Environment

Aerial survey reveals extent of coral bleaching on Great Barrier Reef

Aerial survey reveals extent o...
A recently completed aerial survey of the Great Barrier Reef has confirmed that a coral bleaching event is taking place for the second consecutive year
A recently completed aerial survey of the Great Barrier Reef has confirmed that a coral bleaching event is taking place for the second consecutive year
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Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
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Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
A recently completed aerial survey of the Great Barrier Reef has confirmed that a coral bleaching event is taking place for the second consecutive year
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A recently completed aerial survey of the Great Barrier Reef has confirmed that a coral bleaching event is taking place for the second consecutive year
Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
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Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
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Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
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Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
Indication of the bleaching taken at Mission Beach
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Indication of the bleaching taken at Mission Beach
Indication of the bleaching taken at Mission Beach
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Indication of the bleaching taken at Mission Beach
Indication of the bleaching taken at Mission Beach
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Indication of the bleaching taken at Mission Beach
Indication of the bleaching taken at Mission Beach
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Indication of the bleaching taken at Mission Beach
Bleached coral at Beaver Reef
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Bleached coral at Beaver Reef
Orpheus Island
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Orpheus Island
This illustration highlights the southward creep of the bleaching from last year to current
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This illustration highlights the southward creep of the bleaching from last year to current

After a study last month revealed that the Great Barrier Reef was suffering a coral bleaching event for the second consecutive year, scientists have completed an aerial survey of the reef offering more evidence of the environmental catastrophe that is currently taking place.

Before this year there had been three major bleaching events identified in the modern history of the reef - 1998, 2002 and 2016. Researchers last month identified the signs of another bleaching event taking place this year, but it wasn't until the visual surveys were completed that the situation could be definitively confirmed.

The same scientists who undertook observations in 2016 recently completed an aerial survey of the reef covering more than 8,000 km (5,000 mi), examining 800 individual coral reefs. The survey identified new patches of bleaching across the middle third of the reef, an area previously undamaged in the 2016 event.

This illustration highlights the southward creep of the bleaching from last year to current
This illustration highlights the southward creep of the bleaching from last year to current

The back-to-back bleaching events, and the increased spread south of the damage now leaves only the southern third of the reef untouched, and while bleached coral doesn't necessarily mean the coral is dead, the dual impact of these losses decreases the reef's natural ability to repair itself.

"It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016," explained Dr James Kerry, who was part of the recent aerial surveys.

In tandem with this new bleaching event, a 100-km (62-mi) corridor of the reef was recently damaged by Tropical Cyclone Debbie in late March. Despite the cyclone potentially offering a cooling effect that could have mitigated the ongoing bleaching, the researchers noted that the damage caused by the violent weather pattern rendered any positive effects negligible.

Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns
Photographs of the Great Barrier Reef coral bleaching stretching from Townsville to Cairns

"Clearly the reef is struggling with multiple impacts," explains Professor Terry Hughes, who undertook the recent surveys with Dr James Kerry. "Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events: 1° C (1.8° F) of warming so far has already caused four events in the past 19 years."

The scientists noted that this year's mass bleaching seems to be occurring without the assistance of El Nino weather patterns, which highlights the impact of global warming and general sea temperature rises as the primary culprit.

