Researchers of SECORE International (USA, Germany), the University of Amsterdam (Netherlands) and the Carmabi Marine¹ Research Station (Curaçao) have for the first time successfully raised laboratory-bred colonies of a threatened Caribbean coral species to sexual maturity². These findings have been published in the latest issue of the scientific journal Bulletin of Marine Science. "In 2011, offspring of the critically endangered elkhorn coral (Acropora palmata) were reared from gametes collected in the field and were outplanted to a reef one year later", explains Valérie Chamberland, coral reef ecologist working for SECORE and Carmabi. "In four years, these branching corals have grown to a size of a soccer ball and reproduced, simultaneously³ with their natural population, in September 2015. This event marks the first ever successful rearing of a threatened Caribbean coral species to its reproductive age." 

 

Due to its large size and branching shape, elkhorn corals created vast forests in shallow reef waters that protect shores from incoming storms and provide a critical habitat for a myriad⁴ of other reef organisms, including ecologically and economically important fish species. An estimated 80% of all Caribbean corals have disappeared over the last four decades and repopulating degraded reefs has since become a management priority throughout the Caribbean region. 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 U.S. Endangered Species act in 2006, and as critically endangered under the IUCN Red List of Threatened species in 2008. Consequently, measures to aid Caribbean reef recovery often focus on the elkhorn coral given its major decline and its ecological⁵ importance. 

 

Since 2010, SECORE, Carmabi, and partners from aquariums⁶ around the world started a project aimed at developing techniques to rear larger numbers of elkhorn coral offspring so they could eventually be outplanted to degraded reefs throughout the Caribbean. "Our approach differs substantially from the one generally used by the large number of reef restoration groups that operate throughout the Caribbean", explains Dirk Petersen, coral reef expert and director of SECORE. "These groups generally use the 'coral gardening' approach, where small fragments are harvested from coral colonies on the reef. The fragments are then grown in special nurseries to larger sizes before they are returned to the reef." Although this method has been applied⁷ throughout the Caribbean, it does not allow for new genetic⁸ combinations as the fragments harbor the same genes⁹ as the donor¹⁰ colonies and are therefore copies of their parents. "By contrast, SECORE developed a technique whereby male and female gametes are caught in the wild and fertilized¹¹ in the laboratory to raise larger numbers of genetically¹² unique corals", says Dirk Petersen.

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