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Study: Rising Carbon Dioxide in Oceans Threatens Coral Reefs; Effects to Ripple Through Food Chain News Service
July 5, 2006 15:31 EST

WASHINGTON, D.C. -- Elevated levels of carbon dioxide emissions are affecting not only the atmosphere, but also oceans and sea life, according to a study issued July 5 by the National Center on Atmospheric Research (NCAR).

The report concludes that emissions from burning fossil fuels are altering ocean chemistry to the degree that coral reefs will have a diminished capacity to grow. Coral reefs function as the breeding ground for important species at the bottom of the food chain, so their depletion could have serious affects on many forms of ocean life, according to Impacts of Ocean Acidification Coral Reefs and Other Marine Calcifiers.

The oceans absorbed approximately 118 billion metric tons of carbon since the early 1800s and the beginning of the Industrial Age. This interaction with carbon dioxide is making the naturally alkaline ocean waters more acidic. The higher levels of acidity lower the concentration of carbonate ion, a building block of calcium carbonate, which many marine organisms use to grow their skeletons and create coral reef structures.

"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 Pacific Marine Environmental Laboratory (PMEL) of the National Oceanic and Atmospheric Administration (NOAA).

Experimental studies have shown that the marine organisms dependent on calcium carbonate grow more slowly as the oceans become more acidic. Consequently, reef structures will become threatened because corals will be unable to build reefs at a pace to keep ahead of natural forces of erosion.

These threats come as coral reefs are under stress from mass bleaching events brought on by overly warm temperatures, which cause the coral to expel the microscopic algae that provide the coral polyps with food.

The chemical changes will affect many calcifying organisms such as pteropods, a planktonic marine snail, which is an important food source for salmon, mackerel, herring and cod, the report predicts,

"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.

Calcification rates could decrease by 60 percent in this century, the report projects, and suggests a number of different avenues for further research. The report says research must focus on both the potential responses of marine organisms to increased oceanic carbon levels and the potential impact throughout marine ecosystems.

The report was produced as a result of a workshop funded by the National Science Foundation and NOAA, and hosted by the U.S. Geological Survey’s (USGS) Integrated Science Center in St. Petersburg, Florida.

The conclusions of the study are attributed to the authors, not to the National Science Foundation, NOAA or USGS.