Lake Balaton, a big lake in Central Europe, got really dirty from the 1960s to the 1990s because of too much phosphorus from people. But then they cleaned it up, and now it's getting better. Scientists looked at the plants and animals in the lake from 2001 to 2017. They found that when there were just a little bit of plants in the water, the animals also decreased. But when there were very few plants, the animals didn't decrease as much because the small plants they eat didn't go away as fast. So, cleaning up the lake helped the water quality and the animals that live there.