Corals Grown in Labs Help Restore Critically Endangered Reefs

For the first time, researchers have successfully raised laboratory-bred colonies of a Caribbean coral species to sexual maturity. The hope, they say, is to restore and repopulate threatened reefs.

This revolutionary initiative was led by researchers from SECORE International - a leading conservation organization for the protection and restoration of coral reefs, the University of Amsterdam and the Carmabi Marine Research Station. 

"In 2011, offspring of the critically endangered elkhorn coral (Acropora palmata) were reared from gametes collected in the field and were out planted to a reef one year later," Valérie Chamberland, coral reef ecologist working for SECORE and Carmabi, explained in a news release. 

Elkhorn corals grow in a branching shape like elks' horns do, creating vast reef forests in shallow waters that protect shores from incoming storms and provide critical habitat for various organisms, including ecologically and economically important fish species. Repopulating degraded reefs and increasing habitat management has become increasingly important, as nearly 80 percent of all Caribbean corals have vanished in the last four decades. 

"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. This event marks the first ever successful rearing of a threatened Caribbean coral species to its reproductive age," Chamberland added in the release.

Following a rapid population decline, elkhorn corals were one of the first coral species to be listed as threatened under the U.S. Endangered Species Act in 2006. However, they were later listed as critically endangered under the International Union for Conservation of Nature's (IUCN) Red List of Threatened species in 2008.

Given its major decline and ecological importance, SECORE, Carmabi and partners from aquariums around the world have been working towards repopulating elkhorn coral reefs since 2010. Their project was designed to rear larger numbers of coral offspring, to be planted along degraded reefs throughout the Caribbean.

Generally speaking, elkhorn corals only reproduce once or twice a year, often within a few days following a full moon in August.

"We just learned that elkhorn corals can reach sexual maturity in only four years. This is exciting news, as we now know that offspring raised in the laboratory and out planted to a reef can contribute to the natural pool of gametes during the annual mass-spawning of elkhorn corals within four years," Chamberland added in the release. 

Their findings suggest these sexually-bred corals not only aid in the recovery of dwindling elkhorn coral populations by increasing the number of colonies, but also by increasing the reef's genetic diversity. 

"We don't get around to protect coral reefs and to apply additional management tools to reduce overfishing, pollution and other threats to coral reefs," researcher Dirk Petersen noted in SECORE's release. "So far, any restoration effort is restricted to small areas and involves costly and labor intensive hands-on work. We now need to take the next step forward to apply our findings on a larger scale in Curaçao and elsewhere in the Caribbean." 

Their findings were recently published in the journal Bulletin of Marine Science.

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