Rising coral stress
Greg Asner, the director of Arizona State University's Center for Global Discovery and Conservation Science, reviews ocean temperature data at his lab on the west coast of the Big Island near Captain Cook, Hawaii. 
"You have things like two giant volcanoes on the Big Island blocking the predominant trade winds," making the island's west coast, where Papa Bay sits, one of the hottest parts of the state, Gove said. He said he expects "severe" coral bleaching in those places.
"This is widespread, 100% bleaching of most corals," Gove said. And many of those corals are still recovering from the 2015 bleaching event, meaning they are more susceptible to thermal stress.
According to NOAA, the heat wave's causes include a persistent low-pressure weather pattern between Hawaii and Alaska that has weakened winds that otherwise might mix and cool surface waters across much of the North Pacific. What's causing that is unclear: It might reflect the atmosphere's usual chaotic motion, or it could be related to the warming of the oceans and other effects of human-made climate change.
Beyond this event, oceanic temperatures will continue to rise in the coming years, Gove said. "There's no question that global climate change is contributing to what we're experiencing," he said.
For coral, hot water means stress, and prolonged stress kills these creatures and can leave reefs in shambles.
