California Coastal Commission

Ocean Acidification

Kelp forest, by Chad King
Kelp Forest, by Chad King    

Ocean acidification is the global trend of the ocean absorbing increasing amounts of carbon dioxide from the atmosphere, resulting in a decreasing seawater pH. This does not mean that the ocean is turning into an "acid." It does however mean that the ocean is becoming more acidic—in other words the pH level of seawater is moving closer to the acid end of the scale.

Ocean acidification happens when carbon dioxide reacts with water to form carbonic acid. Since humans have been releasing increasing quantities of carbon dioxide into the atmosphere through the burning of fossil fuels, the rate of ocean acidification has increased. In spring of 2013, the atmospheric concentration of carbon dioxide reached 400 parts per million, higher than the earth has seen in more than 800,000 years. In 2017 we passed 410 parts per million. Since people started burning fossil fuels during the Industrial Revolution, the global average pH of the surface ocean has decreased by 0.11 pH units, which is a 30% increase in acidity. If carbon emissions are not reduced, by the end of the century ocean pH is predicted to be lower than the earth has seen in 20 million years.

What does this mean? The ocean acts as a carbon "sink," buffering our atmosphere from what would be much higher concentrations of carbon dioxide. However, the rate of change in ocean pH is so much greater than what the earth has historically seen, some marine organisms will not adapt to their new environment. Calcifying organisms, such as shellfish and corals, are particularly vulnerable to ocean acidification, which impedes the ability of these organisms to produce and maintain their shells. Some negative impacts have already been documented, such as farmed oyster larva in the Pacific Northwest unable to form shells during low pH events. Laboratory experiments show that elevated carbon dioxide alters clownfish behavior, making them potentially more vulnerable to predators. Coral reefs, already impacted by rising ocean temperatures, are further stressed by ocean acidification.

How do we address this problem? The ultimate answer is to reduce our carbon dioxide emissions. On a personal level, commit to conserving energy wherever possible. Walk, bike, ride public transit, and carpool instead of driving alone. Reduce your waste by thinking before you buy something. Conserve electricity, gas, and water at home and work. Get involved in your community to support decisions that help fight ocean acidification. And help the ocean cope by reducing other pressures on marine organisms such as by only consuming seafood that has been fished or farmed sustainably, picking up trash in your neighborhood and at the beach, practicing smart use of pesticides and fertilizers, and cleaning up after pets.

In April 2016, the West Coast Ocean Acidification and Hypoxia Science Panel, a bi-national team of 20 scientific experts from California, Oregon, Washington, and British Columbia, released a report of Major Findings, Recommendations, and Actions. This report stresses that ocean acidification is expected to grow in intensity with far greater impacts to come, acknowledges that it requires global solutions to reduce carbon dioxide emissions, and urges coastal managers to take action to improve local conditions contributing to declining water quality. Much more can be found in the report.

Learn more about ocean acidification:

Resources for educators:

Ocean Acidification explained as a Comic:

Shell Shock Comic Page 1
Shell Shock Comic Page 2
Shell Shock Comic Page 3

This comic was co-produced by Years of Living Dangerously, a SHOWTIME climate change documentary series, and Symbolia, a magazine where "comics and journalism meet."
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