By: Jacqueline Bonfiglio

Although we are approaching the end of the summer, this upcoming month is a very exciting time here at Coral Restoration Foundation. During mid-August, around the full moon, the Florida Keys Coral Reef Tract will undergo its annual synchronized spawning. This is an event which occurs only once a year within a very short time frame. However, it is vital to the corals because it allows them to sexually reproduce. The annual coral spawning is vital to the health and growth of coral reef systems because it enables the sharing of the coral’s genetic material, which in turn promotes the biodiversity of corals.

Typically, most coral reef systems only have one short spawning period. However, in specific regions such as within Kenya, some coral reef tracts have spawning periods that last for up to seven months. Why is this? Scientists don’t have a complete understanding of synchronized coral spawning, but they have developed several hypotheses as to what determines the duration of spawning periods and when they happen. One hypothesis deals with the duration of wind over a reef system. If there is a long windy season then corals should have a short spawning period, in contrast to regions which have a shorter windy season. This aligns with the differences between the Caribbean and Kenyan reef tract. As the locals are well aware, the Florida Keys has a prolonged windy season. In Kenya, they have a short windy season which could explain why their coral reef tract has a seven-month spawning period [1]. Another hypothesis deals with synchronized coral spawning set by the solar cycle rather than the coral’s biological clock. In this study, scientists tested three coral fragments from the same colony and simulated the sunset on the same day of predicted spawning at zero, one, and two hours earlier than the sunset. The results indicated that coral spawning was not initiated by a biological clock, but directly from local solar cycles [2]. This study explains why coral spawning is often predicted based on the lunar cycles and when the full moon occurs.

These are only two of many studies that have been conducted on the spawning of coral reef systems. It is evident that there is still much we can learn from this phenomenal annual occurrence. Since it is challenging to predict the exact day and time of coral reef spawning, it is important for Coral Restoration Foundation and teams preforming research on this event to be prepared for the occurrence to happen in the weeks around the full moon period. It is only from studying this rare event that we will gain more insight on the questions and hypothesis that are still unknown. We look forward to sharing what we’ve studied and learned from this year’s upcoming coral spawning in the Florida Keys Coral Reef Tract in our next month’s newsletter!



[2] Brady, A. K., J. D. Hilton, and P. D. Vize. “Coral Reefs.” Coral Spawn Timing Is a Direct Response to Solar Light Cycles and Is Not an Entrained Circadian Response 28 (2009): 677-80. Web.

Broad, William J. “In Secrets of Coral Spawning, Hope for Endangered Reefs.” The New York Times. The New York Times, 2016. Web. 24 July 2016.

[1] Woesik, R. Van. “Proceedings of the Royal Society.” Calm before the Spawn: Global Coral Spawning Patterns Are Explained by Regional Wind Fields 277 (2009): 715-22. Web.