Ocean Acidification

When it comes to the oceans and carbon dioxide, there’s good news and bad news. To date, the world’s oceans have absorbed nearly 1/3 of the excess carbon dioxide emitted as a result of anthropogenic activities. That may be good news for the atmosphere, but scientists and policymakers are increasingly concerned about the side effect of carbon dioxide absorption: ocean acidification.

Since the industrial revolution, ocean pH has gone down by 0.1 units, which translates into a 30 percent surge in acidity. Scientists predict that pH will go down another 0.14 to 0.35 units by the end of this century. Accompanying the lower pH are lower saturation points of minerals such as calcium carbonate, the primary skeletal material of marine organisms that form the basis of ocean food webs, such as phytoplankton and coral reefs. As the ocean becomes more acidic, calcium carbonate begins to dissolve. The shift in ocean chemistry is so profound that the shells will literally dissolve off the backs of some organisms under the ocean conditions predicted for 2100.

The rapid change in seawater acidity is almost unprecedented. Marine life has survived large climate and acidification variations in the past, but the projected rates of climate change and ocean acidification over the next century are much faster than experienced by the planet in the past, except for rare, catastrophic events in the geological record.

BioScience 57: 822, November 2007