If you’ve ever owned or known anyone who’s owned a salt water aquarium, you know that one of the biggest maintenance challenges, especially for novices, is keeping pH levels in proper equilibrium. Most fish species only live within certain ranges. If the pH in your tank gets too high or too low, you end up with a tank full of dead fish.

Image credit: Dani Simmonds

The same thing is true, on a much larger scale, in the oceans themselves. Over billions of years of evolution, the current oceanic ecosystem is dependant on the water, and its pH levels, remaining fairly constant. If the pH of the oceans themselves significantly changed, it could devastate ecosystems everywhere on Earth.

Given that the above is a depressingly apocalyptic scenario, it’s no surprise to learn that it’s actually happening. Over the past 600,000 years or so, the oceans have remained at a pH of approximately 8.2. However, recent studies have shown that since the Industrial Revolution, the pH of the oceans has dropped about 0.1–which indicates a 30% increase in acidity over the past two centuries.

The primary culprit is carbon dioxide emissions. Since the beginning of the industrial revolution, the oceans have absorbed approximately 30-40% of all man-made carbon dioxide emissions. And that absorption is beginning to show.

The basic problem here is one of chemistry. When carbon dioxide dissolves in water, one of the byproducts is carbonic acid (H2CO3). Now, there are many buffer systems in place in the oceans to prevent too great a change in pH. However, over the past 200 years, the increase in carbon dioxide emissions into the atmosphere and, consequently, the oceans, have been so great as to overwhelm the ocean’s natural ability to keep the pH in balance, which is why it has dropped 0.1 so quickly.

The consequences of this drop in pH levels is pretty severe. For one thing, higher acidity in the oceans will literally dissolve the calcium carbonate which forms the shells of clams, oysters, and is the primary chemical component of coral reefs. (For a rundown of the basic chemistry of this, there’s a great explanation here.) If current carbon dioxide emissions continue, then it’s possible that by the end of this century, the oceans may literally be too acidic for coral reefs to exist. The last time the oceans were that acidic, about 65 million years ago, it took two million years for the dissolved coral reefs to recover.

The increasing acidification of the oceans will also hurt pteropods and other types of plankton, rendering them less likely to survive. This would not only effect the ability of the oceans to absorb carbon dioxide, but it could also wreak havoc on the food chain, as this article in Discover points out:

Their populations rapidly decline. At both poles, organisms in decline are being replaced by plankton called flagellates. According to [Oceanographer David] Hutchins, flagellates are not nearly as good at passing their stored energy up the food chain to fish and other higher life forms. “That’s going to disrupt food chains that sustain the kinds of creatures we’re used to seeing at the poles—sea lions, penguins, and whales—and instead promote a microbe-dominated community,” he says.

The destruction of such ecosystems also threatens commercially fished species, such as cod, tuna, and marlin. Depletion of those resources threatens billions of dollars, not to mention diminishing food sources at a time when food prices are already rising.

What can be done to stop the problem of acidification? Well, that’s both easy and difficult. The most effective way to stop the increasing acidification of the oceans is simply to cut carbon emissions–drastically. Current goals to offset climate change–such as capping carbon emissions at double what they are now–are not enough. However, given the politics of carbon emissions, I wouldn’t hold my breath for this to be the primary solution. Unless, of course, we actually get some international cooperation and build orbiting solar power plants–which I am all for.

Another possible solution is the use of quicklime sequestration, which would entail basically pumping millions of tons of limestone into the ocean and heating it up. The resulting chemical reaction would result in making the oceans less acidic. It could also potentially result in the ability for the oceans to absorb more carbon dioxide without compromising pH, which would help inhibit the effects of climate change. The problem, of course, is that geoengineering at that scale would be enormously expensive.

Whatever the solution is, whether it’s cutting emissions, building solar plants, or geoengineering the ocean, if we don’t do something soon, the problem of ocean acidification is going to get worse. And the Earth is an awfully big aquarium for us to let all of our fish die.