A newly discovered coral reef off the Australian coast is 500 meters tall, Canadian Broadcasting Corporation reported. It is the largest detached reef to be discovered in 120 years and it is over 1.5 kilometers wide. But what are coral reefs made of?
According to Canadian Broadcasting Corporation, an exciting oceanic discovery has been made near Australia. “Australian scientists found a detached coral reef on the Great Barrier Reef that exceeds the height of the Empire State Building and the Eiffel Tower,” the article said. “The ‘blade-like’ reef is nearly 500 meters tall and 1.5 kilometers wide. The reef lies about 40 meters below the ocean surface and and about 6 kilometers from the edge of Great Barrier Reef.”
Coral reefs are an odd phenomenon in the ocean. They require symbiotic relationships between multiple species in order to survive.
The Living Coral
Coral reefs have the appearance of a rock outcropping or stalagmites jutting up from the ocean floor, but their existence is far more active.
“These are animals that actually farm or host photosynthesizing single-celled algae within their bodies,” said Dr. Harold J. Tobin, Professor in the Department of Earth and Space Sciences and Director of the Pacific Northwest Seismic Network at the University of Washington in Seattle. “The corals are another incredibly complex environment where there are interactions between a number of different organisms to keep the entire reef healthy.”
Dr. Tobin said that at first glance, the coral may not appear to be an animal. However, it is, rather than some kind of plant. He said it’s a cnidarians related to both anemones and jellyfish, complete with stinging cells. Coral polyps open up and wave in water to waft zooplankton or entice them—or fish—in. The coral then sting them with nematocysts and pull them in to eat and digest them.
That’s only a small part of the life of coral.
“Most corals are colonies of individual polyps [and] each polyp is actually a separate animal,” Dr. Tobin said. “A coral head is a colony of many thousands of those individual animals. Ultimately, those corals, if they build up reefs, we call them a particular type of coral which is a hermatypic. They build up a herm or a big, massive structure so they’re hermatypic reef-building coral animals.”
Dr. Tobin said that the success of corals depends on a symbiotic relationship. Coral polyps can be carnivorous, eating small things that drift their way and that they can trap, such as floating plankton or small fish. At the same time, he said, they host microscopic dinoflagellates that are called zooxanthellae, which are the photosynthetic algae he mentioned.
“They essentially farm them,” he said. “The dinoflagellates live in the coral. They’re protected by the polyp, and the internal structures of the polyp, from the surrounding wave motion and things like that. [The dinoflagellates] can effectively photosynthesize; their food is then basically diffused into the coral polyp itself, feeding the polyp. The corals actually digest some of the zooxanthellae they’re hosting, but not enough to destroy the colony.”
Dr. Tobin said this is why corals have to receive sunlight—the zooxanthellae have to photosynthesize and the corals open up during the daytime. Then at night, they digest whatever was captured during the day.
These symbiotic relationships of the organisms that live within a coral reef are the backbone to the complex living structure of the biodiverse environment of the coral reef.
Dr. Harold J. Tobin contributed to this article. Dr. Tobin is Professor in the Department of Earth and Space Sciences and Director of the Pacific Northwest Seismic Network at the University of Washington in Seattle. He earned his BS in Geology and Geophysics from Yale University and his PhD in Earth Sciences from the University of California, Santa Cruz.