Engineering a rescue for the Great Barrier Reef, one of the world’s iconic natural wonders. Stuart Nathan reports

The Great Barrier Reef is unquestionably a wonder of the world. The largest coral system on Earth, it consists of more than 2,900 individual reefs and stretches over 2,300km (1,400 miles). Famously visible from space, it represents one of the most biodiverse known habitats and is of huge importance to the Australian economy, both because of tourism and because it supports fisheries. Moreover, the reef is of huge cultural significance for many Pacific communities. And it is in trouble.
The biggest threat to the reef is coral bleaching. This is caused by rising sea temperatures, and as a result of the complex nature of coral. Within the tissues of the millions of living creatures that comprise coral are microscopic, plant-like organisms called zooxanthellae, which capture sunlight, convert it to energy, and provide nutrients to the coral.
However, if sea temperatures rise, the coral expels the zooxanthellae and loses its colour. This doesn’t kill the coral straight away, but bleached coral is effectively starving and, if conditions do not return to those hospitable to zooxanthellae, it will die. Researchers in Australia are now trying to find ways to help corals in the Great Barrier Reef resist higher temperatures without bleaching, which they hope will preserve this unique environment.
Although it’s a world away from the factories, medicines and synthetic materials that characterise engineering in much of the world, this effort is nonetheless engineering of an important kind.
Coral bleaching is a natural event, and research indicates that bleaching has occurred many times during the reef’s existence. But extreme heat waves in 2016 and 2017 affected up to two thirds of the reef, and current extreme temperatures are likely to have similar consequences. However, other reefs can withstand conditions in warmer waters: the Red Sea is consistently warmer than the seas around the Great Barrier Reef, for example.
Dutch researcher Madeleine van Oppen of the Australian Institute of Marine Sciences in Townsville, Queensland, visited London last year to talk about her work in engineering hardier coral. Van Oppen’s work focuses on two techniques: assisted gene flow and assisted evolution. The first of these works by moving warmth-adapted corals to cooler parts of the reef; the northern extreme of the reef is routinely 1°C to 2°C warmer than the southern portion in summer. Corals are mobile in their larval form but, under normal conditions, larvae from the north do not travel south because the main ocean current that flows across the Pacific splits off the coast of northern Queensland, and flows are not favourable to north-south transfer. The researchers are experimenting with manually moving some of the northern corals south. If enough corals were moved, it could help heat-damaged reefs recover faster.
Assisted evolution is a somewhat more complex technique, which van Oppen described in a paper published in the Proceedings of the National Academy of Sciences in 2015 and in Nature Ecology and Evolution in 2017. “It’s artificial selection on steroids,” she said. Targeting both the coral host and its symbiotic zooxanthellae, it takes several different tacks to improving their resistance to stress, in this case from heat.
One way to do this is by a technique called stress conditioning. This involves exposing coral to heat levels that approach those that will cause bleaching, and to investigate, firstly, whether the coral can adapt to this and, secondly, whether it can pass those adaptations to further generations. Evidence for this exists in some plants and animals, but it is not yet known whether coral can be stress-conditioned. Van Oppen and her colleagues are looking at this technique in the National Sea Simulator (SeaSim), a marine research aquarium in Townsville, which can store more than 3.5 million litres of seawater and can carry out spawning experiments on many reef organisms simultaneously and over several generations.

Another approach is more typical to genetic engineering, involving creating hybrids by bringing together compatible eggs and sperm from different coral species. This is known to occur naturally in some types of coral, increasing genetic diversity and producing novel genetic combinations that may be useful in selective breeding. “It’s quite rare in nature, but not difficult to do under laboratory conditions,” van Oppen said. Working at SeaSim, the researchers are looking to hybridise multiple pairs of coral species during their annual spawning (a major and predictable event) and grow their young under controlled conditions to select for climate resilience, then crossbreeding strains to produce desired results exactly the same way that conventional husbandry has worked for many centuries in agriculture. Hardy specimens could then be transferred to the reef itself.