Source: ARC Centre of Excellence for Coral Reef Studies

11 comments
ripshin
The bleaching event appears to be caused, primarily, by sea levels falling. This, by the way, is consistent with the el Nino just experienced, as the massive pool of warm water that collected in the west flows east. No need to cite climate change as this is part of the natural cycle. Furthermore, bleaching of the exposed coral, left out to dry by receding sea levels doesn't really offer any indication of the overall reef health. Unexposed coral is likely fine. But this should be checked. Can't do it from the air, though. They'll have to get down there and start investigating personally. Finally, citing climate change as some type of culprit for the warming of the shallow reef water is really tiresome. The specific heat capacities of water and air basically ensure that there's no physical mechanism by which the air can heat the water (this is not a static system the can eventually reach equilibrium). The upper xx meters of the ocean is heated by direct sunlight not by conductive heat transfer from air to water. Nor is it heated by the long wave infrared back radiation postulated from CO2. Infrared radiation will heat the top few millimeters of the ocean at best (probably more like the top few microns) which will quickly evaporate. It's actually quite a complex interchange, which is poorly understood and not even a part of the GCMs (AFAIK). So, again, per a recent comment I made, this is all pretty easy stuff that doesn't require a genius level intellect to think through. The more I read about this stuff, the more I question the whole climate change narrative. When something is blamed for everything, it sounds more like a political tool than actual science. rip
KeithLehman
Ripshin has posted a sensible reasoning for this phenomenon. While scientists remain focused upon CO2 issue, they are ignoring another aspect of climate change and weather anomalies - solar activity. Ripshin is correct that the climate change argument with junk scientists is based on politics, not real science. For scientists it is an extension or addition of funding. For politicians it is the fear tool using doomsday climate scenarios as a means for getting votes, election funding, excuse for more or increased taxation, and control. Drop in water depth as ripshin mentions is one factor "scientists" are ignoring, which also disproves the theory that the ice at the poles is melting more than usual and causing sea levels to rise. It is naive for people to believe the politicians and junk scientists into thinking that funding them and legislation is going to control a natural climate and weather anomaly.
Bruce Warren
Why is it an 'environmental catastrophe' when coral dies? Why it is called 'bleaching'? There is no Chlorox involved. Every living creature dies at some time. And it seems to me that the result of dead polyps is a static reef, like so many around the world. The 'environment' is not harmed by reefs not growing. The reef remains, other creatures still live and breed there. This is totally another eco-freak attempt to invent more problems that need 'government solutions' that restrict what us humans can do. The eco-system has a few billion more years of experience than us humans and knows how to adapt and thrive no matter what humans beings do.
ljaques
The perfect solution for this is to melt more glaciers into the ocean to cool the water and make it deeper, preventing all bleaching of the coral. In order to achieve this, we will have to switch 100% of electrical production to coal, adding heat to the upper atmosphere in order to melt the glaciers. Sound like a plan, guys and girls? Good. Let's begin. <vbg>
Fretting Freddy the Ferret pressing the Fret
Surely, ocean acidification should be another big player on adversely impacting the Great Barrier Reef. That's also because, you guessed it, caused by CO2 emitted from human activity.
MartinVoelker
The connection between Global Warming and coral bleaching is well studied and understood. Coral reefs operate near to their upper limit of heat tolerance, and will start 'bleaching' if that threshold is breached even for a week, which is why El-Nino events have such a big impact. But with the current speed of ocean warming as a function of climate change corals cannot evolve fast enough.
chase
@ Bruce Warren - It's called "bleaching" because the corals turn white, a similar effect of putting bleach on clothes. Once a reef dies... the fish move on. See Jacque Cousteau's film in which he revisits reefs that once flourished and were dead upon his return. Yes there are a few fish that hang around but overall it's like a lush forest turned desert. Corals are fickle... they are barometer's in the same manor amphibians are to changes, problems, pollution, be them man made or natural. In short, of the reefs die, it makes a huge impact on the food chain in the ocean. Combine that with natural and a high human consumption rates... well... to add up where this is going, it's kindergarten math.
highlandboy
A few items that may be helpful in this discussion: As any diver knows the more varied coloured corals occur in the first 10m (even dive lights do not reveal much colour variation below 15m). So loss of colour is easily seen from aerial surveys. Reduction in depth or more varied tides across the barrier reef are not being seen as proposed by #ripshin. Gravity ensures water levels remain constant (within the tidal effects) unless there is a volume change. There is no loss of water level across the reef. The loss of colour is a result of the coral polyps expelling their algae symbiotes (algae are embedded in the polyps flesh. The polyps provide a secure environment and pass nutrients to the algae. The algae use photosynthesis and expel sugars for the polyps). The loss of the polyps cause loss of colour. They expel the polyps for a variety of reasons. These include: toxins, increased levels of water borne nutrients, increased levels of UV light and of course the oft quoted increase of temperature. The algae are reabsorbed if these levels are restored for adequate time. Long term expulsion due to any of the above causes a loss of colour (polyps are clear and the calcium carbonate support is white) is referred to as coral bleaching and has nothing to do with bleaches (chlorine or otherwise) but with the loss of colour. Reefs which lose their coral quickly become covered with algae, and rapidly lose their biodiversity. Once habitat is lost it is not readily reestablished. If we lost all coral reefs it would be similar to losing all rain forests. The coral bleaching is not a single factor problem. While it occurs mainly in the north, earlier bleaching events have been in areas closer to the agriculturally developed areas of land.
Anne Ominous
It is also apparent from the aerial photos themselves that it is precisely where the water has become very shallow, or indeed the reef is dry part of the day, that the reefs becomes bleached. There have been recent studies which confirm this. So while bleaching is often blamed on CO2, greenhouse warming, and "acidification", there are other less esoteric causes which are right in front of us which have largely been ignored, especially in the press.
Anne Ominous
@ highlandboy In fact, shallower seas are indeed being found along most of the GBR, and the sea level has become lowest precisely in those areas where the bleaching is strongest. https://wattsupwiththat.com/2017/04/05/falling-sea-level-the-critical-factor-in-2016-great-barrier-reef-bleaching/ The data clearly support this.