The Great Barrier Reef

The chemistry of the world’s oceans is changing as they absorb growing amounts of anthropogenic CO₂. The average pH of the oceans has dropped .1 units, from 8.2, and is expected to fall another .3 to .4 pH units if carbon dioxide levels reach the projected 800 parts per million by the end of the century.

Current research suggests that ocean acidification will have dire consequences for marine life, especially organisms that use calcium carbonate to build their shells and exoskeletons. This includes microscopic algae and plankton at the bottom of the food chain, as well as shellfish and corals. Their survival is critical to the health of the ocean ecosystem as well as commercial fisheries and the tourism trade. Lowering the pH of seawater may also slow the rate at which the oceans take up carbon dioxide from the atmosphere–making the planet even warmer.

The severity of the problem is just starting to be addressed. Governments are allocating more money to study ocean acidification and scientists from around the world are working to coordinate their research methods and standardize their experimental protocols. They are studying ocean acidification on a variety of fronts — in single-species laboratory experiments, in ocean environments where pH is naturally low, and by analyzing past ocean acidification events to understand how the ecosystem will respond to rising atmospheric carbon dioxide levels.

While global warming may still seem like an abstract idea, its impact on the oceans and global fisheries has the potential to mobilize the public in a new way to demand limits on carbon dioxide emissions and develop a clean energy infrastructure.

Pteropods, or sea butterflies, are also threatened by lower seawater pH

ocean acidification makes it harder for some species of coccolithophore to build their protective plates