How do you keep New York’s harbor clean? At a high school on Governor’s Island just south of Manhattan, the answer has been tested: oysters. Marine biologists have used oysters for centuries for the efficient way they filter dirt out of water, as much as 50 gallons a day per oyster. In fact, there used to be trillions of oysters in the New York Harbor about 400 years ago before the water became too polluted for them to survive.

Thanks to the Clean Water Act, oysters can now populate the river and start slurping dirt once again. The only problem is how to get them back there. This week Change Reaction visited the New York Harbor School, a small public high