Yet another approach is one that is sometimes used in humans to give health benefits: probiotics. These are live organisms, generally bacteria, which can confer beneficial effects if they establish colonies inside their hosts. Coral contains several potential habitats where probiotic colonies could be established, including the layer of mucus that coats its surface, digestive systems and even its mineral skeletons. Van Oppen and colleagues, including Katarina Damjanovic, are trying to develop probiotics that could either help coral tolerate the heat better, or help it recover faster from bleaching events by creating a more hospitable environment for the essential zooxanthellae. “One thing that probiotics could do is mop up oxygen radicals that occur in water and are damaging to the living coral tissue,” van Oppen said. “One big advantage of this approach is that we could administer the probiotic anywhere on the reef.”
Van Oppen is open about the potential for these techniques. “Our big hope is that it can buy us enough time to tackle the warming without the reef dying in the meantime. She also admits that, even if the technique was successful, it would change the Great Barrier Reef significantly. “At the moment we have a very diverse reef, with many different coral species,” she said. “We are not going to be able to create successful strategies for all of those species, so even if successful, we will have a much less diverse reef. We simply don’t know what the consequences of that for other life might be.
“If the reef rejects the results of our experiments, the effort will be wasted.” However, she adds: “The risk of doing nothing is just far too great.”
Thank you for covering this work – every bit as important as sticking rockets into space or breaking speed records. I wish this team all the luck in the world in their endeavours, but fear that we as a species are doing far too little far too late. Only idiots now argue that the planet is not warming, or that we (being the clever things that we are) will simply manage to find a solution to all of the world’s problems in the nick if time! I have grand kids now – I fear for their future given the ever deteriorating state of things now ….. but welcome the efforts of those who are trying to make a difference!
Have visited once: what a wonderful place. And how delightful that at last, work and effort to retain this remarkable asset is in hand and prospect. I believe we (ascent of man) know more about the surface of the moon than the underseas areas of 95% of our planet. How silly.
The comments about how little we know of the oceans have reminded me that the ocean discovery X-Prize is coming to a finale at the end of march. Somewhat unrelated I know, but with a British interest hopefully we will see an article on it soon
https://www.xprize.org/prizes/ocean-discovery
Siberian scientists managed to domesticate silver foxes within 8 generations, so hopeful that assisted evolution may be successful ( accepted foxes not same as corals and the researchers give examples in the (2015) PNAS link that had varying levels of success). It seems that the researchers have a good grasp of the laws of unintended consequences and I think this effort may prove the first case of geo/environmental engineering activity to save something of the ecosystem even if biodiversity may be affected, as they themselves recognize. Nonetheless, it is a very worthy cause and the risks may be manageable. One suggestion to add to the coral nurseries they mention is to add a ‘small’ number of temperature and acidity controlled nurseries to retain as much of the current stock of corals for later release if and when climate can be stabilized and restored (coral ark or zoo, so to speak) – otherwise I wish Mss Van Oppen, Putnam & Gates and Mr.Oliver the very best and hope that their efforts of 2015 continue to be supported with urgency.
Frank,
“when climate can be stabilized and restored”
What an arrogant statement; earth has been controlling its climate for ~4.5 billion years, we have been here just ~250,000 yrs.
We don’t control the climate, we are the product of the climate; study geology and discover how wide ranging earths climates can be.
We are an opportunist transient creature that developed in a set of natural climatic circumstances, just like the millions of extinct species that came before us & the millions that will follow us when we’ve gone.
When we’ve learned how to control – planetary gravitational effects, Hadley cells, sunspots, solar flares, Milancovich cycles, plate tectonics, volcanoes , clouds…
then we can have a go at controlling the climate.
Hello saveenery ! I am sorry if that statement appeared arrogant, perhaps I shpuld have worded it differently. I did not intend to imply humanity would actively geoengineer the climate, only that we can restrain ourselves sufficiently to allow the climate to stabilize itself to what the local biota can thrive in – where the article was particularly about the great barrier reef as it is now, then that local biosphere is what I had in mind. Otherwise I am in full agreement with you – I think James Lovelock called Gaia a ‘tough Bitch’ who can take care of herself ok over geological timescales – the problem is ours if we intend to survive it. ( and judging by the latest fiasco over port maintenance dredging being approved for dumping into the GBR, we cant be too hopeful). Regards