Coral Spawning by Moonlight

Coral Spawning by Moonlight:
The Golden Gametes of Curacao

Text and Photography by Tom and Therisa Stack

Smiling at me from across the table, a sparkle in her eyes, Therisa asked, “Ready to see how corals do it?” She was referring to the ever elusive coral spawn, a mating ritual like no other. The sun was already setting over an expectant ocean. Our cameras were loaded, our strobes fully charged and ready. The real excitement was already brewing in the soon to be coal dark depths of the sea. The corals would shortly create a primordial broth of eggs and sperm, thus birthing new life in the womb of the ocean as they have done for eons.

For several days after the September full moon, corals had been preparing to spawn in the pristine waters off Curacao. Our attempt to record the event in August off the Florida Keys was thwarted by stormy weather. When marine biologist Nico Engelmann, consultant for Habitat Curacao, explained that the event occurred a month later in the Netherlands Antilles, we immediately booked a flight in another attempt to photograph this astounding spectacle.

Nico explained that corals need to be at least ten years old to reproduce. Once of age, spawning can be done in several ways. Some are broadcast spawners, releasing both eggs and sperm bundled together in single spherical gametes. The outer membrane of the gamete will dissolve in a few hours, allowing fertilization to take place in the water. Other corals are hermaphroditic and fertilize eggs within the polyp’s gastrovascular cavity. Even others simply bud new polyps.

Under the control of the lunar cycle, water temperature and the duration of daylight (photo periodism) the release of eggs and sperm is a nonsynchronous event of astounding proportions. We were after the larger broadcast reproductive release actions of Star Corals.

Scientists are still in the process of learning about coral reproduction; much is unknown and yet to be discovered. As the bow of the dive boat knifed through black waters, Nico confirmed what we already knew. Star Corals usually spawn between 10:00 and 10:30 pm. The operative word here was “usually!” Since we didn’t want to miss our window of opportunity, we decided to enter the water at 8:30 pm, especially since some other species would probably be spawning earlier.

The dive boat swayed ever so slightly in calm waters as we geared up in anticipation of yet another secret event we hoped the sea was about to reveal to us. Shimmers of bioluminescence radiated from us on the surface as cameras were lowered into our outstretched hands. Our pencil beams of light illuminated the giant stands of Star Corals. We located a sandy bottom between two promising coral heads and settled in like midwives for our long wait.

“WHOoooo! WHOoooo!” was Therisa’s way of directing me to look where she pointed at flower-like polyps. Pictures were taken at the beginning for luck, then we waited. The minutes ticked by slowly. An occasionaal squid or fish was our only company as we stood like sentinels in the dark. A hush fell between us, the only sound was our slow, even breathing. We shifted from one fin to the other. The wait continued. We couldn’t have been more involved with the birthing process if the birth was our own new arrival. And still the wait continued-one hour, one and a half hours. Our lower backs ached with a dull pain from standing at attention for so long. Then we realized we were down to a few hundred pounds of air. I signaled Therisa to surface. She kicked and stomped her fins while emphatically shaking her head “No!” and pointing to the gametes in the mouth of each polyp. Safety first, I signaled again and we began our slow, dejected ascent to the surface.

I knew what she was feeling, we had waited so long for the promised gift of life. To miss it now seemed a shame.

Climbing onto the dive platform we were whining about our poor luck when Nico surfaced behind us shouting, “It’s happening!”

Knowing the coral would be spent in a matter of minutes we hurriedly strapped on fresh tanks and returned to the arms of the sea. Golden gametes surrounded us as the polyps infused the ocean with their mixed seed. We excitedly followed the gametes to their source and watched in awe and amazement, almost too stunned by the beauty of it all to remember to take pictures. Focus, shoot and wait for the strobe to recycle-concentrate, we had to remind ourselves again and again!

Brittlestars emerged to feed on the spawn. In a few short minutes it was over as fast as it had begun. We surfaced in jubilation, knowing we were privileged to have witnessed an event full of hope for the future of the world’s oceans.