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Ocean acidification refers to the ongoing decrease in the pH of the Earth's oceans. Think the corals in your new reef tank have not been affected? Think again! Miriam from The Oyster's Garter gives us the lowdown on how to preserve life in our oceans. Here's everything you wanted to know about ocean acidification (but were afraid to ask.)

For more on how to help, check out her blog.

Ocean acidification will make off with your children! It will come after you in the night! It's not safe until its head is mounted on my wall! KILL THE BEAST!

Ooops. Wrong movie. But ocean acidification has received a lot of high-profile attention lately, most notably with an editorial in the New York Times. The claims are flying every which way - ocean acidification will kill all the coral reefs, ocean acidification will make the oceans a barren wasteland of jellyfish, ocean acidification will even level the blood-thirsty Humboldt squid.

So here's your handy guide to ocean acidification, and how it might affect coral reefs in particular. I kept it short and semi-sweet, but if you'd like more details or citations just ask!

What is ocean acidification, and why is is happening?

Ocean acidification is a side effect of burning tons of CO2. As CO levels rise in the atmosphere, more and more CO2 gets dissolved in the ocean. Carbonate ions keep the oceans basic, but when there's lots of dissolved CO2 running about the CO2 binds with the carbonate. The carbonate gets taken out of action, and the ocean becomes more acidic. (Here's a more technical explanation for those interested.)

Now, the oceans are not actually becoming acidic - they are technically becoming less basic. Current ocean pH is around 8.1. If CO2 emissions continue as they, the pH in 2100 is predicted to fall to 7.8.

7.8 doesn't sound so bad.

Well, it's not going to burn up half your face, turning you into an enemy of all that is right and good in Gotham City. But the trouble is that many of the critters with calcium carbonate parts have evolved to live in an ocean where there is a carbonate ion in every pot. They're not used to having to work for their carbonate. Not having enough carbonate ions around is stressful, and that's where the trouble starts. dissolving-in-acid kind of trouble?

Depends on the species. Some species seem to tolerate more acidic conditions just fine, while others die or have sad deformed little shells. Acidic water is especially hard on larvae. For example, when researchers grew larval oysters in pH 7.4 seawater, most of the baby oysters had incomplete or missing shells.

Corals actually do seem to dissolve in low-pH water. Researchers grew two species of hard coral in pH 7.3-7.6 seawater for a year. The corals' skeletons completely vanished, leaving the polyps living as strange naked anemone-creatures. (They were able to regenerate once back in normal seawater.)

But both of these experiments were relatively short-term, single species lab experiments. These can't account for changes in species interactions, like predation.

So what will the effects of ocean acidification be on reefs as an ecosystem?

The best prediction right now comes from researchers in Hawaii. They grew coral in giant tubs at today's CO2 levels and at the CO2 levels predicted for the year 2100. Their results had a little bit of good news and a lot of bad news.

The good news was that corals were still able to reproduce and grow in acidified water (albeit more slowly). But the bad news was that there was an 86% loss of crustose coralline algae. Crustose coralline algae is basically crunchy seaweed that grows a calcium carbonate shell. It's a critical part of the reef - it cements the reef together and provides a safe place for coral babies to grow.

So because most of the coralline algae disappeared in the "Year 2100" coral reef, it's time to worry. While coral species themselves might survive in a more acid ocean, the disappearance of crustose coralline algae would severely damage the coral reef ecosystem as a whole.

All your doom and gloom makes me grumpy. I like coral reefs and diving and poking at mantis shrimp!

Hey, poking at mantis shrimp is a hazardous occupation, but since I cut my diving eyeteeth digging around in holes for Maine lobster, I'm not one to judge. And did you know that mantis shrimp can see polarized light?

Seriously, as an coral reef lover, what can I do about ocean acidification?

Here's one hard way and two relatively easy ways. I'll give you the boring hard way first. The more greenhouse gases in the atmosphere, the more acidic the ocean will get. And of course other climate-related coral problems, like bleaching, will get worse. So - like you've heard 1,000,000,000,000 times before - support efforts to control emissions, and try to reduce your own emissions as much as possible.

But there's an easier action you can take to help keep coral reefs as healthy as possible. Make sure you're buying your critters and live rock from a reputable supplier! An overfished, cyanide-poisoned and dynamited reef will not have very much resistance to acidification (or bleaching or anything else, for that matter.) The Marine Aquarium Council certifies aquarium retailers and individual ornamental species as sustainable.

Another easy way to help coral reefs is to help local people make money off saving reefs, not destroying them. If you have some spare cash that you'd like to donate, I recommend the Coral Reef Alliance. They work with local communities and tour operators to develop sustainable businesses around protected, healthy reefs.

Expect to hear more about ocean acidification in the coming years. Dr. Jane Lubchenco, Obama's newly appointed head of NOAA, has identified ocean acidification as "the most insidious and pervasive threat to life in the oceans everywhere."

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