Welcome everyone to 100 Climate Conversations and thank you for joining us. I’d like to acknowledge the Traditional Custodians of the ancestral homelands on which we meet today, the Gadigal people of the Eora Nation. We respect their Elders, past, present and future and recognise their continuous connection to Country.

Today is number 53 of 100 conversations happening every Friday. The series presents 100 visionary Australians that are taking positive action to respond to the most critical issue of our time, which is climate change. We’re recording live today in the Boiler Hall of the Powerhouse museum. Before it was home to the museum, it was the Ultimo Power Station. Built in 1899, it supplied coal powered electricity to Sydney’s tram system right up until the 60s. In the context of this architectural artefact, we shift our focus forward to the innovations of the net zero revolution.
My name is Paddy Manning, I’m a journalist and author, most recently of a biography of Lachlan Murdoch called The Succession. But I’ve also written extensively on climate change. And sitting next to me is Madeleine Van Oppen who I have the pleasure of speaking with today. Madeleine Van Oppen was trained as a marine ecologist and became a geneticist and expert in microbial symbioses of corals. Her current research focuses on assisted evolution, the development of corals that are better able to cope with disturbed environments and predicted future ocean conditions. This includes the development of bacterial probiotics, the directed evolution of the corals, microalgal symbionts, and we’ll get to explaining all these terms. And coral hybridisation, selective breeding and coral conditioning. We’ve got a lot to talk about. We are so thrilled to have her join us today. Please join me in welcoming Madeleine.

We’ll start at the easy stuff. You grew up in Holland, not known for its coral reefs. But like many of us, you were inspired by Jacques Cousteau. Can you tell us a bit about your upbringing and how you became a marine ecologist?

Yes. So, I grew up in a small village in the south of the Netherlands. A landlocked village. No ocean nearby. I did watch the Jacques Cousteau documentaries and was inspired by them. And when I finished high school, I went to university to study biology. But I loved all aspects of biology, and I found it really difficult to choose where to specialise. So, the funny thing was, where I lived as a student, I would walk past the head office of the Dutch on the Water Society every day. And, you know, it made me think about Jacques Cousteau. And I wasn’t a scuba diver at the time, but it made me realise that what I wanted to do was to become a marine biologist. And so, I had to change university. I had to go to the north of the Netherlands, which isn’t far, of course, because it’s such a tiny country. And I completed my degree in marine biology there.

Your first experience, I understand, of diving on coral reefs was in the Red Sea, and you describe the experience as overwhelming.

Yes, I was very lucky to travel a lot during my studies. I did a master’s project on Bonaire in the Dutch Antilles. That was actually my first experience with coral reefs. But I wasn’t working on corals. I was working on parrotfish. They eat coral skeletons, so they are important for the calcium budget on the reef. So we were studying those. And then when I was doing my PhD, I did a trip to the Red Sea that was – in those days dive safaris became popular in Egypt. And so I did one of those, and it was absolutely amazing. I mean, the colour and the diversity and even the landscape in the Red Sea, it just blew me away. And then the next experience was the Great Barrier Reef, which is, of course, also fabulous. The Lake Malawi Research. Well, there’s no corals in Lake Malawi. It’s a freshwater lake. But I was working on Cichlid fishes and Cichlid fishes are known for their rapid speciation. Huge radiation has occurred in these lakes. And I was studying what some of the genetic and some of the processes [were] that may be responsible for that fast rate of speciation in these fishes.

Some of your earliest research was on cold water seaweeds, and I understand that’s what brought you to Australia and New Zealand, [when] you went to Victoria. What were you studying there?

So, when I finished my master’s and decided I wanted to do a PhD, I wanted to learn more about genetics, because as I said, it wasn’t a big component of my undergraduate degree. But I had realised I had sort of done a little research project also during my master’s using genetics, and I could see the power of genetic tools in answering ecological and evolutionary questions. So, I looked for a PhD project that allowed me to do that. And so, I worked with cold water seaweeds. And I used DNA sequencing to study how seaweeds had distributed themselves across the world over evolutionary time, how the last ice ages had influenced their evolution and distribution. And so, it gave me a real good basis in ecological and evolutionary genetics.

During my PhD because I was working – one question that I was working on is how some species of seaweeds occur in the North and South Pole in the temperate to polar regions, but not in-between. And one question is how did that distribution originate? And when I started my PhD, there were a lot of samples in the lab already, but not that many from the southern hemisphere.

