HONOLULU – Warm ocean temperatures have caused large expanses of coral to bleach in the pristine reefs northwest of Hawaii’s main islands, scientists said Tuesday.
Mass bleaching has occurred at Lisianski atoll, about 1,000 miles northwest of Honolulu, said Courtney Couch, a researcher at the Hawaii Institute of Marine Biology. Coral also bleached at Midway, and at Pearl and Hermes atolls, but not as severely.
Couch called the situation “dire,” particularly for Lisianski. In one shallow part of the reef, 90 percent of the coral was bleached, she said. An average of 35 percent of the coral sites observed at the atoll had bleached, she said.
“It’s a pretty big deal. Especially after looking at the forecasts for thermal stress over the next month. It’s pretty much predicted to stay at this point for the next month and then peter off at the end of October,” Couch told reporters after returning from two research trips this summer.
Mass bleaching generally occurs when corals are stressed by warmer-than-normal temperatures. The warm water prompts algae inside the coral to leave, which starves coral and turns it white.
Algae may return to coral, and the coral may recover, depending on how long the bleaching lasts.
Coral start to die after about eight weeks of high temperature-induced stress, Couch said. This year, Lisianski has had 10 weeks. Midway, Pearl and Hermes atolls have had seven.
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