Can an army of Caribbean king crabs help save Florida’s coral reefs? Some scientists are betting on it. Coral reefs are living organisms that serve as an essential food source and habitat for many marine creatures. But in recent years, many of the world’s corals—including 90 percent of those in Florida—have been damaged by climate change, pollution, and other threats. Algae are a big problem too: The plants—which thrive on nitrogen and other byproducts of aquatic and human waste—blanket the coral and stunt their growth. Caribbean king crabs, however, eat a massive amount of algae. A 2021 study found that reefs that scientists had filled with crabs had about 85 percent less algae after a year than reefs left alone. Now the scientists plan to drop hundreds of crabs into Florida’s seas, in hopes that the crabs will help the reefs fight back. Although ecologists already know how to grow and plant corals to replenish reefs, that hasn’t been enough on its own, notes Jason Spadaro, a marine ecologist who’s heading up the team. “Now,” he told Vox, “we need to help them survive.”