Scientists have discovered that most of the coral is dead – in what had been one of the world’s most isolated tropical marine reserves.

Researchers  on an emergency undersea expedition have described what they called “a graveyard of coral”  around Jarvis Island in the Pacific Remote Island Marine National Monument.

Back in November much of the coral had bleached white – but was alive.

Scientists now say the coral is 95 per cent dead.

National Oceanic and Atmospheric Administration’s Mark Eakin says the culprit is El Nino – the natural warming of parts of the Pacific – which changes weather around the world – assisted by man-made warming.

Normally, a unique ocean current brings cold water up from the deep water – to make that underwater region vibrant with coral, plankton, fish and sharks.