So, my PhD supervisor sent me to the south of Australia and south of New Zealand to collect some additional samples, which was absolutely wonderful, was my first trip to Australia. But other people in my lab were working on tropical species and they said, ‘Can you please go to Townsville and collect this and that?’ And I said, ‘Of course.’ And that is how I made some connections with people at the university there and people at AIMS, the Australian Institute of Marine Science. And it turned out that they were using very similar genetic approaches to study corals to the ones that I was using on seaweeds. And so, I kept in touch with the people at the university and that’s how I eventually got my first position in Australia a few years later.

Wasn’t long after you came here, as I understand, that we had the first mass bleaching event in 1998 of coral reefs around the world. Can you explain to us where you were at that time and then also how that changed your research?

I came to Australia in 1997, June 1997. I will not forget because I was pregnant with my son who was born in December of that year when we were going into the first major bleaching event on the Great Barrier Reef, which happened in early 1998.

To understand what bleaching is, you first need to realise that corals form a very intimate relationship with microalgae. They live – the microalgae lives inside the coral cells, and the corals rely on these microalgae for most of their nutrition. So, the microalgae use energy from the sun, and they turn carbon dioxide and water into a number of compounds, including sugars. And they then release a lot of those sugars to the coral cells. So, they translocate from their own cells to the coral. And the corals rely on that nutrition. They can also feed what we call heterotrophically, and they can capture a little sort of plankton animals, but they mostly rely on the sugars that they get from the microalgae.

And so that’s what we call a symbiotic relationship –

That’s right –

Between the algae in the coral?

Yes.

And so, the algae is the symbiont, which is the first big word that we heard earlier.

That’s right, yes. So, the microalgal symbionts – and when the coral reaches the symbionts, the microalgae are lost from the coral tissues and now as microalgae they have sort of a golden-brown colour and they give the coral their main colour. Most corals are brown and then they have some maybe pinks and blues and yellows, which are caused – they are caused by pigments that the coral makes itself. But the brown colouration is due to the microalgal symbionts. And when the corals loses these microalgae, all of a sudden we can see the calcium carbonate skeleton through the coral tissue, which itself is translucent and that is why it’s – so bleaching is a paling of the coral – and that’s why we call it coral bleaching.

And is it dead?

A coral can recover from bleaching if it can regain the microalgae. But if the stress – like the heat during a summer heatwave, we often see mass bleaching events – if that lasts for too long, the coral was staff and die before it can recover. So, it depends on how extreme and intense that stress event, that heat wave actually is, whether it will die or whether it will survive.

And so, the scientific community in 1998 is shocked, horrified at the scale of the bleaching, would that be right?

Absolutely. It was really the first global mass bleaching event. I mean, there had been sort of small-scale bleaching event, a more regional, maybe slightly larger bleaching events, but 1997, 1998 was the first global mass bleaching event. And I think that’s when it really hit home that climate change is really here and it’s going to have a major impact on coral reefs. I started working on corals when I came to Australia in ’97 and then towards the end, maybe ’99, 2000, I started to focus on those microalgae that have this intimate relationship with the coral. And there was some sort of research starting to come out that suggested that this algae may actually be playing an important role in bleaching and in the upper heat or temperature tolerance limits of corals. So, I started to describe the diversity of the microalgae on the Great Barrier Reef and starting to tease out what the function might be within the coral animal.

So, the first project I worked on when I came to Australia was understanding the evolutionary history of reef building corals. And I discovered – and this supported a hypothesis that Charlie Veron had postulated years before, but using genetics, I could demonstrate that over evolutionary time corals hybridised meaning that different species crossbreed and produce offspring that then survives on the reef. And we could see that in our genetic data. And on the Great Barrier Reef, where we have high coral species diversity, it’s a little complex to sort of decipher that. But in the Caribbean, there’s diversity of corals as well. But in a particular group of corals, the acropora corals, there’s only two coral species. And then a third one, which turns out to be a hybrid as well. So, that’s a simple system. And I did a little bit of work on that one as well to understand that.

