Saturday, November 15, 2008

Tracking changes in CO2

The NOAA Coral Reef Watch program has a new "ocean acidification" online tool that maps changes in ocean chemistry brought about by rising carbon dioxide concentrations. The information is critical to understanding the long-term threats to coral reefs.

Here's a brief explanation (see NOAA's site for more):

Carbon dioxide dissolves in water - that's how you make a carbonated beverage. Around one-quarter to one-third of the CO2 emissions from human activity each year are absorbed by the oceans. The CO2 react with water to form carbonic acid (H2CO3), reducing pH in the process. That's where we get the term "ocean acidification".

The central concern for coral reefs is that this alters the balance of the common dissolved carbon compounds. The process of "buffering" the pH change consumes carbonate ions (CO3--) which corals and other calcifying organisms use to build their skeletons. So as CO2 levels increase, the proportion of ocean carbonate decreases, and the ability of corals to build reefs decreases. The slower-growing, weaker reefs are then more vulnerable to erosion. This can be seen today in parts of the eastern equatorial Pacific like the Galapagos, where corals do persist but naturally high carbon dioxide levels (from upwelling of high pCO2 deep waters) limit reef growth and ecosystem development.

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