Fading to a ghost: coral bleaching

Another irreplaceable loss of global dimensions:

Coral reef monitoring teams have reported mass bleaching of coral reefs off the coast of Thailand, Malaysia, Vietnam, Cambodia and Indonesia while the Maldives, Sri Lanka and reefs off the coast of east Africa have also been hit.

With ocean temperatures reaching record levels and combined with the end of an El Nino episode, scientists fear there could be even more damage to corals as the year continues.

Scientists in Thailand have reported reefs suffering 90% of their corals being bleached and up to 20% of the corals dead.

Olivia Durkin, who is leading the bleaching monitoring at the Centre for Biodiversity in Peninsular Thailand, said: “This year’s severe coral bleaching has the potential to be the worst on record.

“Extensive bleaching, death and disease are reported not only in corals, but giant clams, sea anemones and soft corals are also losing their symbiotic algae.”

Corals are a delicate combination of animal, algae and rock that form intricate undersea structures, providing shelter for thousands of brightly coloured fish and also acting as nurseries for the young of many larger open sea fish.

Coral colonies are made up of polyps, which secrete a stony skeleton that forms the intricate and delicate looking structures. A microscopic algae known as zooxanthellae live within the coral where they convert energy from the sun into food for the coral animals.

Bleaching usually occurs when ocean temperatures exceed a threshold that is around one degree higher than the average seen during the warmest summer months.

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