Data from colleagues from the Caribbean showed that the hybrids in the Caribbean, this actually used to be quite rare, but it’s increasing in distribution, and it sometimes is actually more tolerant than the two parent species. And that made me think, well, can we use hybridisation to increase tolerance of corals as a as an intervention and a restoration method? So, this discovery that hybridisation occurred in Great Barrier Reef corals and then comparing it to the Caribbean situation made me then think of can we harnessed these naturally occurring processes.

Your discovery triggered worldwide headlines at the time. What was the light bulb moment? How did it happen?

Yes, I think it probably wasn’t a eureka moment, it was probably more gradual. Because for decades I was studying how corals adapt to environmental change and then the realisations, as I just described about the hybridisation, but also when we discovered that some microalgal species made corals more heat tolerant than others and then we started to actually manipulate those symbioses in the lab just to understand the role of the microalgal symbiont and not just to make hardier corals. It just made me think, well, why don’t we take it a step further and not just try and understand mechanisms but try to utilise those mechanisms to help corals cope with climate change better.

Was it a straight line from the discovery of crossbreeding in corals to the idea of human assisted evolution? And can you explain to us then what is human assisted evolution in corals?

So, human assisted evolution is pretty much us intervening with natural processes, but not changing those natural processes, but taking those and speeding them up mostly in the laboratory, but eventually also on the reef. So, it’s the acceleration of natural processes that already happen out on the reef to speed up the adaptation of corals, so they become tolerant quicker.

And if we fast forward a decade, the landmark 2015 paper for the Proceedings of the National Academy of Sciences, you argued it was, quote, ‘prudent to explore the potential to augment the capacity of reef organisms to tolerate stress and to facilitate recovery after disturbances.’ How was that paper received?

Yes, I was asked whether I’m playing God many, many, many times. Yes, a lot of scepticism and resistance even from within the scientific community surprisingly. It’s interesting there was – an international coral reef meeting occurs once every four years, and there was one in 2016. And just recently I was talking to a colleague, and I said, ‘I remember vividly, everybody was talking about it,’ and I realised mostly behind my back. And people just were worried, and they thought it was crazy. So, there was a lot of resistance.

You weren’t put off?

No, I wasn’t put off because I thought it was a strange argument to say I’m playing God. We have already influenced the marine environment as we have to the terrestrial environment. I mean, in fact, there’s nowhere in the ocean where we cannot measure human influence. So, to say that we’re playing God by trying to repair some of the damage that we’ve done, I thought that was very strange. I think to some extent, the marine environment is something more foreign to the general public, not to marine scientists, obviously. And maybe that’s why people feel a little bit more hesitant about intervening with that environment, because if we look at how we live here in the city, which part hasn’t been modified by humans? Everything has been modified by humans and we accept that quite readily. But when it comes to the marine environment, all of a sudden people are a little bit more hesitant. And I suspect that to some extent that’s because it’s more foreign to a lot of people.

Your paper described a number of different approaches to assisted evolution and each represented incrementally more human intervention. Can you explain those different types just in broad terms?

So, one is what we call conditioning. And people might know that from agricultural species where people talk about hardening. It’s pretty much a different word for the same thing, where you expose an organism to stress, but stress that doesn’t kill it. And so, it’s sort of, if it doesn’t kill you, it makes you stronger and that can happen. So, we’re exploring whether mild stress can actually preset corals to cope better with subsequent heat waves. So, that will be a relatively low risk on the on the scale of risk, a low-risk intervention. But I should say, so far researchers have found that, yes, sometimes it does actually increase tolerance, but not always. Actually, sometimes it has a negative effect, so, it could have negative impact. Another one is the selective breeding. We use two different approaches. One was where we cross different species and that comes back to that earlier research that we spoke about –

Hybridisation?

Hybridisation, yes, between species. So, you have to understand, if you have different species that evolve separately, for most of the time, their genomes are going to diverge. You know, random changes happen in genomes just because every cell division, the cell machinery that copies the chromosomes makes mistakes and mutations will occur and some will maintain. So, then when you bring those species together, if you can still crossbreed them, you bring that diversity together in the offspring in one organism. So, you increase genetic diversity and also you make a different gene combination in the hybrid offspring. And sometimes the combination of these different genes results in different characteristics of that offspring. And it could be that it’s more tolerant to heat, could be more resistant to disease, it could have negative impact and some hybrids as well. So, that’s one approach that we have been testing.

