Ocean Acidification

[sinimod]

Discussion has been dominated by the grim prospects of global warming. However, there is another topic that is vitally important to the health of this planet, ocean acidification. The importance of this topic cannot be over estimated, and we should be frequently reminded of just what the possible future effects could be.

Due to the rapid increase in the concentration of atmospheric carbon dioxide from the use of fossil fuels, the oceans are rapidly becoming more acidic. Keeping in mind that, in addition to climate change and its many profoundly deleterious effects on the global ecology, the world’s oceans are experiencing dramatic changes in pH levels at rates possibly not experienced since early in the history of the planet when volcanism was far more prevalent. Ocean acidity is increasing at a rate more than 100 times faster than the natural variation experienced over the last two to three billion years, due to a concomitant and proportional increase in the concentration of atmospheric CO2, inadvertently released at the hands of humanity. If, as IPCC emission scenarios and general circulation models suggest, the atmospheric concentration of CO2 reaches 800 ppmv by the end of the 21st century, surface water dissolved inorganic carbon could increase by more than 12% and the carbonate ion concentration could decrease by almost 60%, with a corresponding decrease in pH of 0.4 pH units in surface water (Feely et al., 2004).

Most shallow marine organisms construct their shells with high-magnesium calcite or aragonite, both metastable minerals at earth surface temperature and pressure. If oceanic pH levels reach the predicted values, it could surpass the stability fields for even the biogenically induced precipitation of these minerals, even in tropical oceanic latitudes, where warmer water favors supersaturation with respect to these minerals. This means that biological calcification of the shells of most marine organisms, many of which have already had their physiology deteriorate due to increased shallow ocean water temperatures, might not be chemically possible. As marine ecosystems are extremely sensitive to temperature and pH changes, the prospect of continual deterioration and possible destruction of shell-constructing marine organisms could mean the break down of the entire ocean ecosystem. I don’t think I have to spell out to anyone how utterly disastrous that would be.