giving coral reefs a future

DLAB (D-lab)―how it is nicknamed by the researchers―does not only release its eggs and sperm during daytime just before sunset, it also spawns a few nights each month from spring to fall. This coral thus follows a different reproduction strategy than most of the other reef-building corals, which usually rendezvous for one to few nights once a year. Conveniently, when DLAB corals are getting ready to spawn, butterflyfish swarm around the colonies to get their share of a nutritious feast on coral eggs and sperm. This behavior is an excellent indicator for divers to spot which brain coral colonies are going to spawn next.

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Photos: left & mid, collecting grooved brain corals' spawn (Ashley Lindstrom); right, ~ one year old DLAB corals from an earlier cohort (SECORE) .

In mid-June, a team of CARMABI and SECORE scientists, supported by volunteers from THE DIVESHOP, were able to collect DLAB spawn on the reef. After letting the DLAB larvae settle on special substrates (SECORE's coral settlement substrates, aka tetrapods), they were put into an experimental set-up within one of our CRIBs (Coral Rearing In-situ Basins). Two specific conditions were tested by our local team of researchers.

“First, we offered food to the baby corals in the form of tiny crustacean larvae (freshly hatched Artemia nauplii) to enhance their growth, and second, we provided them with single-cell algae which they will hopefully have taken up to initiate their symbiotic relationship as early as possible”, explains Kelly Latijnhouwers, our Caribbean Restoration Coordinator on site.

“Based on a previous study on DLAB babies conducted here on Curaçao (see publication link below), it is known that by obtaining their algal symbionts early in life, just settled DLAB corals have much higher chances of survival,” says Valérie Chamberland, our Research Scientist on Curaçao. The symbiotic algae that live inside the corals contribute a great part to their nutrition and are thus vital to them.

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Photos: experiment on early life stage growth of the grooved brain coral. Left: this year's one week old DLAB coral polyps under the microscope with fluorescence light; mid & right: Kelly Latijnhouwers working at the experimental set-up within CRIB (all photos SECORE).

Two weeks ago, after both feeding and adding algae treatments were completed, all coral babies were transferred to the reef, and their survival rate will be monitored during the upcoming months. The results of this study will help to determine the best way to raise corals for sustainable reef restoration on larger scales. Life is hard for baby corals, and competition on the reef is intense. Therefore, it is essential to grow them under optimal conditions, giving them a head start before transferring them back into the wild.

In the meantime, the team on-site is already preparing for the next spawning event. “We will start monitoring the Acropora spawning on August 1st”, says Chamberland. This time, the team will have to look out for spawning corals during night dives. Stay tuned for more!

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Photo: grooved brain coral with butterflyfish feeding on its spawn (Ellen Muller).

Read more

About SECORE's work on Curaçao

Giving coral babies a head start by growing them with sea urchins

Learn more about corals and how they reproduce

Watch How to Grow Coral on Curaçao

Scientific publication: The reproductive biology and early life ecology of a common Caribbean brain coral, Diploria labyrinthiformis: Chamberland et al., 2017