And the other one is also a form of hybridisation, but within species. And here we select the broodstock, the parents, based on their relative heat tolerance. So, we breed parents that have high heat tolerance and then to create a lot of offspring that also has relatively high tolerance and that can be beneficial in terms of restoring coral reefs with offspring that has a little bit more heat tolerance. And then another approach is where we manipulate microbes that associate with corals, and that includes the microalgae that we already spoke about because we know now that they play a very important role in the upper heat tolerance limits of the corals. And so, we know that certain species of microalgae that occur naturally on the reef give the corals better tolerance than others.

But we’ve also known that in many instances that comes at a cost of slower growth to the coral because those algae translocate less sugar to the corals. So, there’s a trade-off with – an energetic trade-off between heat tolerance and growth and also reproduction, because that costs a lot of energy. And so, what we can do, a lot of these algae we can take out of the coral and we can culture them in the lab. And in the lab, we can speed up the rate of adaptation and we can adapt them to increasing temperatures. And we’ve done that and then we’ve reintroduced them into coral and it’s actually quite exciting.

We’ve now been able to evolve a microalgae that has high heat tolerance, but it doesn’t come with that trade off, as we call it, for growth. So, it still gives the coral a lot of sugars and that’s really exciting to us. We’ve tested that in the lab, and we’ve just deployed some corals that were infected with this heat evolved algae in the field to see how the coral will perform in the field as well. So, that’s pretty exciting. And then the last one is where we manipulate bacteria that associate with corals. Just like ourselves we have a very diverse gut microbiome. Which is really important for our health, our function, even our state of mind. Mental health and many, many characteristics of humans. So, corals similarly associated with bacteria that occur on the surface of the corals, also inside the coral tissues in the gut, pretty much everywhere in the coral. And so, we are exploring whether we can develop a bacterial probiotic, if you will, that might help the coral in the summer heat waves.

When you’re actually doing this selective breeding, you have to take advantage of a single moment, a spawning event of the corals when they reproduce. Can you describe that to us? Because I’ve got a picture from some of the things, I’ve read a bunch of scientists in a lab watching coral spawn, carrying buckets around and doing it all by hand. It all sounds very rarefied, but it’s actually high-pressure hands on, isn’t it?

It is. Most coral spawn once a year, so one shot pretty much we got at doing this sort of work during the coral mass spawning event as we call it. So, the way that works is that we go out to the reef, and we check whether they are likely to what we call spawn, which is the release of their sperm and eggs. We can just break off a little fragment just before they spawn a few days before, and the eggs that are inside the polyps become coloured pink or red. And so you can actually see that –

Visible?

Visible, yes to the naked eyes. Well, maybe not now I need reading glasses, but when you’re younger, you can see it on the water. And so, we bring them in and then we now can predict pretty accurately when they will spawn. So, on the night of spawning, we isolate the colonies, and we watch them and then when they release, they release bundles of sperm and eggs that will float to the surface, and we can collect them. In sort of the early days we would scoop them up with a with a beaker or something like that, pretty low tech and then we can separate the sperm from the egg.

So you do that by hand?

We do. Well, yes, we do it by hand. And this is in the R&D phase, once you scale it up it all has to be automated. But yes, by hand initially. So, we have a simple piece of PVC pipe and we put a – we glue a mesh to the bottom. And we then have a plastic bowl with some seawater and then we pour the bundles of sperm and eggs on top. And then we just gently agitate it, and the sperm will go through the mesh and the eggs will stay on top and then we can take the eggs out. And so, we have the eggs and sperm separated, and then we can set up any sort of invitro cross that we want.

So, you can take those eggs from one species and carry them over to another space and they’ll hopefully reproduce.

Yes. And not all species will cross fertilise, but some do.

What’s the point of all this – are you trying to build a better reef or breed super corals, or is that a bit of a misnomer?

Yeah, super coral is a misnomer because any trait that you select for by whatever method – the microbes or selective breeding – is likely to come at a cost to other characteristics. Because within an organism there’s only so much energy to go around. So, if you change it so that it can sort of invest more energy in coping with heat, it will likely come at a cost of something else. So, that’s why the word super coral in the scientific world, we don’t really like it because the super coral doesn’t really exist, but we’re trying to improve the traits that we feel are critically important for corals to survive the next few decades until we actually deal with climate warming.

And why do we need to save reefs? Is it just to save the pretty corals? There’s a whole kind of food chain that depends on corals, isn’t there?

