Ocean Acidification

Ocean acidification, including the waters of Puget Sound, is intensifying with grave results. Caused by carbon dioxide—also one of the major causes of global climate change— the ocean absorbs about a quarter of the CO2 humans release into the atmosphere.

One effect of acidification is to undermine the ability of saltwater species to build shells and skeletons, affecting such ocean creatures as crabs, corals, sea urchins, and shellfish—scallops, mussels, clams, and oysters. Acidified waters also affect fish in their behavior and can simply kill some marine life, such as oyster larvae on the Oregon coast. Especially when combined with warmer temperatures, acidified ocean water causes sea urchin larvae to change shape, the metabolisms of squid to slow down, and the threads that hold mussels to rocks to fail. Less obviously and with much greater import, acidification is harming plankton, the tiny plants and animals that are the foundation of the ocean’s food chain. A polar bear does not eat plankton but it depends upon a food web that does.

Ocean acidification also effects how the ocean responds to nitrogen. Nitrogen pollution acts like a fertilizer, causing massive growths of marine algae, such as in Puget Sound. As this algae grows, it temporarily decreases the levels of marine CO2, which makes the water less acid. However, when the algae die deep below the surface, the rotting algae returns this same CO2 into the water, making it more acid. In this way, the human sources of nitrogen into Puget Sound are making an already acid ocean even more acid.

Photo from National Oceanic and Atmospheric Administration (NOAA), which has found evidence that ocean acidification is dissolving the shells of free-swimming marine snails called pteropods, which provide food for salmon, mackeral, and herring.