The distinctive geographic footprints of recurrent bleaching on the Great Barrier Reef in 1998, 2002 and 2016 were determined by the spatial pattern of sea temperatures in each year. In a statement last week, the Marine Park Authority’s Director of Reef Recovery said the first aerial survey of the Reef this year showed “severe bleaching” in offshore reefs.
Coral surveyor Margaux Hein swims over a field of recently dead branching corals, northern Great BarrierReef, October 2016. In 2016 that figure shot up to a devastating 50 percent. That was the third and worst sever bleaching.
Coral bleaching takes place when corals that live in tropical waters start releasing colorful algae from their tissues, exposing their white, calcium carbonate-made skeletons.
On the cover this week: Reefs under threat. “How this event unfolds will depend very much on local weather conditions over the next few weeks”. “Once global temperatures stabilise, then reefs will have time to adapt and catchup”.
Professor Pandolfi is one of 46 researchers who contributed to the Nature report. “A fourth event after only one year is a major blow to the Reef”. “We’re seeing these happening more frequently, they’re longer lasting and the geographic distribution is spreading”.
The culprit is global warming, say the authors, with damaged reef areas corresponding directly with ocean temperature, which the National Ocean and Atmospheric Administration (NOAA) said set records in 2015 and 2016.
“It broke my heart to see so many corals dying on northern reefs on the Great Barrier Reef in 2016”, said Hughes.
It was previously suggested that while climate change did pose a major threat to the reef, this could be mitigated by cleaning up the water and preventing overfishing. Prof. Morgan Pratchett, also from James Cook University, told the BBC that the “window of opportunity” to stop the impact of emissions was closing.
In 2016, the coral reef, which constitutes the world’s largest living organism, suffered the worst bleaching event in its 20 million year history.
The researchers found bleaching occurred regardless of how protected the reef was from run-off and over-fishing. A new bleaching event is under way now.
Sadly, however, corals are also highly sensitive to temperature changes. “We can ask questions like, are they more likely to bleach this year, for a given level of heat exposure, because they’re still physiologically damaged from last year?”
It’s massive ecosystem of coral and fish enters into a food chain that helps feed neighbouring countries, finance Australian economic growth and, as the basis for countless documentaries, inspire generation after generation of scientists.
“Things are changing even faster than many of us feared”, Connolly said.