This photo taken on November 20, 2014 shows an
aerial view of the Great Barrier Reef off the coast of the Whitsunday
Islands, along the central coast of Queensland.
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SYDNEY
- More corals are dying and others are succumbing to disease and
predators after the worst-ever bleaching on Australia's iconic Great
Barrier Reef, scientists said Wednesday.
A swathe of corals bleached in the northern third
of the 2,300-kilometre (1,429-mile) 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".
"In March, we measured a lot of heavily bleached branching corals
that were still alive, but we didn't see many survivors this week,"
Andrew Hoey of the Australian Research Council Centre of Excellence for
Coral Reef Studies at James Cook University said in a statement.
"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."
Researcher Greg Torda said of the reefs surveyed near Lizard Island
off Cairns -- a gateway to the giant ecosystem -- the amount of live
coral covering them fell from about 40 percent in March to under five
percent.
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 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 percent 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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Course: The Nation (26-10)
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