Coral species bred in laboratory reproduce in the wild

New York: Scientists have been successful in aiding a sustainable restoration of Caribbean reefs with the rearing of a threatened Caribbean coral species to its reproductive age.

A team of researchers from SECORE International -- a leading conservation organization for the protection and restoration of coral reefs -- has for the first time successfully raised laboratory-bred colonies of a critically endangered elkhorn coral (Acropora palmata) to sexual maturity.

A new technique was developed whereby male and female gametes were caught in the wild and fertilised in the laboratory to raise larger numbers of genetically unique corals, the study said.

The method promoted the formation of new genotypes that could potentially cope better with the conditions on modern reefs than their already struggling parents, the study showed. 

These sexually-bred corals, therefore, not only aid in the recovery of dwindling elkhorn coral populations by increasing the number of colonies, but also by increasing the genetic diversity of this critically endangered species, thus giving evolution the opportunity to play its part, explained the researchers.

In 2011, the offsprings of the endangered elkhorn coral were reared from gametes collected in the field and were outplanted to a reef one year later, the researchers revealed.

"In four years, these branching corals have grown to a size of a soccer ball and reproduced, simultaneously with their natural population, in September 2015,” said Valérie Chamberland, coral reef ecologist from Carmabi Marine Research Station in Curaçao, a Dutch Caribbean island.

Elkhorn corals reproduce only once or twice a year, generally a few days after the full moon in August. During these nights, the Acropora colonies synchronously release their gametes into the water column, the findings, published in the journal Bulletin of Marine Science, showed.

The researchers collected small proportion of these gametes, and produced the coral embryos by in-vitro fertilisation, mixing sperm and eggs in the laboratory. 

The coral embryos then developed into swimming larvae within days and eventually settled onto specifically-designed substrates. After a short nursery period, the scientists outplanted these substrates with the newly-settled corals in the reef. 

An estimated 80 percent of all Caribbean corals disappeared over the last four decades and the elkhorn coral was one of the species whose decline was so severe that it was one of the first coral species to be listed as threatened under the US Endangered Species act in 2006 and as critically endangered under the IUCN Red List of Threatened species in 2008.