New York Climate Rescue

Research Shows Oceans Becoming Acidic As Large Amounts of Carbon Absorbed

PARIS--The world's oceans are absorbing unprecedented amounts of carbon dioxide, increasing water acidity and potentially threatening the survival of many marine species, including corals, shellfish, and phytoplankton, according to a report published July 16 by the United Nations Educational, Scientific, and Cultural Organization.

The research, first unveiled during a mid-May symposium organized by UNESCO's Intergovernmental Oceanographic Commission and the International Council for Science, suggests that rising CO₂ absorption rates in the world's oceans could disrupt marine food chains and alter oceanic biogeochemistry in ways that are not yet understood.

Scientists participating in the UNESCO symposium took no specific position on controversial plans to use the oceans to sequester excess atmospheric CO₂, the most common greenhouse gas.

Instead, they discussed how existing levels of CO₂ absorption are affecting oceans, and ways in which marine biodiversity might be affected by still higher levels of atmospheric carbon dioxide.

120 Billion Metric Tons Absorbed

Research presented by Christopher L. Sabine of the U.S. National Oceanic and Atmospheric Administration suggests that oceans have absorbed just under 120 billion metric tons of carbon generated by human activities since 1800.

Other data presented at the symposium suggest that an additional 20 million to 25 million metric tons of CO₂ are added to the oceans each day.

Symposium participants agreed in a final document that oceanic absorption of carbon should be considered "a beneficial process" that reduces atmospheric concentrations of the problematic gas and "mitigates" its effect on global temperatures.

However, the symposium also pointed out "growing concern" over the biodiversity costs that may eventually be linked to this process, UNESCO said.

Highest Acidity in 20 Million Years

Specifically, symposium participants predicted that the accumulating burden of CO

₂

entering the oceans will lead to the most dramatic changes in pH levels of ocean surface waters observed in the past 20 million years.

Rising acidification lowers nutrient and oxygen levels, "affects many species, and changes the composition of biological communities in ways that are not yet understood or predictable," symposium participants said.

Higher CO₂ and lower pH levels would also curb reproduction of many calcifying organisms, including certain species of plankton and corals, while rising temperatures "pose a serious threat to coral reefs," symposium participants said.

Symposium participants stressed that while the impact of climate change on the world's oceans has been much debated, the direct chemical and biological impact of CO₂ itself has largely been neglected.

The final report from the UNESCO symposium stressed the need for more research, particularly to increase understanding of the changes taking place and their consequences, and to allow for more informed policy decisions in this area.

More information on the UNESCO symposium, including abstracts of scientific research presented during the meeting and the participants' final report, is available at http://ioc.unesco.org/iocweb/co2panel/HighOceanCO2.htm on the World Wide Web. End of article graphic