Science speaks: ocean acidification

a stock photo shows coral bleaching
Coral bleaching is just one of many detrimental impacts of ocean acidification on marine ecosystems.

The Science Speaks blog series offers a deep dive into science, technology, and innovation topics on the minds of the public. The series explains focal topics through relatable analogies and asks readers to consider key opportunities, explore avenues for advancing gender equity and equality, and answer the ultimate question: Why should we care? 

I was always saddened by The Giving Tree, a 1964 story about the friendship between a child and a tree. The tree happily hands over pieces of itself—apples, branches, and trunk—to benefit the child from adolescence through adulthood, but by the end of the story, a stump is all that remains. Despite its terrestrial setting, The Giving Tree could be taken as a cautionary tale about ocean acidification.

As its name suggests, ocean acidification is the process by which the ocean slowly becomes more acidic as it dissolves carbon dioxide from the atmosphere. On the surface, this phenomenon sounds like a helpful way of trapping a potent greenhouse gas. But the ocean—like the Giving Tree—will ultimately suffer as a result…and so will the people who depend on a healthy ocean, including millions of women and girls.

Ocean acidification is the result of simple chemistry. Carbon dioxide dissolves in water to form carbonic acid, which, like all acids, can dissociate into its chemical components. From the acidification perspective, the most important of these components are hydrogen ions. The higher the concentration of hydrogen ions, the more acidic the water. Since the beginning of the Industrial Revolution, the ocean has absorbed 525 billion tons  of atmospheric carbon dioxide, resulting in a nearly 30% increase  in hydrogen ion concentration. These statistics are the result of fossil fuel burning, deforestation, and other carbon dioxide-emitting activities.

Just as the Giving Tree surrenders its branches at great personal cost, so, too, does the ocean when it absorbs carbon dioxide. Aquatic species with calcium carbonate shells (like crustaceans, mollusks, and corals, just to name a few) struggle to build those shells because carbonate availability decreases in the presence of excess hydrogen ions. If the ocean becomes too acidic, existing shells may start dissolving. Acidification can also induce physiological changes, such as slowed metabolic functions in squid, faulty predator detection in fish, or bleaching of coral reefs . These changes to aquatic systems and species could cause marine ecosystems to collapse, making the ocean the equivalent of the Giving Tree’s stump.

U.S. government efforts to combat the climate crisis relate to each of these goals. The State Department is advancing policies to conserve and sustainably use the ocean and its resources while catalyzing global action to tackle acidification, among other ocean challenges. Central to these policy and programmatic efforts at the State Department and beyond is the empowerment of women and girls to strengthen the adaptive capacity  and resilience  of communities. Meanwhile, agencies are expanding research on ocean acidification, monitoring acidification on the coasts, and building adaptation strategies.

I never thought The Giving Tree could be anything more than a children’s story about friendship and greed, let alone a subtle warning about marine resources. How could ocean acidification affect your life?

U.S. Department of State, 31 January 2022. Full article.

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