Great Barrier Reef faces serious coral bleaching risk
The next few weeks are critical for the Great Barrier Reef as they face the impacts of what authorities have called the longest-ever global coral bleaching event on record.
On Tuesday, the Great Barrier Reef Marine Park Authority announced that low level bleaching had been recorded on the reef, particularly in shallow areas that are more exposed to the sun.
"At this stage, there appears to be low rates of coral mortality restricted to a small number of reefs," GBRMA chairman, Russell Reichelt, said in a statement. "Fortunately, what we're seeing right now on the Great Barrier Reef is much less severe than what’s happened across the Pacific during the current global bleaching event."
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Neal Cantin, who leads the Australian Institute of Marine Science's efforts to document coral bleaching, told Mashable Australia his team has started to see the early signs. "There are reports of bleaching in the north [of the reef] at Lizard Island, in the central sector near Townsville, as well as the southern areas near Mackay," he said.
When faced with stresses such as rising water temperatures, coral can expel the algae that lives in its tissue, and that gives it colour and energy. Known as coral bleaching, this causes the coral to expose its skeleton, leaving it more vulnerable to disease, pollution and other risks.
In late 2015, the U.S. National Oceanic and Atmospheric Administration announced this bleaching event, which is the third such global occurrence ever documented, was underway. Thanks to a strong El Niño climate event and human-made global warming, the coral die-off around the world could continue into 2017, making it the longest such event on record, NOAA said in an emailed statement on Feb. 23.
Around 500 million people around the world depend on reefs for food and the protection they offer the coastline from storms, according to NOAA, and it has been estimated the Great Barrier Reef is worth approximately A$5.7 billion (US$4.1 billion) each year to the Australian economy from tourism and other industries.
In the last two weeks, the Great Barrier Reef region has experienced prolonged warming above normal summer temperatures, Cantin said. "We haven't had very much rain in the last month and a half in Queensland, which leads to clear conditions and the sun heating the ocean more than it typically would."
What happens to the coral could all depend on the weather over the next few weeks. "We're hoping the wind that picked up this week will help cool things off," he said.
Reichelt said authorities are also hoping for grey days. "If we're fortunate enough to receive plenty of cloud cover, which will effectively provide shade, it will go a long way to reducing heat absorption by the ocean and alleviating thermal stress on corals," he added.
The Great Barrier Reef, while it is the most well known, is not the only reef at risk in Australia. The west coast's large reef system is also facing a severe impact. "The model projects probably more warming happening on the west coast at this point," Cantin said. "The risk for bleaching on the west coast is equal to the Great Barrier Reef, if not higher."
Along with the El Niño, global bleaching events are driven by global warming, Cantin warned, and they're occurring more and more frequently. "We've had two major bleaching events [in the Great Barrier Reef] in 1998 and 2002, and we're potentially facing another mass bleaching event this year," he said. "That's three big events in the last 15 years."
The reef suffered significant and ongoing damage after each occurrence, Cantin said. "During those events, 40-50% of the entire [Great Barrier Reef] system suffered bleaching," he explained. The time a reef takes to recover from such an event depends on its severity, he continued, but it typically takes 5-15 years to return to pre-disturbance levels. Recovery can also be stymied by repeated bleaching events.
According to Cantin, the Great Barrier Reef is potentially slightly less vulnerable to bleaching than reefs in other regions. "The Great Barrier Reef is a diverse system. It's made up of more than 300 individual species, and that diversity helps reduce the risk," he explained, comparing it to reefs in the Caribbean that he said contain only around 30 species.
"The diversity [in the Great Barrier Reef] basically gives you a spectrum of tolerance and sensitivity," he said. "You've got individual species that are more sensitive than others, and you've got community species that are tolerant and may be able to survive these events better."
Still, Australian scientists will be hoping for rain and cloudy days in the month to come.
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Ariel Bogle was an associate editor with Mashable in Australia covering technology. Previously, Ariel was associate editor at Future Tense in Washington DC, an editorial initiative between Slate and New America.
