Most of Hawaii's coral recovers

Honolulu - A spokesperson for the Hawaii department of land and natural resources says most of the bleached corals have recovered.

Earlier reports speculated that the higher-than-average ocean temperatures had killed Hawaii's coral reefs last year - a phenomenon called bleaching because coral lose their colour when their surroundings were under threat.

Scientists said the experience weakened the coral, making them more likely to get sick. It's also going to be harder for them to withstand warmer waters in future. Coral rely on algae for food and their survival.

The incident is a blow to the state's fragile reefs, which are already under pressure from runoff from development, overfishing and recreational use of the ocean.

Coral reefs are a critical part of the ecosystem and their health is vital to the ocean environment. Coral cover just one-tenth of the ocean floor but are home to 25% of known marine species. Some fish eat coral and others hide from predators in them. Some species use coral as nursery grounds and some types of shark will frequent coral reefs.

Kaneohe Bay on Oahu's east side suffered the most serious bleaching in the state, which is home to 15% of all coral under US jurisdiction and 75% of the dominant coral species there lost some colour or turned completely white.