Ocean acidification has been called "global warming's evil twin" which apparently admits that if global warming existed as a twin, it would be a good one. Is ocean acidification a problem?







Some of the biggest unknowns hide in biology which is not exactly my field but I have spent whole days with it, too. Concerning the figures that are normally listed and that describe the changing pH of the oceans, I have almost no doubt that they're pretty much correct. See



Since 1751 to 1994, the oceans' pH went down from 8.180 to 8.105 or so. The neutral level of pH is 7.The pH scale is logarithmic: the actual concentration of H3O+ ions is proportional to 10^{-pH} while the concentration of the OH- ions is inversely proportional to the same thing or directly proportional to 10^{+pH}.The changing pH can be traced to the changing concentration of CO2, and the corresponding ions in water, which pretty easily follows the changes in the atmosphere, by Henry's law and some simple chemistry looking at a few chemical reactions, at least in the short run (in the long run, the extra CO2 in the oceans is being consumed). It is not hard to estimate that the pH indeed has changed by something like almost 0.1 in the last 200 years. There are very good reasons why chemistry uses this logarithmic pH scale - simply because in typical situations, the possible concentrations of ions go over many decades - they often change multiplicatively by many orders of magnitude (i.e. their logarithms change linearly) - and their products are often required to be constant for chemical equilibrium.Now, it can be argued that in 100-150 years, the oceans' pH will go to 7.9 or so, under business as usual. It will certainly stay alkaline. But I think that all these qualitative changes are extremely likely, almost obvious. The only question is whether it threatens anyone, or life in the oceans in general. I think that the obvious answer is No. As everyone with an aquarium knows, virtually all fish don't care about the change of pH by 0.5. Most fish actually can live anywhere in pH between 5 and 9.And e.g. ornate rainbowfish can exist in water as acidic as orange juice, see an article in Australia's ABC , which is 3.5 or so. But the Coca-Cola is more acidic, near 2.5, and the fish could have some trouble to live in it. Nevertheless, the concentrations of H3O+ and OH- ions in orange juice - which is still OK for those fish - differ by 6 orders of magnitude from the concentrations in the current ocean! The concentrations of ions are tiny, anyway: it's the water itself that matters most. You shouldn't miss the forest behind the tree.Now, these were fish. Obviously, no problems await them. I had to look at other things such as plankton, coral reefs, etc. You will find some diversity of the preferred values of pH and a shift of pH by 0.2 could affect the composition of the species in the ocean.However, it's surely not able to threaten any major family of organisms in the ocean. In average, I think that the marine life would enjoy a drop of pH from 8.1 to 7.9. It shouldn't be too surprising that I think that the optimum pH for an average marine organism is 7.0 - the pH neutral level - and we have no chance to drop this low by burning fossil fuels because that would essentially need to multiply the CO2 concentrations in the air by a factor of ten. (It's actually closer to 100 because there are many other ions aside from the CO2-related ones in the ocean.)To summarize, I am 99.99% certain that there is no problem of "ocean acidification" worth talking about. Every year, the average pH is changing by 0.002 or so. No single organism with lifetime comparable to human life or shorter can possibly detect the change. Only the systems - coral reefs - that live for a longer time need to be watched. But there are good reasons to be certain that the slight drop of pH has no significant negative impact on them, either.