September 16, 2009
ATM blogger Megan Gambino spent a week in Panama reporting on research taking place at two locations—Barro Colorado Island and Bocas del Toro—of the Smithsonian Tropical Research Institute (STRI). Read on in this final dispatch to follow her day-to-day adventures.
Day 5 and Day 6: Coral Spawning!
By day five of my Panama trip, after a night of watching bats forage at Barro Colorado Island and two nights of diving near Bocas del Toro, I was beginning to think I was going to get a moon burn.
Only a couple of young corals “still learning the ropes,” according to coral reef biologist Nancy Knowlton, spawned on the second night dive. By the next day, the suspense was building. (Better, I thought, for the story I’ll write for the magazine!) At lunch, Nancy jokingly hit her fist on the table and said, defiantly, “It will happen.”
As the day went on, the jokes got worse. Barry “Oh Baby” White was suggested as mood music. Kylee Pawluk, one of the research assistants, suggested that before the dive we all eat aphrodisiacs, such as oysters and strawberries, to spawn the spawning. And coral reef expert Don Levitan sported his lucky red swim trunks. He asked if anyone had cigarettes for post-dive.
That night, a few more people joined the dive team patrolling the reef, as well as a camera crew that wanted to catch the spawning on video. Around 7:25, just as everyone began putting on their wetsuits, sea worms called palolo worms began spawning around the boat. The worms break in half and the tail section, containing reproductive cells, swims to the surface and releases eggs and sperm in a cloud of bioluminescence. According to the scientists, the worms’ spawning was a precursor to what the coral would soon do.
“This is it,” said Nancy. “Everybody’s in the mood for sex.”
Sure enough, at 8, just as the scientists predicted, M. franksi, the species of coral in the deeper section of the study site, began setting (fyi: that’s when the gamete bundles reach the surface of the coral, making it look pimply). The divers placed red glow sticks on setting corals, and the sea floor began to look, as Nancy had described, like “a garden of red tulips.”
Like clockwork, the coral colonies started spawning around 8:20, one triggering another triggering another. Only a couple of the late-spawning species, M. annularis and M. faveolata, spawned that night. The majority of those would spawn the next night, and as a snorkeler, I was in a better position to witness them since they are generally found in shallower water. I swam down to a large colony and watched as its gamete bundles, about two millimeters in diameter, lifted in unison.
It felt like I was in a snow globe, or maybe bubble tea. The bundles, made up of about 100 eggs and one million sperm, slowly drifted upward, where they broke apart. I laid there among millions of tiny eggs covering the surface of the water.
Later that night, Nancy and Don explained how zygotes would form on the surface and then drift down current for about five days before settling on the bottom. Coral colonies typically grow a centimeter per year, and given that the population of the coral in the area is pretty stable, the researchers estimate that only about two coral babies from every large, 500 to 1,000-year-old coral survive. (Basically, each coral colony produces a replacement just one or two offspring for when it dies.)
“To me, coral spawning is like an eclipse of the sun,” said Nancy. “You should see it once in your life.”
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