By Caroline Catherman
Medill Reports

For years, Atlantis fanatics have zealously searched for a city on the ocean floor.

But there’s been a thriving metropolis hiding under the ocean’s currents for millions of years. These constantly expanding reefs have the most biodiversity — the number of living species in one place — of any ecosystem on our planet. They hold up the entire marine food chain, harboring 25% of ocean species, according to the National Oceanic and Atmospheric Administration.

Maybe you’ve heard that the majority of the reefs have “bleached,” and written them off as a lost cause. But coral reefs are actually one victim of human activity that can be viewed with hope. Unlike most damage, bleaching is reversible — if we act fast to save coral. Learn more about what bleaching is and how we can help coral through the video below.

https://vimeo.com/532036367

Caroline Catherman is a health, environment, and science reporter at Medill. You can follow her on Twitter at @CECatherman.