Burning Fossil Fuels Acidifies Oceans, Erodes Coral Reefs

BOULDER, Colorado, July 5, 2006 (ENS) - The emission of carbon dioxide from burning fossil fuels worldwide is making the oceans more acidic, eroding the calcium in corals and other marine organisms, the way osteoporosis thins human skeletons. New research published today predicts that calcification rates will decrease as much as 60 percent within the 21st century.

The report, "Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers," is authored by a group that includes scientists from Australia, Canada, France, Germany, Japan, Monaco, New Caldonia, and the United States. It documents that oceans worldwide absorbed about 118 billion metric tons of carbon between 1800 and 1994. This is altering ocean chemistry more than at any time for eons, the scientists say.

"This is leading to the most dramatic changes in marine chemistry in at least the past 650,000 years," says Richard Feely, one of the authors and an oceanographer at the National Oceanic and Atmospheric Administration's (NOAA) Pacific Marine Environmental Laboratory in Seattle.

Oceans are naturally alkaline, and they are expected to remain so, but the interaction with carbon dioxide is making them less alkaline and more acidic.

The increased acidity lowers the concentration of carbonate ion, a building block of the calcium carbonate that many marine organisms use to grow their skeletons and create coral reef structures.

Reef-building coral, Dendrogyra cylindrus, in the Florida Keys National Marine Sanctuary (Photo by Cmdr William Harrigan courtesy NOAA)

"It is clear that seawater chemistry will change in coming decades and centuries in ways that will dramatically alter marine life," says Joan Kleypas, the report's lead author and a scientist at the National Center for Atmospheric Research in Boulder.

"But we are only beginning to understand the complex interactions between large-scale chemistry changes and marine ecology. It is vital to develop research strategies to better understand the long-term vulnerabilities of sensitive marine organisms to these changes," Kleypas said.

The 60 percent estimated decrease in calcification is acknowledged to be "oversimplified" and it may not fully consider other environmental and biological effects such as rising water temperature and biological adaptation, organism fitness, community structure, and ecosystem functioning, the report states.

"Any of these factors could increase or decrease the laboratory-based estimates, but it is certain that net production of CaCO3 [calcium carbonate] will decrease in the future," says the report.

This report follows an April 2005 workshop funded by the National Science Foundation and NOAA, and hosted by the U.S. Geological Survey Integrated Science Center in St. Petersburg, Florida.

Experimental studies, such as those conducted by one of the report's authors, Chris Langdon at the University of Miami, show that coral calcification consistently decreases as the oceans become more acidic.

This means that corals will grow more slowly, or their skeletons will become less dense, a process similar to human bone-thinning known as osteoporosis.

"This threat is hitting coral reefs at the same time that they are being hit by warming-induced mass bleaching events," Langdon says. Mass bleaching occurs when unusually warm temperatures cause the coral to expel the colorful microscopic algae that provide the coral polyps with food.

Many calcifying organisms - including marine plankton such as pteropods, a planktonic marine snail - are affected by the chemistry changes.

The pteropods are the clear snail-like shells shown with other tiny marine organisms and fragments of larger ones. (Photo courtesy NOAA)

"Decreased calcification in marine algae and animals is likely to impact marine food webs and has the potential to substantially alter the biodiversity and productivity of the ocean," says Victoria Fabry of California State University, San Marcos, who is another of the report's authors.

Cold-water reefs may be particularly threatened by ocean acidification, the authors warn. These extensive structures provide habitat for many important fish species in the coastal waters of Alaska.

Lisa Robbins of the U.S. Geological Service Center for Coastal and Watershed Studies and Chris Sabine of the Pacific Marine Environmental Laboratory (PMEL) also co-authored the report.

The ocean helps regulate atmospheric carbon dioxide (CO2) concentrations through air-sea exchange. The rate of exchange can be determined by making high resolution measurements on research and other vessels ships that may be fitted with instruments as required. The PMEL CO2 Program currently maintains instruments that collect CO2 information from a variety of ships as they transit the oceans.

The report recommends new educational and media outreach programs to inform the public about ocean acidification and its impacts on marine calcifiers. With relatively few specialists, the topic is new and the science can be confusing, the report acknowledges.

Closeup of coral skeletons from colonial coral. (Photo by Dr. James P. McVey courtesy NOAA)

Local communities should be encouraged to better understand the impacts of climate change on marine ecosystems to increase stakeholder support for and participation in marine ecosystem conservation, the authors recommend.

They advise workshops and training programs with communities to provide access and orientation to current research findings and data; planned development and distribution of educational materials and displays; fostering community involvement in conservation and restoration projects; and hosting two-way discussions with stakeholders to improve mutual understanding of resource needs and management goals.

The authors suggest developing partnerships with K-12 schools, Centers for Ocean Science Education Excellence, the National Sea Grant Program and community organizations can use educational resources and encourage stewardship through service learning projects that involve teachers and parents.

Education programs should focus on translating the latest research into activities that help students understand the complex interactions of climate and marine ecosystems and the need for scientists from diverse backgrounds. The authors hope that these activities be coordinated through the proposed National Ocean Education Office recommended by the U.S. Commission on Ocean Policy of 2004.

The report, "Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers," is found online at: http://www.ucar.edu/communications/Final_acidification.pdf