Scientists theorized that all ecosystems need sunlight as an energy source. What has been discovered on the ocean floor that has challenged this theory

It has been discovered that many animals make their own light, called bioluminescence, to communicate, find mates, scare predators, or attract prey in deep ocean floor. Most animals cope with this by being very small and needing less to eat or by growing very slowly. they also feed on plankton and other animal waste that falls down from upper ocean.