Ocean Acidification and Potential Toll on Marine Life

An excellent new article on ocean acidification was published last week in Science as part of a special section of the oceans, Richard Kerr, Ocean Acidification Unprecedented, Unsettling, 328 Science 1500-1501 (subscription required). The piece is appropriate for undergraduate, graduate and law students and provides a really good summary of research to date on “the other carbon dioxide problem” associated with burgeoning greenhouse gas emissions.

Among the take-aways of the article:

  1. While there are some certainties in this field, including the fact that carbon dioxide emissions are resulting in gigatons of acid lowering the pH of the world, substantial uncertainties remain in terms of ecosystem impacts. Notably, there’s nothing in the geologic record as severe as the current plunge in pH. Laboratory studies, however, have revealed that corals always do poorly, though the impact on other organisms is more mixed. For example, a recent study found a 30% reduction in shell thickness of one species of roam in the Southern Ocean, and most other non-coral calcifiers also demonstrate slowing carbonate building. However, a few species, including certain coralline red algae and echinoderms have shown increases in carbonate building rates;
  2. Ocean pH is now lower than it has been for 20 million years, and is heading lower. Current projections are that pH will drop from 8.2 pre-industrial to 7.8 by the end of the century, which would increase the surface oceans acidity by about an average of 150%;
  3. The closest analog to what is occurring currently in terms of ocean acidification is the Paleocene-Eocene Thermal Maximum (PETM) 55.8 million years , with comparable amounts of of carbon dioxide and methane emissions (which quickly oxidizes to carbon dioxide). The startling contrast is that the rate of release of greenhouse gas emissions in the current era is 10x faster than in the PETM. This likely will make a profound difference in terms of impacts. In a thousand year period, sediments in the oceans can neutralize added acid, which explains why the massive release of GHGs during the PETM only resulted in the extinction of tiny shell-forming organisms on the deep floor.  By contrast, “today’s emissions are so rapid that they are piling up in surface waters;
  4. While there is some funding for ocean acidification research, including $5.5 million on the 2009 Federal Ocean Acidification Research & Monitoring Act, much more is required for development of a National Ocean Acidification Program in the United States.

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