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Environment

Nursery-Bred Coral Show Promise — But We Need A Whole Lot More, Study Finds

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A. Neufeld
/
Coral Reef Restoration Foundation
A diver works in a reef nursery run by the Coral Reef Restoration Foundation.

Nursery-bred coral planted on reefs as part of a massive effort to save America’s only inshore tract do well initially, but most don’t survive beyond seven years.

The findings, published this week in the journal PLOS One, indicate what many scientists already know: reefs can’t be saved without fighting global warming.

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“In the absence of stressor mitigation, specifically related to global warming, practical restoration objectives must acknowledge that full and rapid recovery to historical baselines is not a realistic goal,” the study said.

Since the 1970s, the Caribbean has lost nearly 90 percent of staghorn coral, an important species for the reefs in the tropics. In the wild, they grow in thickets, creating dense branches that are good for fish and wildlife — and for building reefs.

Things got dire in 2014, when a new disease emerged, attacking mounding corals that help lay the reef's foundation. The disease, called stony coral disease, first appeared off Virginia Key and has now spread throughout the Caribbean. Fearful that the species might vanish, the National Oceanic and Atmospheric Administration launched an emergency rescue effort that included gathering species beyond the infected areas to preserve in labs and zoos. It also made restoration efforts even more urgent.

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Credit Pedro Portal / Miami Herald
The University of Miami Rosenstiel School of Marine and Atmospheric Science uses this model to show volunteers how to transplant staghorn coral.

Researchers say this study, funded by NOAA, the Nature Conservancy and a federal grant to Coral Reef Foundation, is the broadest look yet at replanting efforts in the Keys. The study examined 20 sites where more than 2,400 staghorn coral were replanted between 2007 and 2013. Led by Florida State University oceanographer Matthew Ware, researchers said that, up until now, too little time had passed to get a handle on long-term success of the staghorn bred in underwater nurseries.

 
During the first two years, researchers found the staghorn did well. They grew nearly four inches a year. After four years, a third had grown to 20 inches in diameter. But by five years, less than 35 percent survived. After seven years, 10 percent or less had survived. That rate of survival roughly matched wild populations, researchers said.

If rising temperatures and ocean acidification caused by global warming can be controlled, a plan created by NOAA estimates that it will take reefs about 400 years to recover.

To help save reefs in the meantime, scientists are studying reef DNA and working on developing more resilient coral in labs at places like the University of Miami.

But Ware and the paper’s researchers argue that lofty goal could take too long and be too expensive. 

“Coral practitioners need to be pragmatic about shorter-term approaches that might work to restore or help [staghorn] populations recover,” they write.

Increasing the number of coral transplanted — to better the odds of surviving— shows the most promise, they say.

An earlier version of this story incorrectly included lab-bred coral. The study only looked at coral raised in nurseries.