I have heard so much about this and watched a great program on Planet Earth- the Deep seas from Discovery which peaked my interest. I have heard divers say it looks like an underwater snowstorm.
No one really understands what factors contribute to triggering a spawning event or how corals synchronize to spawn all at the same time. Moon phase is undoubtedly an important influence because spawning events can be effectively predicted from closely observing the various phases of the moon. It will generally happens about eight days after August’s full moon.
- In 2010 in the Caymans the full moon was Aug 24th and spawning was seen Aug 29th-31st. This year the full moon is on Sept 12th in the Caymans and spawning is predicted to be seen Sept 16-18th. For 2012 the full moon is set for Aug 31st and anticipated spawning in Caymans is Sept 5-7th. In Bonaire, which is an excellent place to witness coral spawning due to the proximity of the reefs from the shore, and abundance of coral species, spawning takes place in September and/or October. In the Caribbean, coral spawning occurs usually in the first week of August. I am still researching Florida but it appears to have been last week in Key Largo according to Amy’s Amoray Dive Resort. They went out 4 nights and saw spawning all 4 nights. Darn it, day late and dollar short!
The generally accepted schedule is for branching corals like finger, staghorn and elkhorn corals in the Keys to spawn is three to five days after the full moon, about two hours after sunset. Star and boulder corals spawn six to eight days after the August full moon, about three hours after sunset.
Anyway, the coral spawning almost always happens at night a few hours after sunset and just after the water has reached its warmest temperature of the year. Scientists also believe that water temperature, tidal fluctuations, and length of the daylight period may contribute to corals spawning on cue. It is called broadcast spawning and it enables the coral which can’t move to get to each other, the ability to send sperm and eggs adrift in the water in massive quantities and over immense distances. When egg and sperm unite they create a larval-stage “planula” which swims to the surface to drift in the current and grow. Somewhere between two days and two months the planula settles to the bottom where it grows into a polyp. The polyp grows into a coral head by asexual budding that creates new polyps.
Why do it this way? Well, it is to increase the chances of fertilization. It also makes it difficult for their predators to scoop up all of the eggs. Imagine all the turtles, nursesharks and fish that are out in the evening fishing!
Divers hoping to witness spawning should choose a dive site that has plenty of coral, and relatively shallow to maximize your bottom time. Look carefully at the coral for swollen polyps with little pink eggs inside them as this is a sign that they are ready to spawn. Usually a few hours after sunset is the best time to spot coral spawning.
I can’t wait to see this happen!