Ocean Acidification

Many people we met at the tide pools talked about the changes they have seen in their lifetime. Some talked about the relative abundance of marine wildlife relative to the 1970s, when many environmental protection laws were put in place. Others complain of a dearth of biodiversity and marine life in general relative to 50 years ago.

I grew up tide pooling in Half Moon Bay, on the San Mateo coast, so I don't know the longer history of marine life in the Santa Monica Bay. However, I do feel an urgency to show Iris tide pools whenever the opportunity presents itself because I fear she will not be able to show them to her children. Why?

Ocean acidification due to the huge amounts of carbon dioxide we are pumping into the atmosphere. When carbon dioxide, CO2, is dissolved in water, it forms carbonic acid, H2CO3, which loses a proton, H+, immediately. Carbonic acid is even more acidic than white vinegar. Put a few drops of vinegar on sea shells to see what happens.

It is well established among researchers that the uptake of increased amounts of carbon dioxide will make ocean water more acidic as the gas dissolves to create carbonic acid. Ocean chemistry is changing 100 times more rapidly than in the 650,000 years that preceded the modern industrial era and since the late 1980s, researchers at Scripps Oceanography and others have recorded an overall drop in the pH of the oceans from 8.16 to 8.05.

The California coast is less vulnerable, relative to some tropical locales, to ocean acidification because of the strong upwelling of deep ocean water offshore. The deep water is colder and more nutrient-rich than the surface water. In effect, the deep ocean circulation is like a tape recorder, and we are replaying the CO2 levels from 50 years ago, when those parcels of water were last at the surface.

Yet, the upwelling water is already so acidic that the marine life off the coast of California is stressed. They have difficulty forming shells and skeletons, causing them to be more susceptible to disease. Phytoplankton blooms are occurring with greater frequency and lasting for longer periods due to the enhanced CO2. The commercial Dungeness crab season has shrunk to two weeks. The list of effects goes on and on.

If this is happening with 50 year old atmospheric CO2 levels (310 parts per million), what happens when today's surface ocean water (380 ppm CO2) resurfaces?

Further reading:

• Rising Acidity Is Threatening Food Web of Oceans
• U.S. Pacific Coast Waters Turning More Acidic
• Global scientists draw attention to threat of ocean acidification
• Fishermen Make Mad Dash For Dungeness Crab