KAILUA-KONA — Somewhere between 38 and 92 percent of West Hawaii’s reefs will be declared bleached and dead, once scientists are comfortable enough with their figures to release final results this summer.
KAILUA-KONA — Somewhere between 38 and 92 percent of West Hawaii’s reefs will be declared bleached and dead, once scientists are comfortable enough with their figures to release final results this summer.
Those numbers are based on 200 dives at 40 reef sites ranging from Kawaihae to Keauhou, conducted late last year by The Nature Conservancy during the height of bleaching because of El Nino.
Scientists have not yet pegged a firm mortality figure, but even that will be a moving target, with reefs standing to get worse before they get better.
Hawaii’s building blocks of nearshore marine biodiversity have already seen two years of unprecedented die-off, and scientists with the National Oceanic and Atmospheric Administration say a third year of bleaching is likely to last until the end of 2016, with warmer waters taking a toll that is both ongoing and as yet not completely quantified.
The ocean is transitioning from El Nino to La Nina, a period of cooler water temperatures. But those cooling effects will take some time to get established here.
It’s time for soul-searching, scientists say.
That means thinking about bleaching and warmer water due to climate change as if they’re here to stay rather than just visiting, said Eric Conklin, director of marine science for The Nature Conservancy of Hawaii.
“It’s a wakeup call,” Conklin said. “We need to be thinking really hard and carefully about the steps we want to take as a community.”
Coral reefs support the most species of any marine environment, hosting countless kinds of fish, invertebrates and even mammals, where they breed and eat. It’s die-off could lead to a collapse of the marine ecosystem.
TNC is trying to understand which coral species can survive the best when challenged with such events as the record influx of warm water that brought temperatures as high as 86 degrees to the nearshore waters during last year’s peak in the El Nino cycle. Conservancy scientists and others are trying to get a handle on what policy changes will help stem the changing tide.
Coral’s ability to survive warm water and quickly colonize available surfaces are keys to resilience on the reef. But humans can do their part by reducing overfishing of the species that help coral by eating algae off the reefs, and by reducing polluted runoff into nearshore waters, Conklin said.
Scientists are pooling their information to try to determine what makes a reef bounce back, and the stressors that might be inhibiting recovery.
Convention holds that coral in deep water will fare better than its shallower neighbors. But surprisingly, that has not been the case in studies out to 45 feet of depth on Hawaii Island, Conklin said. The waters off South Kohala saw the worst bleaching in relation to areas farther south, according to TNC, with cauliflower coral faring most poorly among the species. Lobe coral, which is abundant and creates a lot of reef structure, fared much better, and finger coral ran about in the middle of the pack, Conklin said.
Faced with reef death on a scale they’ve never witnessed before, scientists are even farming resilient coral species to foster strains that can face a warmer future.
Chad Wiggins, Hawaii Island’s marine director for TNC, said reef managers have to make hard choices about where to invest limited resources.
“We need to understand which reefs have the best chance of surviving into the future,” he said. “This means understanding which reefs are healthiest, as well as which are doing poorly and why.”