Many people think that there is a problem with sea urchins on coral reefs. This belief stems from two sources. One is the fact that coral is comprised of two organisms, and one is algae which sea urchins eat. The other reason stems from press in the 1970s and 1980s that corals were overpopulating the reefs in the Caribbean and causing troubles for tourists visiting the reefs. Both beliefs are mistaken!
For starters the algae and sea weed that the urchins eat is not the stuff that helps the coral, but competitors that if allowed unchecked would over run the coral and destroy the reef. Without the sea urchins, they have found that the coral dies quickly, and so there are currently efforts under way to reseed the reefs with coral polyps and sea urchins by the University of Miami. According to this report, Dr Tom Capo has managed to mass produce them and will be releasing the juvenile sea urchins in the Florida Keys National Marine Sanctuary. This would not be tried if sea urchins were harming the coral reefs.
So what about them overpopulating the reefs in the 1970s and 1980s? There was a reported density of over 80 urchins per square meter on some reefs near St. John’s Virgin Island. The urchins got out of control and the reefs were suffering, and dying. Ironically enough, contrary to popular belief, it wasn’t the sea urchins that caused the problem, they were indicators of several problems.
Agricultural pesticides had killed off many of their predators while at the same time run off carried fertilizers that increased bad algae growth. The combination resulted in a rapid production of algae which started to kill the coral and the sea urchin numbers shot up because of increased food combined with decreased predation. People saw the coral dying and lots of sea urchins, so blamed one upon the other. It was a natural mistake to make!
People also don’t like sea urchins. The term urchin can mean dirty and grimy when applied to children. This is because they are small, thorny and inconvenience tourist when they go out to touch the reefs. People need to be educated that the coral reef is a complex system and every organism has a place, and that includes sea urchins! The Environmental Protection Agency now has a website that is trying to show the importance of all the interactions on the coral reefs. To learn more about sea urchins, you might also check out the Tree of Life website!
Sea urchins are not a problem to coral reefs, they are a valuable part of the coral reefs!
