Coral in equatorial Pacific, north Pacific and western Atlantic oceans are facing threats from warm ocean temperatures, said National Oceanic and Atmospheric Administration on Monday. Changes in coral environment causes coral bleaching, which in turn releases algae residing in its tissue.

Color of the coral turns pale or white and they become vulnerable to diseases. They succumb to diseases in extreme cases and pose the risk of irreversible damage to the habitat for fish and shellfish.

“The bleaching that started in June 2014 has been really bad for corals in the western Pacific. We are worried that bleaching will spread to the western Atlantic and again into Hawaii”, said Mark Eakin, NOAA’s Coral Reef Watch coordinator, in a news release on Monday.

Overall climate change and El Nino weather patterns have increased the temperature of oceans. However, Eakin said the overall warming is a bigger concern than individual weather patterns, as suggested by the frequency of these events.

Global warming is having an intense effect on oceans, making the corals more susceptible, he said. Bleaching risk is greatly posed by ocean temperatures, light and nutrient levels. However, NOAA says the widespread bleaching could be the result of warm temperatures alone, something that scientists have largely witnessed since last year.

Widespread bleaching took place in Hawaii for the first time in 2014 in nearly two decades. Its emergence again, if happens, this year would mean consecutive years of bleaching for the first time in history of the Hawaiian Islands.