In order to study ocean acidification in the field, scientists from five European countries built ten mesocosms—essentially giant test tubes 60-feet deep that hold almost 15,000 gallons of water—and placed them in the Swedish Gullmar Fjord. After letting plankton and other tiny organisms drift or swim in, the researchers sealed the test tubes and decreased the pH to 7.8, the expected acidity for 2100, in half of them. Now they are waiting to see how the organisms will react, and whether they're able to adapt. If this experiment, one of the first of its kind, is successful, it can be repeated in different ocean areas around the world.