Rising sea temperatures killed 34% of Guam's coral reefs between 2013 and 2017, University of Guam researchers said Monday.

About 60% of the reefs along Guam's eastern coast are gone.

"Never in our history of looking at reefs, have we seen something this severe," said Laurie Raymundo, UOG marine lab director and marine biology professor.

"The highest temperatures we've ever recorded in Guam happened in 2017," Raymundo said. "Right now, the best way to stop bleaching is to lower our carbon footprint."

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Corals are vital to fish habitats, provide coastal protection and contribute to the island's tourism industry, so the problem is too urgent to ignore, Raymundo said.

Reducing local stressors can also help, such as addressing the island's pollution, sewage system, plastic-waste and human impacts, Raymundo said. However, the problem lies in the elevated global carbon dioxide output, beyond just Guam.

"It's what we're pumping into the atmosphere that is creating warmer temperatures," she said. "There's enormous countries, with enormous populations, and we know which ones they are, that are responsible for the vast majority of carbon going into the environment. And it's not small islands like Guam, nonetheless, we are affected by it."

Chance of mass coral bleaching

Raymundo, David Burdick, a research associate with the UOG Marine Lab, and Whitney Hoot, coral reef resilience coordinator with the Guam Bureau of Statistics and Plans, co-authored a new study on the region's reefs published in the journal, "Coral Reefs."

The problem is ongoing, too, researchers said. Guam is currently in a watch status for another mass bleaching event, which is a precedent to mass death of reefs.

The watch is expected to increase to an alert status one within a month, which means there is a chance of mass coral bleaching this year, and may reach alert level two within five to eight weeks, which signals that coral death is likely.

"We have a system in place now to deal with these events," Hoot said. "Once we see temperatures starting to rise, this is when we activate our plan."

The Guam Coral Reef Response team, a multi-agency team, consistently monitors the island's reefs, and revives coral communities in line with a comprehensive coral reef recovery plan established in 2017.

Corals planted in Piti and Asan

Meanwhile, restoration is underway, according to Hoot. The organization planted corals in Piti and Asan in April and May. The corals planted were taken from native populations on Guam that survived the mass bleaching from 2013 to 2017.

"One thing we can assume is that the corals that survived are probably pretty tough, pretty hardy," Hoot said. "So those served as the starter corals for the coral nursery."

There will be another bleaching event, and there may be one this year. The key is to ensure a healthy local environment for the corals to recover and thrive in the meantime, Burdick said.

"Is there clean water? Is there very little algae to compete with the corals?" he said. "Give them a fighting chance."

Protection of coral reefs is a focus for Gov. Lou Leon Guerrero too. The governor signed an executive order in June to implement a new coral reef resiliency strategy on Guam.

"The people at this table do not believe coral reefs are on their way out," Raymundo said. "We do know that some species will be lost."

Residents can report coral bleaching and other reef concerns at http://eormarianas.org/quick-report/.

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