Oh, the humanity: CO2 will allegedly cause Nemo to wander away from home; also, CO2 allegedly makes hermit crabs slower to withdraw into their shells when confronted by a toy octopus

Ocean Acidification Can Mess with a Fish's Mind: Scientific American

In more acidic waters clown fish wander too far from safety, sea snails fail to avoid prey
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Monterey, Calif.—Mental problems at sea? Fish and mollusks could begin to have them—thanks to rising CO2 levels. Some of the resulting behaviors are odd, some compromising, and they reveal just how fundamentally carbon emissions are affecting our increasingly fragile Earth.
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Small clown fish (yes, Nemo), for example, normally stay extremely close to the coral in which they spend their entire lives. But as the water becomes increasingly acidic—as in various recent experiments—they tend to wander farther and farther from home. This uncharacteristic "boldness" is not necessarily a good trait because the farther they swim, the more likely they are to get eaten by predators.   [Isn't that good news for the predators?]
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In experiments done at the Monterey Bay Aquarium Research Institute here, hermit crabs living in highly acidic conditions did not show the increased boldness of Munday's clown fish, but they took far longer to withdraw into their shells than normal when they came under attack from a potential predator (in this case, a toy octopus).