CORAL SPAWNING

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.

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.

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.

Rice corals only spawn once a year.

Spawning typically occurs between June and August, and shortly after a new moon.

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.

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.

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.