The parliamentary debate on the connection between CO2 emissions and climate change has overlooked an independent and equally serious problem, the increasing acidity of our oceans. Last December, the respected journal "Oceanography" published projections (see graphic below) for this rising acidity, measured by falling pH , through to the end of the century .

The chemistry is simple - CO2 dissolved in water forms carbonic acid, the same acid that eats out limestone caves from our mountains. CO2 in the atmosphere has increased from 278 ppm in pre-industrial times to 390 ppm today (late 2010). During this time, the amount of CO2 dissolved in the ocean has risen by more than 30%, decreasing the pH of the ocean by 0.11 units. As with CO2 and global warming, there is a lag between cause and effect (see Ref A). That means we are yet to see the worst of the problem. According to the Australian Antarctic Division of our Department of the Environment, "even if all carbon emissions stopped today, we are committed to a further drop of 0.1 to 0.2 pH units" . However, if CO2 is allowed to rise along a business as usual trajectory, they are concerned that pH will "fall by 0.5 pH units by 2100, a 320% increase in acidity".

The close relationship between CO2 in the atmosphere, CO2 dissolved in the ocean, and the effect of the latter in falling pH, is illustrated by the graph below.

Source: Feely, Doney and Cooley, Present Conditions and Future Changes in a High-CO2 World, published in the journal Oceanography, issue 22 p. 36-47, using Mauna Loa data from the US National Oceanic and Atmospheric Administration and Aloha data from the University of Hawaii

The implications of this are frightening. Coral reefs, and the exoskeletons of countless tiny marine creatures, are formed from the same substance, calcium carbonate, that is removed from limestone by CO2 dissolved in water. The photo below left shows healthy phytoplankton. The photo below right shows the damage to the same creature under conditions expected by the end of the century . These and creatures like them are at the base of an ocean food chain. If they are lost, it is not just biodiversity we are loosing, but our food supply as well.

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The implications of this are frightening. Coral reefs, and the exoskeletons of countless tiny marine creatures, are formed from the same substance, calcium carbonate, that is removed from limestone by CO2 dissolved in water. The photo above shows healthy phytoplankton. The photo above right shows the damage to the same creature under conditions expected by the end of the century . These and creatures like them are at the base of an ocean food chain. If they are lost, it is not just biodiversity we are loosing, but our food supply as well. The exoskeletons of phytoplankton are constructed from a form of calcium carbonate known as aragonite. For these creatures to absorb this mineral from seawater, the latter needs to be saturated in aragonite. In the study published in Oceanography, it is projected that in the Arctic Ocean "aragonite undersaturation will start to occur by about 2020" . In the Southern Ocean, there is already evidence of harm. According to William Howard of the Antarctic Climate and Ecosystems Cooperative Research Centre in Hobart, shells of one species of foraminifera (Globigerina Bulloides) are 30 to 35 percent thinner than shells formed prior to the industrial period . For corals like those in our Barrier Reef, the outlook is grim. They are threatened with destruction on two fronts, both caused by CO2 emissions. Not only do increased ocean temperatures bleach coral by forcing them to expel the algae which supplies them with energy (see photo at right) , but increased ocean CO2 reduces the availability of aragonite from which reefs are made.