The Annual Coral Spawning Event
Join us for a celebration of one of nature’s most spectacular marine events—coral spawning!
One night a year, when the lunar phase and the water temperature are just right, all rice corals (Montipora capitata) across the reef ecosystem simultaneously release eggs and sperm. The abundance of these gametes swirling around in the water column resembles a snow flurry.
Beautiful and awe-inspiring to witness, this singular event is an essential part of the reef’s life cycle. Fish and invertebrates feed on the drifting gametes. Surviving larvae form new coral colonies. The resulting reefs provide shelter for juvenile and adult fishes, and the cycle of life continues.
Coral Spawning FAQs
Corals are tiny living animals that eat, grow, and reproduce. They have a symbiotic relationship with their primary food source — small photosynthetic algae called zooxanthellae.
Rice coral (Montipora capitata) is a common coral in Hawaiʻi and may form as plates or spires, depending on the depth and calmness of the water around it. Rice coral gets its name from the rice-like texture of its surface.
Coral is an animal, but reproduction poses a unique challenge because they cannot move about to find a mate. To overcome this barrier, on one night each year, rice coral polyps simultaneously release a barrage of gametes (bundles of egg and sperm) into the water column forming planula, or larvae. This synchronistic event is crucial to the survival of the corals — there's power in numbers, and surely some are bound to survive.
While we still don’t fully understand what triggers the spawn, we do know that it’s essential for the survival of these corals, and in effect, the entire coral reef ecosystem. The gametes and planulae provide nutrition for the many fish and invertebrates, and the formation of new reefs provides shelter for juvenile and adult fishes.
Spawning typically occurs between June and August, and shortly after a new moon.
The Kumulipo, or Hawaiian creation chant, states that life began with the coral polyp, and as more life was born, it became more and more complex. The historical and cultural significance of ko‘a, or coral, cannot be understated. It is no wonder that corals continue to amaze us to this day.
Unfortunately, corals face challenges as ocean temperatures rise. Coral bleaching and ocean acidification threaten the very foundation of the reef ecosystem. Coral bleaching occurs when temperatures increase to beyond the safe temperature threshold, which causes the coral polyps to respond by ejecting their primary food source — small photosynthetic algae called zooxanthellae. This loss of appetite causes the corals to slowly die over one to two weeks. In September 2015, ocean water temperatures reached sustained levels that catalyzed unprecedented coral bleaching worldwide. Hawaiʻi’s corals experienced up to a 50% mortality rate in some areas.
Ocean acidification is the effect of increased carbon absorption into the ocean. As acidity increases, coral and other shell-forming animals find it difficult to build shells. Scientists have also discovered that chemical-based sunscreens can have very damaging effects on corals.