VIRGIN ISLANDS (3 Aug 2004) -- Something about the few nights after the full moon every August puts corals near the Virgin Islands in the mood for reproduction. This week, scientists and biologists in the territory expect elkhorn, staghorn and star corals surrounding the territory to spawn, or release their sex cells into the water for possible fertilization. Coral spawning is usually an annual event that offers swimmers a rare opportunity to see coral reproduction. Corals, which spend the majority of their lives planted firmly on the ground, produce both sperm and egg cells. When the time comes for reproduction, they release both types of cells into the water around them. The cells move through the water in small, spherical bundles. When a coral egg is fertilized by a sperm cell, it becomes an organism that will swim until it finds a place to settle and mature into a full-grown coral. Coral spawning is a recently discovered phenomenon. Until the 1980s, scientists believed that coral reproduced passively, like plants. According to information posted on the Florida Keys National Marine Sanctuary Web site, scientists at Australia's Great Barrier Reef were the first to notice the behavior. In 1990, scientists at Flower Gardens National Marine Sanctuary observed a mass spawning shortly after sundown. Jeff Miller, a fisheries biologist on St. John, said that the timing of coral spawning around the Virgin Islands is difficult to predict. "It's not an exact science by any means," Miller said. "It's oriented around the full moons in August. With the full moon so late in July, the corals may spawn very soon. However, water temperatures also come into consideration." Caroline Rogers, a marine ecologist for the U.S. Geological Survey on St. John, said scientists have not discovered the precise reason for the timing of coral spawning. Scientists worldwide have postulated that tides, water temperature and light all contribute to coral reproduction. Predictions for coral spawning are often made with consideration of the timing of the full moon and the timing of the corals' spawning in previous years. Spawning is more difficult to predict in the Virgin Islands than places like the Great Barrier Reef, Rogers said. At the Great Barrier Reef, several corals and other animals that reproduce by spawning, like sea cucumbers, spawn at the same time. | | Spawning coral Rogers said she plans to dive and observe local spawning Tuesday night. When the coral spawns, a mass of little pink balls - bundles of sex cells - fill the water. In the Virgin Islands, there are several good places on each island to watch the coral spawn, Rogers said. Some places have only a few coral colonies, but there are hundreds in others. And reefs in the territory are relatively easy to get to, Rogers said. "We're lucky - you can swim and find them just off shore," she said. "There are other places that you have to take a boat out to the coral." SOURCE - Virgin Islands Daily News |
