Record coral kill off on Great Barrier Reef
By Martin Parry, AFP
December 1, 2016, 12:02 am TWN
SYDNEY--A mass bleaching event on the Great Barrier Reef this year killed more coral than ever before, scientists said Tuesday, sounding the alarm over the delicate ecosystem.
The 2,300-kilometer (1,400-mile) long reef — the world's biggest — suffered its most severe bleaching in recorded history, due to warming sea temperatures during March and April, with the northern third bearing the brunt.
Follow-up underwater surveys, backing earlier aerial studies, have revealed a 700-kilometer stretch of reefs in the less-accessible north lost two-thirds of shallow-water corals in the past eight to nine months.
"Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef," said Terry Hughes, head of the Centre of Excellence for Coral Reef Studies at James Cook University.
"This region escaped with minor damage in two earlier bleaching events in 1998 and 2002, but this time around it has been badly affected."
Further south over the vast central and southern regions, including major tourist areas around Cairns and the Whitsunday Islands, there was a much lower toll.
Bleaching occurs when abnormal environmental conditions, such as warmer sea temperatures, cause corals to expel tiny photosynthetic algae, draining them of their color.
Algae are vital to the coral, which uses the organic products of photosynthesis to help it grow.
The loss of algae makes the host vulnerable to disease and means it will eventually die. However, coral can recover if the water temperature drops and the algae are able to recolonize them.