Can we save the coral reefs?

What’s the worst that could happen to the corals in the near future?

This is a prediction from Unesco: “...all 29 coral-containing World Heritage sites would cease to exist as functioning coral reef ecosystems by the end of this century under a business-as-usual emissions scenario.”

According to Science, the latest global coral bleaching from 2015-2017 is finally over. However, Unesco says 21 of 29 World Heritage reefs have been damaged through heat stress and bleaching. Bleaching occurs when corals expel algae, which provide sustenance through photosynthesis; the corals then turn white and die if the water temperature remains high. Following the latest bleaching, the world’s largest coral reef ecosystem, parts of the Great Barrier Reef in Queensland, Australia, are estimated to have lost two-thirds of their corals, mainly in the northern section.

In 2009, Dr Charlie Veron, known globally as the Godfather of Coral, gave a lecture at the Royal Society called ‘Is the Great Barrier Reef on Death Row?’. That was eight years ago and, currently, Veron’s Facebook page says: “Coal mining is the number one danger to coral reefs.”

Controversy continues as to whether a giant coal mine should be built in Queensland. The Carmichael or Adani coal mine would be the largest in Australia, adding a significant contribution to greenhouse gases. Transporting the coal to India would also involve enlarging the Queensland port, which would involve dredging – i.e. blocking sunlight and starving corals – not to mention potential water pollution through shipping. The Australian government argues that the new coal mine, which is supposed to provide cleaner coal, will have strict checks and balances and it will hugely stimulate local employment.

While governments move slowly, scientists are snapping into action. Can their technologies save the Great Barrier Reef?

Dr Matt Dunbabin is a roboticist at Queensland University of Technology. He is also principal research fellow of autonomous systems at the university’s Institute for Future Environments. Dunbabin specialises in field robotics and their application, particularly in marine and aquatic systems. His prototype for a ‘Robo Reef Protector’ won funding from Google as part of its Impact Challenge Australia in 2016.

He says he first had the idea in 2005, but it would take another decade for the technology to catch up. Dunbabin calls this “a number of advances converging”: advanced machine learning techniques (i.e. artificial intelligence), small enough GPUs and a biological means to control the coral-eating crown-of-thorns starfish. The latter is done by administering a fatal dose of bile salts.

The RangerBot, to give it its proper title, is being field-tested so the design may yet be refined. However, five RangerBots have been built. What we have is a seeing AUV (autonomous underwater vehicle) designed, in Dunbabin’s words, to do three key things: “Estimate our position underwater; obstacle detection and avoidance, both day and night; and real-time seabed classification including crown-of-thorns starfish.”  

The multi-function Bot will have a water-quality probe, a water sampler and a sediment collection device. Meanwhile, the crew can watch the action aboard a 15W embedded computer.

The starfish are particularly dangerous when there are more than about 15 of them per hectare, according to the GBR Marine Park Authority. This happens when increased nutrients coincide with breeding season and, predictably, when there are fewer predators.

The Bots have been tested at various locations around the Great Barrier Reef. During one test, the aftermath of a cyclone proved useful as Dunbabin and his team had to adapt the Bot to deal with reduced visibility conditions. It also had to be able to see in artificial light at night.

So just how useful does Dunbabin envisage the Bots will be? “You can never out-compete a human for the complex hand-eye coordination tasks that divers do,” he says, “but they can spend a lot more time in the water and in water with crocodiles and sharks. With large enough numbers we will definitely make an impact at reef scale.”

It has been estimated that six Bots could cover the Great Barrier Reef about 14 times a year, whereas six human divers could cover only half of it.

Dunbabin explains the final goal: to put this technology in the hands of community groups who don’t spend a lot of time along the length of the Great Barrier Reef. They will then get “early warning of threats, understand where intervention is required, and increase the rate at which interventions can be administered”.

What does Dunbabin think of Dr Veron’s prediction?  

“Limiting our impact on the Great Barrier Reef requires the world reducing greenhouse emissions and global warming. I have seen areas that have been hit hard with the combined impacts of crown-of-thorns starfish, cyclones and coral bleaching, but I have also seen beautiful reef sections from the south to the north. This gives me hope.”

Another approach is to try and block out the sun with clouds or surface films.

Professor David Solomon is a polymer chemist who co-invented the polymer banknote. On this project, he has been senior scientific advisor to Professor Greg Qiao at the University of Melbourne and, together with Dr Joel Scofield and Dr Emma Prime, they have developed a film that sits on water to block sunlight.

After discussing  the Great Barrier Reef’s plight with AIMS (the Australian Institute of Marine Science), they saw an opportunity to use “surface films as a way to help spread particles which would be able to scatter light ... we then worked closely with AIMS to develop an optimised film which would achieve reductions in light intensity while being environmentally friendly”.

Solomon says all the materials used are naturally occurring, including the main one – calcium carbonate. “This small organic molecule assists in spreading the particles which are key for reducing the light intensity that the corals are exposed to.” It is what coral uses to build its skeleton and is also present in sea shells and sand.

The films are very thin and Solomon is not aware of any adverse affects: “If the film is disturbed due to marine life, it is able to re-form. The field trials we conducted last year showed that the films do not negatively impact the corals.”

The sunshield has only been trialled in small, at-risk areas during bleaching. The group aims to keep testing.

