Carbon dioxide emissions causing ocean acidification to progress at unprecedented rate

The ocean absorbs approximately a third of man-made CO₂ emissions, including those from fossil-fuel use, cement production, and deforestation, the summary says. The CO₂ taken up by the ocean decreases the pH of the water and leads to a combination of chemical changes collectively known as ocean acidification.

Since the beginning of the industrial revolution, the average pH of ocean surface waters has decreased approximately 0.1 unit -- from about 8.2 to 8.1 -- making them more acidic. Models project an additional 0.2 to 0.3 drop by the end of the century. This rate of change exceeds any known to have occurred in hundreds of thousands of years, the report says. The ocean will become more acidic on average as surface waters continue to absorb atmospheric CO₂, the committee said.

Studies on a number of marine organisms have shown that lowering seawater pH with CO₂ affects biological processes, such as photosynthesis, nutrient acquisition, growth, reproduction, and individual survival depending upon the amount of acidification and the species tested, the committee found. For example, some of the strongest evidence of the potential effects of ocean acidification on marine ecosystems comes from experiments on organisms with calcium carbonate shells and skeletons. The results showed decreases in shell and skeletal growth in a range of marine organisms, including reef-building corals, commercially important mollusks such as oysters and mussels, and several types of plankton at the base of marine food webs.

The ability of various marine organisms to acclimate or adapt to ocean acidification is unknown, but existing data suggest that there will be ecological winners and losers, leading to shifts in the composition and functioning of many marine ecosystems, the committee said. Such ecosystem changes could threaten coral reefs, fisheries, protected species, and other natural resources.

Although changes in ocean chemistry caused by increasing atmospheric CO₂ can be determined, not enough information exists to assess the social or economic effects of ocean acidification, much less develop plans to mitigate or adapt to them, the committee noted.

The federal government has taken initial steps to respond to the nation's long-term needs with the development of the National Ocean Acidification Program. The committee found that legislation has laid the foundation for a program that will advance our understanding and improve our response to ocean acidification.

The committee recommended six key elements of a successful National Ocean Acidification Program:

• an integrated ocean acidification observation network that includes the development of new tools, methods, and techniques to improve measurements
• research in eight broad areas to fulfill critical information gaps
• assessments to identify stakeholder concerns and a process to provide relevant information for decision support
• a data management office that would ensure data quality, access, and archiving, plus an information exchange that would provide research results, syntheses, and assessments to managers, policymakers, and the general public
• facilities to support high-quality research and training of ocean acidification researchers
• an effective 10-year strategic plan for the program that will identify key goals, set priorities, and allow for community input, in addition to a detailed implementation plan

The study is funded by the National Oceanic and Atmospheric Administration, NASA, the U.S. Geological Survey, and the National Science Foundation.

Ocean Acidification: A National Strategy to Meet the Challenges of a Changing Ocean