While the impact of increasing concentrations of carbon dioxide in the atmosphere is widely discussed, I have seen rather less attention paid to important chemical changes it causes in the oceans. In particular, that includes how increased atmospheric concentrations of CO2 cause the ocean to become more acidic. (BBC article) Some predictions hold that oceanic pH will fall by 0.4 in the next ninety years or so. Remember that pH is a logarithmic scale: a solution with a pH of 6 is ten times more acidic than one with a pH of 7.
One important consequence of this lowering of pH is that it decreases the amount of calcium carbonate (chalk) that is in solution in the seawater. Calcium carbonate is the primary material from which the hard structures of many marine organisms are made: from shells to coral reefs.
Increased oceanic acidity begins at the poles and progresses towards the equator, where most of the world’s coral reefs – and marine biomass in general – are located. Intuitively, the difficulty of grasping the knock-on effects of such a chemical transition is obvious. Oceanic acidity is likely to affect other biological systems, including the overall distribution of species within and between ecosystems. It is a further reminder of the unpredictable consequences that will result from increasing CO2 concentrations: concentrations that will be double their pre-industrial levels within 45 years, at present rates of growth.