Oceans worldwide are undergoing the third global coral bleaching event which could impact 38 per cent of the planet's coral reefs by the end of this year and kill over 12,000 square kilometres of reefs, according to a new report.
As record ocean temperatures cause widespread coral bleaching across Hawaii, scientists confirm the same stressful conditions are expanding to the Caribbean and may last into the new year, prompting the declaration of the third global coral bleaching event ever on record.
"The coral bleaching and disease, brought on by climate change and coupled with events like the current El Nino, are the largest and most pervasive threats to coral reefs around the world," said Mark Eakin, Coral Reef Watch coordinator at the US National Oceanic and Atmospheric Administration (NOAA).
"What really has us concerned is this event has been going on for more than a year and our preliminary model projections indicate it's likely to last well into 2016," said Eakin.
The event is expected to impact approximately 38 per cent of the world's coral reefs by the end of this year and kill over 12,000 square kilometres of reefs, according to globalcoralbleaching.Org.
While corals can recover from mild bleaching, severe or long-term bleaching is often lethal.
After corals die, reefs quickly degrade and the structures corals build erode. This provides less shoreline protection from storms and fewer habitats for fish and other marine life, including ecologically and economically important species.
Although reefs represent less than 0.1 per cent of the world's ocean floor, they help support approximately 25 per cent of all marine species.
As a result, the livelihoods of 500 million people and income worth over USD 30 billion are at stake, researchers said.
Coral bleaching occurs when corals are exposed to stressful environmental conditions such as high temperature. Corals expel the symbiotic algae living in their tissues, causing corals to turn white or pale.
Without the algae, the coral loses its major source of food and is more susceptible to disease.
The first global bleaching event was in 1998, which killed 16 per cent of the coral reefs around the world during a strong El Nino that was followed by an equally very strong La Nina. A second one occurred in 2010.
NOAA estimates that by the end of 2015, almost 95 per cent of US coral reefs will have been exposed to ocean conditions that can cause corals to bleach.
The biggest risk right now is to the Hawaiian Islands, where bleaching is intensifying and is expected to continue for at least another month, researchers said.
The next concern is the further impact of the strong El Nino, which climate models indicates will cause bleaching in the Indian and southeastern Pacific Oceans after the new year. This may cause bleaching to spread globally again in 2016.
