Well one of the first changes it the tadpoles start growing legs. Then it will continue to grow, changing and changing as it goes. Then it will start to live on land, and it will live on land as a tiny frog until it is completely grown up.
Tadpoles have fins, gills, and a two-chambered heart, similar to fish. As tadpoles grow up, they develop legs, lungs, and a three-chambered heart. The tail is reduced in size and lost completely as they prepare to leave the water.
It would be a form of pollution due to the runoff of chemicals which harm the marine life while helping with the growth of algea more suitably known as