Environment Planet Earth 6 Fascinating Facts About Coral Reefs By Jaymi Heimbuch Jaymi Heimbuch Twitter Writer California Polytechnic State University, San Luis Obispo Jaymi Heimbuch is a writer and photographer specializing in wildlife conservation. She is the author of The Ethiopian Wolf: Hope at the Edge of Extinction. Learn about our editorial process Updated May 13, 2020 Photo: Allan Hopkins [CC by NC-ND-2.0]/ MNN Photo Pool Share Twitter Pinterest Email Environment Weather Outdoors Conservation Blue-cheeked butterflyfish cruise a colorful reef Coral reefs are one of the world's most colorful and diverse ecosystems, and though they cover only about 1 percent of the ocean floor, they have a huge effect on the health of the rest of the world. Healthy coral reefs mean healthy oceans which means healthy planet. Here are five fascinating facts about these amazing ecosystems. 1. Corals are not plants. They're actually animals and are are, amazingly enough, relatives of jellyfish and anemones. 2. Though corals are animals, they do rely on photosynthesis to survive. But the coral polyps aren't doing the actual photosynthesizing. Microscopic algae, or zooxanthellae, live within the cells lining the digestive cavity of the polyp. As much as 90 percent of the energy a polyp needs comes from this symbiotic relationship. The other 10 percent comes from hunting the polyp does by extending its tentacles to catch prey. 3. Reefs formed by corals are one of the most biodiverse marine areas on the planet, housing hundreds and even thousands of species. The diversity is due to the fact that reefs are an important location for finding food, shelter, mates and places to reproduce. Reefs also act as nurseries for large fish species, keeping them safe until they are large enough to strike out into the deeper ocean. 4. Coral reefs are important to the development of new medicines. According to NOAA, "Coral reef plants and animals are important sources of new medicines being developed to treat cancer, arthritis, human bacterial infections, Alzheimer’s disease, heart disease, viruses, and other diseases." 5. Coral reefs are so valuable to the fishing and tourism industries, as well as protecting shorelines from storm damage, that destroying just 1 kilometer of coral reef means the loss of between $137,000 to $1,200,000 over a 25-year period, according to the World Resources Institute. And yet, nearly 60 percent of the world's coral reefs are threatened by human activity.