리딩그라피 레벨3 Reading 18 강 속에 이것이 없다면?

You might think of oysters as tasty seafood. But in New York City, they’re doing a great job for the environment too! Thanks to them, the Hudson River gets cleaner every day and is growing an underwater world.
New York City is helping oysters grow in the Hudson River. The city has put over 11 million young oysters in the river, and these small shellfish are making the water cleaner. But how does this work?
Oysters have a special way of cleaning up. They take in water, filter out harmful things, and leave them at the bottom of the river. As a result, the water becomes less polluted! In addition, oysters make *reefs or underwater homes. These oyster reefs provide places where lots of plants and animals can live. Because of the reefs, the ecosystem is getting healthier, and many sea animals have returned to the area.