Ocean Acidification and the bleaching of Spongebob Squarepants

So basically things aren't looking too good for Spongebob Squarepants and his buddies. The reason being that, all of this carbon dioxide we're pumping into the air is doing some serious shit to the oceans. However in this case, it's less to do with the usual greenhouse effects, but more to do with the ocean's role as a carbon sink. Anyway, it's an interesting and important sidebar to the CO₂ equation, and one that I've looked into a bit more lately as I prep myself for potential topics of discussion in a new course I'm working on.

In essense, the oceans of the world have been changing slowly, not only from a temperature and salinity point of view, but also from a pH point of view. In fact, between the mid 1700s (roughly when the Industrial Revolution started) to present day, the approximate mean ocean pH values have been decreased from 8.25 to 8.14. This is why you hear the term "ocean acidification", although to be technical, the ocean is not actually "acidic" (needs to be less than pH 7.0 for that proper label).

This change might not sound like a lot, but when you consider that the pH scale is a log scale, that .11 difference is akin to a startling 29% increase in H⁺ ions. And how the pH is altered by CO₂ is nicely explained at wikipedia:

When CO₂ dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species : dissolved free carbon dioxide (CO_{2 (aq)}), carbonic acid (H₂CO₃), bicarbonate (HCO₃^-) and carbonate (CO₃^2-). The ratio of these species depends on factors such as seawater temperature and alkalinity.

The overall effect, of course, is that all of this dissolving CO₂ will increase H⁺ concentration in the ocean, leading to the aforementioned change in pH. And although, the irony is that this might actually be a good thing in the greenhouse context, it's not so good for the calcifying organisms that inhabit the waters.

Hmm... "calcifying organisms?" Probably not a term you come across everyday (try working in, "So hows'about them calcifying organisms" into your next dinner conversation), but this basically includes organisms like Spongebob, whose delicate structure is primarily made of calcium carbonate and is essentially viable under conditions where the carbonate ion is supersaturated in the water.

However, under the more acidic conditions, chemical equilibrium pushes the oceanic carbonate amounts down, which can result in chemistry that essentially goes: "Hey, where did all the carbonate go in the water? Let's put it back into the water by dissolving the stuff from our shells and skeletons. I'm such a good sponge!"

Obviously, this causes a serious breakdown of these aforementioned structures. In fact, one of the more notable outcomes of this is the current bleaching of coral reefs, which is why we have the silly graphic at the top of the page.

In any event, it's certainly something that merits cause for concern, especially when you consider that the most recent peered reviewed papers suggest a potential drop of a further 0.3 to 0.4 units by 2100 - alarming because this is indicative of a net 100% to 250% increase in H⁺ ions.

As Spongebob once said, "Good people don't rip other people's arms off." - there's a metaphor in there somewhere.

(note that the New Yorker also had a nice piece on this, sans Spongebob of course).