Scientists say warm ocean temperatures are causing large expanses of coral to bleach in the pristine reefs northwest of Hawaii’s main islands.
Courtney Couch, a researcher at the Hawaii Institute of Marine Biology, said she observed mass bleaching at Lisianski atoll, about 1,000 miles northwest of Honolulu.
Coral also bleached at Midway, and at Pearl and Hermes atolls, but not as severely, the scientists found.
Mass bleaching occurs when corals are stressed by warmer-than-normal temperatures.
The warm water prompts algae inside the coral to leave. This starves coral and turns it white.
Coral starts to die after about eight weeks of high temperature-induced stress. This year, Lisianski has had 10 weeks. Midway and Pearl and Hermes atolls have had seven.
The Northwestern Hawaiian Islands last had a mass bleaching event in 2004.