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Professor says state’s reefs have chance to bounce back from bleaching

Updated: 
April 21, 2017 - 12:05am

HONAUNAU — A rather obsolete mindset concerning Hawaii’s strained reef systems re-emerged among attendees after listening to a presentation on coral bleaching Wednesday evening — optimism.

Hawaii couldn’t escape the worst global bleaching event in history in 2015, which bleached nearly 90 percent of corals that year and killed almost half of the coral off the coast of West Hawaii.

At her forum covering the devastating environmental development Wednesday night at Puuhonua O Honaunau National Historical Park, Katryn Wiese — professor of Geology and Oceanography at City College of San Francisco — said there are indications the state’s reefs are poised to rebound better than most affected coral across the globe.

“It looks like Hawaii is not going to be subjected to another coral bleaching event this year, although we have to keep track and look at it pretty regularly to see,” Wiese said. “If it doesn’t, then the corals will have a chance to regrow.”

The two primary threats to coral are rising ocean temperatures facilitated by global warming and pollution, such as sewage runoff, which is prevalent in Hawaii.

While Wiese explained ocean temperatures will continue to rise no matter what, natural weather patterns may spare Hawaiian waters just enough to create conditions that might allow coral to bounce back. Those chances are tied specifically to El Nino, a naturally occurring, reversing climate pattern that can change water temperatures by between 1-3 degrees Celsius.

El Nino impacts Hawaiian reef systems by raising water temperatures and exacerbating the effects of global warming.

Coral bleaching is actually a regular occurrence in the Pacific Ocean historically, Wiese said, and bleached corals don’t necessarily equate to dead corals. Depending on the species of coral, they may survive anywhere from 2-5 years in a bleached condition. Thus, the problem isn’t that corals are exposed to increased heat, it’s that they’re exposed to that heat for too long to sustain themselves.

Wiese said experts predict a 60 percent probability that bleaching caused by thermal stress will occur between April and July at several sites worldwide, in part because of a persistent El Nino. However, it appears Hawaii may be spared that extra stress, creating room for optimism regarding the outlook on the state’s coral reef systems.

“We have been in an El Nino for the last two years, and at least for some of the most taxed reefs in the world including the entire Western Equatorial Pacific, they’re expecting another El Nino yet again. It looks like they’re going to end up with three years of coral bleaching events,” Wiese said. “Hawaii is fortunately, at least at the moment, out of that. So Hawaii has a chance to potentially regrow some of its coral before it’s subjected to another one of these events.”

Paul Suppo, an avid diver and snorkeler on the Big Island, said he was unaware previously of the capacity of coral to rebound after bleaching events as well as the impact natural weather patterns like El Nino had on the process.

Coral Mack, a former teacher and current resident of Hawaii Island, left the meeting with a more positive outlook on coral bleaching than she’s held in a long while.

“I’m more optimistic about what’s happening in Hawaii given what (Wiese) was saying,” Mack said. “We don’t have all the stress I thought we had.”

Still, Wiese said even a spot of luck in 2017 won’t reverse the long-term trend of increased thermal stress on Hawaiian coral — a stress that could permanently alter the underwater landscape throughout the tropics and beyond.

Rising ocean temperatures rendering waters off Hawaii less able to sustain coral will also heat up areas further north and south of the equator that were previously too cold to support reef systems. Coral can clone itself and migrate, creating new systems elsewhere.

Thus, coral reefs aren’t necessarily going to disappear completely due to global warming, but instead relocate. Migrating coral reefs would alter fish populations, damaging the fishing industry and creating other negative economic consequences for the places they vacate — such as a decrease in tourism.

The National Oceanic and Atmospheric Administration (NOAA) has estimated coral reefs may contribute a value upward of $375 billion annually in goods and services they provide worldwide, including jobs their existence creates.

Environmentally, reefs also aid in the prevention of erosion, property damage and human casualties from storms. NOAA also cites the protection coral reefs provide the wetlands, ports and harbors they border.

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