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Transplanted Bleaching-Resistant Coral Retain Their Resistance To Heat
(Credit: Hans Braxmeier from Pixabay)
NatureEnvironmentScienceSustainability

Transplanted Bleaching-Resistant Coral Retain Their Resistance To Heat

Katie Barott of the University of Pennsylvania’s School of Arts & Sciences led a study to see if climate-change resistant corals could grow on battered reefs after transplantation. Her team took corals that survived a severe bleaching event and transplanted them to a new reef where they retained their resilient qualities.

This is excellent news because the looming threat of the climate crisis, acidification, and warming oceans hangs heavy on the world’s coral reefs. Most of them are struggling to adapt to the increasingly inhospitable waters.

Scientists are concerned that corals will fall victim to global warming very soon because mass bleaching events occur more frequently. This new study’s findings offer hope that hardy corals could be the saviors, restoring ruined reefs in the future. Barott and colleagues believe this strategy can buy corals more time as the world battles climate change.

Coral bleaching occurs when the ocean warms to higher-than-normal temperatures, prompting corals to expel the algae they contain, which is their food source. Without sustenance, the coral turns white and eventually dies. The phenomenon has plagued Australia’s Great Barrier Reef and Hawaii’s reefs in recent years.

The researchers acquired their hardy corals from a reef in Hawaii that endured a severe bleaching event in 2015. They transplanted samples to two different locations, one with high water flow and another with still waters. They left the corals there for six months.

The team also took coral samples from each site and put them in tanks in a lab, simulating another bleaching event by increasing the water temperature over several days. They found that in all scenarios, the bleaching-resistant corals remained unaffected.

Katie Barott, who led the research team, said:

If you take a coral that is resistant to bleaching in its native habitat, it could be that the stress of moving to a new place might make them lose that ability.

 

The big thing that we were interested in here was trying to experimentally test whether you can take a coral that seems to be resistant to climate change and use that as the seed stock to propagate and put out on a different reef that might be degraded. The cool thing was we didn’t see any differences in their bleaching response after this transplant.

 

What was novel is that we had this highly replicated experiment, and we saw no change in the coral’s bleaching response.

Transplanted Bleaching-Resistant Coral Retain Their Resistance To Heat
Marine biologist looks at coral growing on mats underwater. (Image: S. Matsuda)

However, even though the corals thrived, they weren’t entirely unaffected. The location did appear to impact the corals’ reproduction rates. A coral’s native site conditions affected its future reproductive fitness.

Barott said:

The corals from the ‘happy’ site – the outer lagoon that had higher growth rates before the bleaching event – generally seemed a little happier, and their fitness was higher. That tells us that if you’re going to have a coral nursery, you should pick a site with good conditions because there seems to be some carryover benefit of spending time at a nicer site even after the corals are out-planted to a less ‘happy’ site.

 

The “happy” site, the lagoon farther from shore, had higher flow rates than the other reef, which is closer to shore, less salty, and more stagnant. Higher flow rates are significant for helping corals get rid of waste and get food.

While the study is promising as a seeding strategy for vulnerable coral reefs, it should be seen as a temporary solution to the threat of global warming.

Barott said:

I think techniques like this can buy us a little bit of time, but there isn’t a substitute for capping carbon emissions. We need global action on climate change because even bleaching-resistant corals aren’t going to survive forever if ocean warming keeps increasing as fast as it is today.

Barott is continuing to pursue research on coral resiliency, including an investigation of how heat stress and bleaching affect reproductive success and the function of coral sperm.

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