Dr Daniel Harrison is a former civil engineer turned oceanographer based at Sydney University’s Marine Studies Institute. In 2017, he became a Myer Innovation Fellow for his work on preventing coral bleaching by brightening marine clouds – brighter clouds reflect more sunlight into space, thus cooling the reefs below.

The idea came about when he was looking at potential engineering interventions that might be able to help cool the waters of the Great Barrier Reef. He was aware of solar radiation techniques for geo-engineering from his PhD work on ocean fertilisation, and also of research suggesting that there was a link between sea surface temperatures in the Great Barrier Reef and cloud cover. “Corals bleach from a combination of both sunlight exposure and high water temperatures ... if you shade the corals from sunlight, they can withstand a much higher water temperature.”

So what is the process of cloud brightening?

“Over the oceans, the concentration of cloud droplets is often limited by the number of aerosols available to form cloud condensation nuclei. So when clouds form, the clean air causes the moisture to condense onto fewer nuclei, which results in fewer large droplets for a given amount of moisture in the cloud. A cloud with large droplets reflects less shortwave radiation than one composed of smaller droplets and is also more likely to rain and dissipate, thus overall it reflects less energy back into space,” Dr Harrison says.

And now comes the part where the scientists intervene: “The process of marine cloud brightening aims to provide additional aerosols in the form of nano-sized sea-salt crystals derived from seawater, and to inject these into the atmospheric boundary layer above the ocean. The boundary layer interacts with low-lying marine stratocumulus clouds, which are some of the most effective at cooling the planet.

“The sea salt aerosols are also very reflective and reflect some shortwave radiation back into space themselves. Overall, the albedo of marine clouds depends on the concentration of aerosols.”

How big an impact could cloud brightening have in cutting the loss of atmospheric aerosols? Dr Harrison has been working with the Reef Restoration and Adaption Program (RRAP), led by the Australian Institute of Marine Science. “Scientists are looking into how the reef brightens clouds by producing its own aerosols formed by a chemical reaction in the atmosphere, of dimethyl sulphide (DMS) gas, which the corals produce.”

He is concerned that lost coral cover on the Great Barrier Reef will also mean losing a potentially important source of atmospheric aerosols. This may affect the regional climate of north-east Australia.

Another possible solution is to re-generate the coral itself either by transplanting it or by breeding its resistance. The technical terms for this are ‘larval re-seeding’ and ‘assisted gene flow’, respectively.

Professor Peter Harrison and a team at Southern Cross University have successfully trialled larval re-seeding (that is harvesting coral eggs and sperm during the coral spawn season, growing the coral larvae in laboratory tanks, and then re-seeding it on reefs in the Philippines and on the Great Barrier Reef to re-establish breeding populations.

Dr Ken Anthony, a principal research scientist at the Australian government’s Australian Institute of Marine Science, is the lead author of an article that argues that more extreme measures – such as experimenting with moving coral that has already adapted to higher temperatures to cooler areas (assisted gene flow) and trying to produce tougher coral species through selective breeding (assisted evolution) – may be necessary.

However, transplanting reefs globally could cost trillions of dollars. The Great Barrier Reef alone is over one thousand miles long.

So what does the Godfather of Coral himself, Dr Charlie Veron, think of all of the above?

He thinks that coral re-seeding has the potential to make an impact by helping to discover what makes heat-resistant coral heat-resistant. But “crown-of-thorns starfish are rare on most of the Geat Barrier Reef at the moment”, he says. “You are talking about ‘coral gardening’ in an area the size of Italy and that’s only the Great Barrier Reef.”

Yet, Veron says, hope is essential, too. If the unthinkable occurs – if these rainforests of the sea die, more than a million marine species may go with them. And we humans will suffer, too – there will be flooding, coastal erosion, and loss of fishing and tourism. Scientists can work against the clock and come up with stop-gaps, but it is unlikely they can beat the steady progress of emissions.

As Professor Ove Hoegh-Guldberg, a marine biologist and director of the University of Queensland’s Global Change Institute, told the Guardian: “The only economic way to deal with this issue is to reduce emissions and take up renewable energies at a furious rate.”

Does Sydney University’s Dr Harrison agree with Veron that coal mining is the number one issue that needs to be solved?

“We have a very short amount of time now to act to save the world’s coral reefs,” he says. “In just 10 years’ time, the average global temperature will be around that of the 2015/2016 El Nino, which caused severe bleaching to around two-thirds of the Great Barrier Reef. Combined with the bleaching the following year, up to 50 per cent of shallow-water corals in the GBR have been lost.”

While drastic global reduction in greenhouse gas emissions remains the most critical action, other active interventions are also necessary. “The oceans are warming too fast for the world’s coral reefs to adapt and further temperature increase is already ‘locked in’,” explains Dr Harrison.

“If we are unable to garner even the political will to deal with the low-hanging fruit of coal-fired power, then I believe we are forcing ourselves into a corner where ultimately we will need global geo-engineering in order to preserve our way of life and mitigate against collapse of many important ecosystems, including coral reefs.”

Can Dr Harrison imagine a world without reefs?

“Covering less than 0.1 per cent of the ocean surface, but providing up to 25 per cent of all marine life with habitat ... it is hard to overstate how important coral reefs are to the health of the oceans. A world without coral reefs is a very real risk given the unwillingness of governments and society to make the changes necessary to limit global temperature increase.”

Alarm bells should be going into overdrive. As Dr Harrison says: “Coral reefs are the canary in the gold mine; if we lose the world’s coral reefs, what will be next?”