The Hudson River is infamous for being one of the most polluted rivers in America, but its waters have a lot more to them than meets the eye. Estuaries like the Hudson are some of the most biodiverse ecosystems in the world, where one can find marine, brackish and freshwater species intermingling in a relatively small area. In the Hudson River, oysters served as the foundation for this rich environment until around 1900, when a combination of overfishing and pollution locally decimated the stocks. Oysters begin their life cycle as small, mobile larvae. As they mature, they seek out a surface to settle on and develop their recognizable shells.