National Research Council Study Finds CO2 Emissions Causing Ocean Acidification at Unprecedented Rate

The chemistry of the ocean is changing at an unprecedented rate and
magnitude due to anthropogenic carbon dioxide emissions; the rate of change exceeds any known to have occurred for at least for at least 800,000 years, concludes a congressionally requested study by the US National Research Council.

Unless anthropogenic CO₂ emissions are substantially curbed, or atmospheric CO₂ is controlled by some other means, the report finds, the average pH of the ocean will continue to fall. Ocean acidification has demonstrated impacts on many marine organisms. While the ultimate consequences are still unknown, there is a risk of ecosystem changes that threaten coral reefs, fisheries, protected species, and other natural resources of value to society.

The ocean absorbs a significant portion of carbon dioxide (CO₂) emissions from human activities, equivalent to about one-third of the total emissions for the past 200 years from fossil fuel combustion, cement production and land use change, the report notes. While the uptake of CO₂ by the ocean benefits society by moderating the rate of climate change, it also causes unprecedented changes to ocean chemistry, decreasing the pH of the water and leading to a suite of chemical changes collectively known as ocean acidification.

It is important to note that the concentration of atmospheric CO₂ is rising too rapidly for natural, CaCO₃-cycle processes to maintain the pH of the ocean. As a consequence, the average pH of the ocean will continue to decrease as the surface ocean absorbs more atmospheric CO₂.

—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 unit drop by the end of the century.

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. 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 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; and
• 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 US Geological Survey, and the National Science Foundation. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies.

These are independent, nonprofit institutions that provide science, technology, and health policy advice under an 1863 congressional charter