(UNEP Press Release) Acidification may push already over-stressed oceans into the red

Cancun/Nairobi/Plymouth, 2 December 2010 – The future impact of rising emissions on the health of seas and oceans may be far more wide-ranging and complex than was previously supposed, a new report released at the UN climate convention meeting in Mexico says.

The study, entitled the Environmental Consequences of Ocean Acidification, has brought together some of the latest scientific research on ‘ocean acidification’, a process triggered by increasing concentrations of dissolved C02 which is changing the sea’s chemistry by lowering the pH of the marine environment.

Launched by the United Nations Environment Programme (UNEP), the report confirms concerns that some organisms, such as corals and shellfish may find it increasingly difficult to form their skeletons in the decades to come making it harder to survive let alone thrive. It also shows that ocean acidification can react together with ocean warming so that animals such as crabs have a reduced range of temperatures they can thrive in.

This in turn may have significant future impacts on catches of crabs, mussels and other shellfish; species dependent on coral reefs and ones such as salmon that feed on smaller, shell-building organisms lower down the food chain known as ptetropods, for example.

Other new research is spotlighting fresh areas of concern including findings that some species, including the clown fish made famous in the Disney cartoon Finding Nemo, may find it harder to avoid their predators and to find their way home.

If other fish react the same way, this may have implications for the marine food chain upon which billions of people depend directly or indirectly for protein and livelihoods.

Achim Steiner, UN Under-Secretary General and UNEP Executive Director, said: “Ocean acidification is yet another red flag being raised, carrying planetary health warnings about the uncontrolled growth in greenhouse gas emissions. It is a new and emerging piece in the scientific jigsaw puzzle, but one that is triggering rising concern”. ‘Whether ocean acidification on its own proves to be a major or a minor challenge to the marine environment and its food chain is to date unknown. But the phenomenon comes against a backdrop of already stressed seas and oceans as a result of over-fishing to other forms of environmental degradation. Thus the public might quite rightly ask how many red flags do governments need to see before the message to act gets through,” he said.

The report was compiled in collaboration with the Plymouth Marine Laboratory in the United Kingdom and scientists from other organisations including the National Oceanography Centre in Southampton and the Intergovernmental Oceanographic Commission of UNESCO.

Carol Turley, a senior scientist at the laboratory; Knowledge Exchange Coordinator for the UK Ocean Acidification Research Programme, and lead author of the new report, said: “As scientists around the world start to investigate the potential impacts of ocean acidification, we are seeing an overall negative impact from ocean acidification directly on organisms and on some key ecosystems that help provide food for billions. We need to start thinking about the risk to food security.”

Dr. Turley stressed that researchers were working on the frontiers of science in respect to ocean acidification and its potentially complex impact on the marine environment and its organisms.

She added that some research indicated that adult lobsters, for example, might actually increase shell-building in response to falling pH levels whereas it may be the juveniles who are less able to build healthy skeletons.

A similar possibility may arise in respect to adult and juvenile forms of fish with the olfactory or smelling systems of some species of young fish impaired but adults unaffected.

Meanwhile, there is some evidence of other curious changes if emissions continue to rise and concentrations of C02 continue to build-up in the seas and oceans. For example, brittle stars, an important part of the marine food chain, may increase shell-building at the cost of muscle formation, some science suggests.

“It is clearly not enough to look at a species. Scientists will need to study all parts of the life-cycle to see whether certain forms are more or less vulnerable. Meanwhile, the ability, or inability, to build calcium-based skeletons may not be the only impact of acidification on the health and viability of an organism: brittle stars perhaps being a case in point,” said Dr. Turley.

The report points out that there may be “winners” as well as “losers”, with photosynthetic organisms such as seagrasses likely to benefit from rising acidification. Yet studies of natural C02 vents in the Mediterranean Sea show that although there are some “winners” the ecosystem is likely to be altered in other ways.

The report calls on governments, policymakers and others to consider a range of actions including:

  • Rapid and substantial cuts to man-made CO2 emissions to the atmosphere in order to reduce ocean acidification;
  • Determine the vulnerability to ocean acidification of human communities dependent on marine resources;
  • Identify species that are more flexible to change and assess how these may affect ecosystems and food security;
  • Reduce other pressures on food fish stocks to provide the best chance of success through, for example, marine spatial planning or re-evaluating available resources and their usage;
  • Assess the options for the development of environmentally sustainable ‘aquaculture’ options using species that may be more resistant to lowered pH;
  • Embrace the science of ocean acidification into fisheries management tools.

Key Findings from the Report

Around 25 per cent of the world’s C02 emissions are being absorbed into the seas and oceans where it converts to carbonic acid.

This is lowering the pH of the oceans and affecting its chemistry. For example, the concentrations of carbonate ions is decreasing and is linked to the ability of many marine organisms to build reefs and shells.

  • The report says that the chemistry of the oceans is being altered at a speed not seen for 65 million years since the extinction of the dinosaurs;
  • The mean pH of the marine world has decreased by 30 per cent and the concentration of carbonate ions has fallen by 16 per cent since the industrial revolution;
  • Based on current rates of CO2 emissions, projections show that by the end of the 21st century, global ocean pH will decrease by a further 0.3 units, which represents a total increase in acidity of 150 per cent.

    Fish including shellfish contribute 15 per cent of animal protein for three billion people worldwide, and a further one billion people rely on fisheries for their primary source of protein.

  • The report says that many marine organisms have ways of compensating for changes in seawater chemistry, although they may have to spend more energy doing this in an increasingly more acidic ocean;
  • However, studies of mussels and sea urchin species have shown that they have only a partial or no compensation mechanism, potentially making them more vulnerable.

    Around 80 per cent of fish catches occur in just 10 per cent of the oceans, including key areas such as Continental shelves and estuaries.

  • The report says that “many of these areas are also projected to be very vulnerable to ocean acidification this century”;
  • The aquaculture industry is the fastest growing food producer worldwide, increasing at a rate of 7 per cent per annum and the proportion of fish produced by aquaculture and consumed by humans worldwide has risen to 50 per cent of total production.

  • The report says that these industries are now at risk from future ocean acidification both directly through the impact on the organisms themselves and indirectly through the food webs and habitats they depend on.

    Tropical reefs provide shelter and food for an estimated 25 per cent of known marine fish species, and account for between 9 and 12 per cent of world fish landings.

    Consequently, these coral reefs provide food and livelihood security for some 500 million people worldwide.

  • The report says it is anticipated that future ocean acidification is likely to affect adult and juvenile coral growth and recruitment, coralline red algae growth, reef structural integrity and potentially even the density of bio-eroding grazers and predators.

    Environmental Consequences of Ocean Acidification:A Threat to Food Security is available at

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