Coral Reef Biodiversity
Quick Fact
Coral reefs support around 25% of all marine species despite covering less than 1% of the ocean floor.
About This Species
Coral reefs cover less than 1% of the ocean floor yet support approximately 25% of all marine species. They are built by tiny coral polyps — animals related to jellyfish — that secrete calcium carbonate skeletons over thousands of years. Coral reefs provide food, shelter, and breeding grounds for an extraordinary diversity of fish, invertebrates, and other marine life. They also protect coastlines from wave erosion and support the livelihoods of hundreds of millions of people worldwide.
Why It Matters
Coral reefs are among the most threatened ecosystems on Earth. Rising ocean temperatures cause coral bleaching. Without urgent action on climate change, the majority of the world's coral reefs could be lost within decades.
Transcript
Coral reefs cover less than one percent of the ocean floor. Yet they support around a quarter of all marine species on Earth. That statistic never gets less astonishing to me, no matter how many times I say it. A healthy coral reef is one of the most complex and productive ecosystems on the planet — more biodiverse per square metre than a tropical rainforest. Every surface is occupied. Every niche is filled. Fish, invertebrates, algae, sponges, worms — all competing, cooperating, predating, and sheltering in an intricate web of relationships built up over thousands of years. But coral reefs are not rock. They're alive. Coral is an animal — a tiny polyp, related to jellyfish, that secretes a calcium carbonate skeleton. Inside each polyp lives a microscopic algae called zooxanthellae, which photosynthesises and provides the coral with up to 90% of its energy. That's why coral reefs only exist in clear, shallow, sunlit water. When the ocean warms, the coral expels its zooxanthellae. The coral turns white — bleached. Without its algae, it starves. If the heat stress continues, it dies. We've lost around 50% of the world's coral reefs in the last 30 years. The Great Barrier Reef has experienced five mass bleaching events since 2016. Coral reefs are the ocean's early warning system. What's happening to them is happening to the entire ocean. We are running out of time to act.