1 of 6
Hawaii Department of Land & Natural Resources, Dan Dennison, Associated Press
This Jan. 20, 2015 photo released by Hawaii Department of Land & Natural Resources shows a researcher swimming above coral being studied for bleaching, which is a stress response that causes corals to lose algae and color from their tissue, in Kaneohe Bay near Kaneohe, Hawaii. Warm ocean temperatures last summer stressed many of Hawaii’s coral reefs so severely that they expelled the algae they rely on for survival. The resulting mass “bleaching” of Hawaii’s corals is a blow to the state’s fragile reefs which are already under pressure from runoff from development on land and overfishing. It’s also a concerning indicator of a warming globe, with some activists calling coral bleaching the most visible sign of climate change.

HONOLULU — Hawaii's corals are recovering after being stressed by warmer-than-normal ocean temperatures last year.

But scientists warn the strain of being in warmer water weakened them. This makes the coral more susceptible to disease. The coral are also now more likely to die the next time the waters around them heat up.

The state Department of Land and Natural Resources said Thursday the coral bleaching that occurred during the warming event was the worst on record for Hawaii.

The phenomenon is called bleaching because warm water prompts coral to expel their algae and lose their color.

Mark Eakin coordinates the Coral Reef Watch program at the National Oceanic and Atmospheric Administration. He says the bleaching demonstrates climate change isn't in the distant future but is happening now.