Australia: New photos show worst coral bleaching to date: A third of the Great Barrier Reef is affected

You can of course prove anything with photos. The previous reports from this lot were found to be vastly exaggerated so this report should also be taken with a large grain of salt.  Reading between the lines, I gather that most of the reef has already recovered from the earlier bleaching but the recovery has been uneven so far.

More corals are dying and others are succumbing to disease and predators after the worst-ever bleaching on Australia's iconic Great Barrier Reef.

A swathe of corals bleached in the northern third of the 1,429-mile (2,300-kilometre) long biodiverse site off the Queensland state coast died after an unprecedented bleaching earlier this year as sea temperatures rose.

And researchers who returned to the region to survey the area this month said 'many more have died more slowly'.

On the surface, coral bleaching looks like white, bleached-out coral reefs - quite a departure from the usual colourful structures.

Bleaching occurs when abnormal environmental conditions, such as warmer sea temperatures, cause corals to expel tiny photosynthetic algae, draining them of their colour.

Andrew Hoey, from the Australian Research Council Centre of Excellence for Coral Reef Studies at James Cook University, said: 'In March, we measured a lot of heavily bleached branching corals that were still alive, but we didn't see many survivors this week.

'On top of that, snails that eat live coral are congregating on the survivors, and the weakened corals are more prone to disease. 'A lot of the survivors are in poor shape.'

Greg Torda, whose team recently returned from re-surveying reefs near Lizard Island, said the amount of live coral covering the island fell from about 40 per cent in March to under five per cent.

It is the third time in 18 years that the World Heritage-listed site, which teems with marine life, has experienced mass bleaching after previous events in 1998 and 2002.

The researchers said even though they were still assessing the final death toll from bleaching in the north, 'it is already clear that this event was much more severe than the two previous bleachings'. They expect to complete all their surveys by mid-November.

Bleaching occurs when abnormal environmental conditions, such as warmer sea temperatures, cause corals to expel tiny photosynthetic algae, draining them of their colour

The reef's northern 700-kilometre section bore the brunt of the breaching during March and April, with the southern areas 'only lightly bleached and remain in good condition'

The reef's northern 700-kilometre section bore the brunt of the breaching during March and April, with the southern areas 'only lightly bleached and remain in good condition'

The reef's northern 435-mile (700-kilometre) section bore the brunt of the breaching during March and April, with the southern areas 'only lightly bleached and remain in good condition', the scientists added.

'As we expected from the geographic pattern of bleaching, the reefs further south are in much better shape,' said Andrew Baird, who led the re-surveys of reefs in the central section.

'There is still close to 40 per cent coral cover at most reefs in the central Great Barrier Reef, and the corals that were moderately bleached last summer have nearly all regained their normal colour.'

The reef is already under pressure from farming run-off, development, the coral-eating crown-of-thorns starfish as well as the impacts of climate change, with a government report last week painting a bleak picture of the natural wonder.

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