Ocean acidification, the "other carbon dioxide problem," results from the ocean's absorption of CO2 from the atmosphere, which increases the acidity of the ocean and changes the chemistry of seawater. The primary known consequence of ocean acidification is that it impairs the ability of marine animals to build and maintain the protective shells and skeletons they need to survive. Nearly every marine animal studied to date has experienced adverse effects due to acidification. Sakashita said, "Ocean acidification is global warming's evil twin, and CO2 pollution is one of the biggest threats to our marine environment. We need prompt action to curb CO2 emissions to avoid the worst consequences of acidification."
Under the settlement, EPA has agreed to initiate a public process to develop guidance on how to approach acidification under the Federal Clean Water Act. Specifically, EPA will consider a provision of the Act that requires states to identify threatened or impaired waters and set limits on the input of pollutants into these waters. On March 15, EPA was to submit for publication in the Federal Register a notice soliciting public comments on how to evaluate waters threatened by acidification and address the problem. Scientists have confirmed widespread ocean acidification due to CO2 pollution. The Arctic, for example, faces imminent consequences, and areas of the Arctic are expected to become corrosive by 2016.