July 01, 2016

Acid oceans and the increasing threat to U.S. fisheries and coral reefs

Mary Greene and Eric Andreas


Ocean acidification results from decreases in the pH of the Earth’s oceans caused by the natural uptake of carbon dioxide. In a nutshell, here’s how it works: The pH scale is a measure of acidity that ranges from 1 to 14, where 7 is considered neutral. Any pH reading that is higher is basic, anything lower is acidic. When carbon dioxide dissolves in water, it creates carbonic acid. In essence, the more carbon dioxide humans pump into the atmosphere, the more it is absorbed by the oceans, resulting in an increase in the production of carbonic acid, which in turn increases ocean acidity. Since the industrial revolution, there has been a 30 percent increase in ocean acidity. NOAA PMEL Carbon Program, A Primer on pH.

The deadliest impact of this dramatic rise in acid levels is felt by organisms that form calcium carbonate shells, skeletons, or internal structures, such as coral reefs, shellfish, and planktonic species. Increased acidification reduces calcification rates, thereby inhibiting the growth of the very structures they need to survive. J. A. Kleypas et al., Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers (June 2006). Scientists anticipate that this brewing crisis will have lasting detrimental effects on shellfish, aquaculture, and coral reef ecosystems and could ultimately disrupt the food supplies of fish, marine mammals, and even humans. R. Craig, Dealing with Ocean Acidification: The Problem, the Clean Water Act, and State and Regional Approaches, 90 Wash. L. Rev. 1585, 1590 (Feb. 2016). The problem is real and getting worse. Here in the United States, ocean acidification threatens both commercially important fisheries and valuable, endangered coral species.

Impacts to fisheries

Ocean acidification affects not only commercially important shellfish such as oysters, clams, scallops, lobster, crabs, and shrimp, but also smaller planktonic creatures such as pteropods, which play a vital role in the marine food web and are eaten by everything from tiny krill to whales. NOAA PMEL Carbon Program, What Is Ocean Acidification. In Alaska, Oregon, and Washington State, the combination of upwelling (which brings cold and more acidic waters from the ocean floor to the surface) and ocean acidification may already have put numerous fisheries at risk. In Alaska, this combination of upwelling and atmospheric absorption-related acidification is stunting the growth of red king crabs and tanner crabs, which may very well result in economic losses on the order of hundreds of millions of dollars. See Craig at 1600. In Oregon and Washington States, oyster farmers have noticed significant declines in oyster populations and larvae die-off. Ocean acidification is the likely cause of this reduction. C. Kennedy, NOAA, An Upwelling Crisis: Ocean Acidification.

Just as concerning, a recent study found that ocean acidification impacts the shell condition and survival of pteropods in Puget Sound in Washington State. D. Shallin Busch, et al., Shell Condition and Survival of Puget Sound Pteropods Are Impaired by Ocean Acidification Conditions. Pteropods play a vital role in the marine web as an important food source for Pacific Northwest salmon and herring. This study emphasizes that ocean acidification not only has far-reaching impacts on economically valuable fisheries, but also on the entire marine ecosystem.

Not surprisingly, ocean acidification is more than a West Coast problem. Increased acidification has been identified in the Chesapeake Bay, Long Island Sound, Narragansett Bay, and throughout the Gulf of Mexico, all of which have important commercial fisheries.

Impacts to coral reefs

Coral reefs are also seriously threatened by ocean acidification as they build massive skeletons of calcium carbonate. In fact, a recent study suggests that reefs in the normally pristine waters surrounding the Florida Keys are eroding faster than they can grow as a result of ocean acidification. N. Muehllehner et al., Dynamics of Carbonate Chemistry, Production and Calcification of the Florida Reef Tract (2009–2010): Evidence for Seasonal Dissolution. As the home to 25 percent of all marine species, coral reefs play a vital role in the ocean’s ecosystem. USGS, U.S. Coral Reefs-Imperiled National Treasures. Within the waters of the United States, coral structures cover more than 4 million acres of the sea floor spanning the Atlantic Ocean, Gulf of Mexico, Caribbean, and Pacific Ocean and contribute hundreds of millions of dollars to the United States fishing industry every year, in addition to the billions of dollars generated through tourism alone. Clearly, the continued destruction of these reefs would have widespread ecological and economic impacts well beyond our borders.


Surprisingly, few cases pertaining to ocean acidification have been addressed by the courts. In 2007 the Center for Biological Diversity (CBD) sued the U.S. Environmental Protection Agency (EPA) for violating section 303(d) of the Clean Water Act in Center for Biological Diversity v. U.S. E.P.A., 90 F. Supp. 3d 1177 (W.D. Wash. 2015). The CBD argued that because pH levels in Washington State’s coastal waters were not in the range required by state water quality standards, these coastal waters should be placed on the impaired waters list. Ultimately, CBD settled with EPA. The settlement, however, did not require EPA to list the waters as impaired, nor did it result in any rulemakings. It called on EPA to agree to take comments about whether and how to address ocean acidification and to issue guidance as to how states should take action to address ocean acidification. In the future, environmental groups may bring other suits under the Clean Water Act. In the meantime, these groups are already looking to the Endangered Species Act for further relief, arguing that acidification justifies a listing for a threatened species or harms organisms that are currently listed as endangered. CBD, Petition to List Acropora Palmata (Elkhorn Coral), Acropora Cervicornis (Staghorn Coral), and Acropora Prolifera (Fused-Staghorn Coral) as Endangered Species under the Endangered Species Act. Ultimately, ocean acidification is a very real threat to marine ecosystems everywhere. It is not only of concern to the United States but a global issue with far-reaching impacts that must be addressed accordingly at a global scale.

Mary Greene and Eric Andreas

Mary Greene and Eric Andreas are attorney-advisors in the Department of the Interior, Division of Mineral Resources. Their views presented herein are theirs alone and do not necessarily reflect those of the Department of the Interior or any other federal agency.