Ocean pH Standard Falls Short of Protection

The Center for Biological Diversity of San Francisco, Calif., recently petitioned EPA to strengthen the water-quality standard for ocean pH and to publish guidance to help states protect U.S. waters from carbon dioxide pollution.

The oceans cover about 70 percent of the Earth’s surface and absorb about 22 million tons of carbon dioxide each day. Seawater reacts with absorbed carbon dioxide to become more acidic. This process, termed ocean acidification, has many adverse effects, including the impairment of marine organisms’ abilities to build protective shells and skeletons.

In a new report in the journal Science, scientists predict that if human sources of carbon dioxide continue to increase, ocean acidification coupled with global warming will kill the majority of the world’s coral reefs by the end of the century (Hoegh-Guldberg et al. 2007). Already, the pH of the ocean has decreased 0.1 units on average due to anthropogenic carbon dioxide.

If carbon dioxide emissions continue unabated, seawater pH may decrease an additional 0.4 units — more than a 100-percent change in acidity.

According to the Center’s petition, EPA’s water-quality standard is inadequate in the face of ocean acidification. A decline of 0.2 pH — allowed under the current standard — will be devastating to the marine ecosystem. Twenty-five leading scientists researching ocean acidification recently concluded that “a decrease of this magnitude would pose a risk to the physiology and health of a variety of marine organisms” (Caldeira et al. 2007).

“The Clean Water Act is the nation’s strongest law designed to protect water quality,” said Miyoko Sakashita, attorney for the Center for Biological Diversity’s oceans program. “Because ocean acidification is the greatest threat to the water quality of the oceans, EPA has a duty to take steps to address ocean acidification under the Clean Water Act.”

The Center has petitioned 10 coastal states to declare their ocean waters “impaired” under the Clean Water Act due to ocean acidification. Responses to those petitions are pending.

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