. But for hundreds of thousands and probably millions of years plankton, shellfish and corals have adapted to use the stable levels of calcium and carbon in the sea to make their shells.

"Scientists did not look at this problem because everyone assumed the chemical composition of the sea was constant. But this change is 'O-level' chemistry and we missed it," said Dr Turley.

The oceans' vital role in limiting CO2 levels in the air will have to be reassessed in light of the findings.

Plankton are as important as plants and trees in the take-up of carbon. Scientists estimate that about half the 800 billion tonnes of CO2 put into the atmosphere by mankind since the start of the industrial revolution has been soaked up by the sea. Much of the carbon is fixed in the shells of creatures called coccolithphores, the tiny plankton whose bodies make up the white cliffs of Dover. They live on the ocean surface in trillions and when they die their shells sink to the bottom taking the carbon with them. They could not survive in a more acidic sea and their removal of carbon from the atmosphere would stop.

"These creatures are part of our survival bubble. The oceans give us a sustainable atmosphere by taking out the carbon dioxide. They're the lungs of the planet. People have not woken up to the potential impact their removal will cause," said Dr Turley.

The acidity of liquid is measured on the pH scale, from one to 14, with seven being neutral, and the higher the number the more alkaline. The oceans have previously recorded an 8.2 pH reading, but this has now dropped to 8.1 and is continuing to fall.

The sea around Britain has been found to be more acid than many other areas, partly because of ocean currents, but mainly because Europe and North America are the largest carbon dioxide emitters.

Experiments show that even a small increase in acidity reduces the ability of shellfish and plankton to grow and causes a population fall.

The loss of corals would seriously affect small islands and coasts.

The fundamental problem is the effect on the food chain. Zooplankton, essential food for fish, could suffer increasing mortality rates and starfish, whelks and other shellfish, eaten by cod, might perish.

This might lead to population explosions of other creatures, such as jellyfish, or crabs, shrimps and lobsters which rely on chitin rather than calcium for their shells.

The Royal Society has set up a working group to study the problem. Plymouth Marine Laboratory is installing special tanks to aid the research.

The conference on avoiding dangerous climate change was held at the Meteorological Office in Exeter. At its conclusion, the steering committee of senior scientists identified the growing acidity of the oceans as a new impact that was "potentially disturbing". It would reduce the oceans' capacity to remove CO from the atmosphere and affect the entire marine food chain.

Participants at the conference also concluded that the risks from rising temperatures were "more serious than previously thought".