Coral bleaching in Hawaii -- Hopefully, the damage is over

Lower sea temperatures could bring positive conditions for stressed coral
Bret YagerWest Hawaii Today 2 Dec 15;

KAILUA-KONA — Hopefully, the damage is over.

Record warm ocean temperatures around Hawaii and an El Nino that closely rivals with the record 1997-98 event have caused unprecedented bleaching of the state’s reefs. However, sea temperatures appear to be returning to normal, bringing hope to scientists that the worst may be over.

Ruth Gates, a research professor with the Hawaii Institute of Marine Biology, said things are looking better under the water, but scientists will be keeping a close eye on the reefs in the coming months.

“Many of the bleached corals in Kaneohe Bay are now showing signs of recovery — that is, their color is returning to normal darker brown rather than very pale brown or white that was the state of play in the middle of the bleaching event in September,” Gates said. “The immediate threat to corals associated with higher than normal sea water temperatures has receded. The longer term impact of the bleaching event remain to be seen, sometimes bleached corals recover but they fail to reproduce the following year. This is not good.”

Ruth said the HIMB will be monitoring bleached corals for at least the next year.

A massive stretch of warm water off the leeward coast drove temperatures to a high of 87 degrees off of Kawaihae in mid-September, and jacked sea temperatures about 5 degrees above normal in peak August and September, according to the National Weather Service. That helped to spread coral bleaching across an estimated 50 percent of our reefs. The water off Kawaihae has since cooled to 82 degrees.

While things may be cooling down, the body of warm water off West Hawaii is still 2 to 3 degrees above normal, said Kevin Kodama, a hydrologist with the National Weather Service in Honolulu. El Nino could keep the ocean’s heat content slightly above normal through the winter, Kodama said.

Beyond the island shores, the sea temperatures associated with El Nino are now very close to the 1997-98 event in the Central Pacific, and exceeds that event west of here, said Axel Timmermann, an oceanographer with the International Pacific Research Center.

“The current event is shifted more to the west compared to the 1997 event, so it is a little bit complicated,” Timmermann said. “What matters for the large-scale global impacts are the temperatures in the Central Pacific, and there we are currently really very close to the recorded October values in the 1997 event.”

On land, El Nino is expected to dry out the Big Island and even cause drought, especially in leeward areas where the winter tends to be the dry season anyway. Fire personnel also expect the dry weather ahead to raise fire danger because of a massive fuel load created when vegetation flourished during heavy rainfall this summer.