The Sanctuary contains three separate coral reefs; the West Flower Gardens Bank, covering roughly 100 acres, East Flower Gardens Bank, at 250 acres, and Stetson Bank. The East and West Banks contain some 21 species of coral growing between 60 and 100 feet beneath the surface atop salt domes on the floor of the Gulf of Mexico, 100 miles from shore and surrounded by water up to 450 feet deep. Stetson, 30 miles closer to shore, is a 1,500-foot long ridge of pinnacles covered in fire coral and sponges.
Mass Spawning of Coral, Other Species
The mass spawning, or simultaneous release of eggs and sperm into the water column, occurs between seven and ten days after the full moon each August. Each species spawns within a unique window of time, then shuts down, and a short time later, another species begins to spawn. This activity fills the water with clouds of eggs and sperm, attracting a wide variety of marine life that feeds on it. Other species, including fish, brittle stars, sponges, and Christmas tree worms, spawn at the same time. This synchronization may provide protection from predation via safety in numbers; there is simply so much in the water at once that predators can’t possibly eat it all.
The 2009 mass coral spawning is expected to occur between August 11 and 14.
Triggers for Coral Spawning
Scientists believe three factors trigger the spawning: water temperature, phase of the moon, and time of sunset. The water temperature in August or early September seems to be conducive to the spawning, although scientists don’t know how coral can sense that water temperature. For that matter, they don’t know how coral know the phase of the moon, although the day of the spawning is clearly related to that as well.
Eggs and sperm have a limited life span, and so a species must release both within the same time period for fertilization to happen, says Peter Vize, PhD, professor of biological sciences at University of Calgary, Canada and lead author of a research paper on the Flower Gardens spawning event, Light sensing and the coordination of coral broadcast spawning behavior. Proc. 11th ICRS. in press, by Vize, P.D., Hilton, J.D, Brady A.K. and Davies, S.W. (2008).
This is especially true here, where deep water far from shore creates a diluting effect, and currents and waves can quickly carry off floating material. "If a coral spawns more than half an hour off from its reef-mates, it won’t have much chance of reproducing," says Vize. Mass spawns also occurs on coral reefs throughout the Caribbean and on Australia’s Great Barrier Reef.
Visiting the Flower Gardens Reefs
Live-aboard dive boats offer trips to the Flower Gardens out of Freeport, near Houston, and Lake Charles, Louisiana. Links to these providers can be found on the Sanctuary website. Due to the distance from shore, currents, waves, and other conditions, the Flower Gardens should be considered an advanced dive and not for beginners.
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