Wolves change the flow of rivers. Starfish decimate coral reefs. But algae, they nearly destroyed all life on earth by polluting the entire planet with deadly

Wolves change the flow of rivers. Starfish decimate coral reefs. But algae, they nearly destroyed all life on earth by polluting the entire planet with deadly oxygen, caused all the exposed iron (an essential nutrient) to oxidize/rust and triggered a global ice age and mass extinction. We've got nothing on algae.