6 fascinating facts about coral reefs

October 26, 2017, 10:37 a.m.
coral reef
Photo: Allan Hopkins/MNN Flickr Group

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. However, they 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. They eat microplastics, and they like them. A new 2017 study finds that corals, like fish, mistake plastic found in the ocean for prey and ingest it. The surprising part, however, is that researchers found they also like the taste. The scientists collected corals off the North Carolina coast and fed them a variety of options, which included sand and tiny bits of plastic. The corals overwhelmingly preferred the plastic.

“Corals in our experiments ate all types of plastics but preferred unfouled microplastics by a threefold difference over microplastics covered in bacteria,” Austin Allen, a PhD student at Duke University’s Nicholas School of the Environment, said in a statement. “This suggests the plastic itself contains something that makes it tasty.”

4. Coral reefs 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.

5. 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."

6. 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.

Editor's note: This story has been updated since it was originally published in August 2014.

Related on MNN: Can ocean plastic end up in seafood?