Yes, exactly right. Yes. Reefs are home to about a third of all marine species. So, if you lose reefs, you lose most of those species and that has consequences as well for other marine ecosystems, but also for our own economy. I mean, some countries or peoples depend on coral reefs for their livelihood, some of the Pacific Islanders, for instance. But even for a country like Australia, the Great Barrier Reef has huge economic value and those important industries that it supports, fisheries, pharmaceuticals, tourism. It provides a lot of jobs, but it also has very important spiritual and cultural values, particularly to Traditional Owners of the reef.

So, if you lose reefs, it’s a disaster I’d say. I mean, they also protect Queensland coastline, the Great Barrier Reef, the coral. So, when we lose the Great Barrier Reef, there will be far more erosion on top of sea level rise. That’s going to be quite disastrous, I think.

Is the solution scalable? It’s a fundamental problem with everything to do with the Great Barrier Reef, isn’t it the size of it? I mean, people describe it as the canary in the coal mine, but it’s the size of Italy. How do you scale up this assisted evolution?

Yes, it’s a difficult question and it’s a huge challenge. I think to some extent we can be strategic as to where we put out those enhanced corals. Now we know that we call connectivity on the reefs. So, the connection between reefs based on ocean currents is not the same for every reef. Some reefs would receive a lot of propagules and others would be more like a donor reef. So, we could think of maybe restoring donor reefs. So, maybe naturally some of these enhanced corals will spread over the generation.

If we succeed in any enhancement via the microbes that associate with corals, I think that will provide a lot of scope to address the scale because you can think about those microbes will also establish likely establishing in the environment. So, they might be able then to associate with other corals. But there’s a lot of unknowns still, and this is one of the major research areas that we’re working on. How can we do this at a scale that is relevant? Well, I want to say that even if we feel it’s difficult and we don’t know the answer completely today, technological developments happen so fast. What is not possible today might be quite feasible five years down the track. So, I don’t think it should stop us developing these interventions if we don’t fully understand yet how we can implement at a scale that is relevant to the issue.

You can’t help every coral species adapt, can you? Given the incredible diversity of just even the Great Barrier Reef, how do you decide which corals to breed and what a healthier reef might look like? Do you want to save every single species or just a representative sample?

In an ideal world, we would want to save every species. But in reality, if we’re talking about enhancing corals, I don’t think that will be feasible. Just resource wise, that’s going to be impossible. So, we have to make decisions as to which species we’re going to select. And again, that’s a difficult question.

So, we sat together as a group of scientists and brainstormed as to how we could best do that, and we went through some thinking processes. First of all, can we identify the function that different coral species provide to the reef? And that is very difficult because we don’t know enough about many corals. We know something about a small number of coral species, but we know very little about many other species.

So, what we proposed – and this paper is hopefully going to come out soon – is that we just look at what we call this trade space. So, every coral is different, it has different characteristics, and you can plot that into the trade space. And so, if we pick corals for restoration that cover a large area of that trade space, then they probably have – we feel they have the best chance to be able to cope with any environmental change, even if we cannot predict everything in the greatest detail. So, it’s sort of a bet hedging strategy. We think that that might be the best strategy. It still needs to be peer reviewed by the wider community once the paper comes out. But as a subset of coral reef scientists, that’s what we are going to propose.

Earlier in this series, we heard from Charlie Veron. He’s named half or a third of the coral species on the reef. He said it’s already 95 per cent gone compared to what he first saw when he dove at the Great Barrier Reef as a young man. How much can you save?

I think we should make an effort in also setting up biobanks, and Charlie is involved in one initiative where the biobank will consist of large-scale aquaria to keep corals alive. And I think they call it Noah’s Ark, or he’s referred to it as such, where they collect a number of individuals of all the species on the reef. Other researchers are developing cryopreservation techniques and we can already cryopreserve coral sperm quite well so that’s –

You’re doing that in Dubbo, aren’t you?

I’ve been involved in some of the early work, and we actually established the first Great Barrier Reef coral sperm bank and that’s housed in Dubbo, Tarogna Conservation Society. So, the cryo people are now also – they’ve had some successes where they can preserve little pieces of coral tissue even with the microalgae inside. And that would be wonderful if you can just thaw that out and it grows into a coral. And they’re also trying to develop technologies to preserve coral eggs.

And I see that as an analogue to seed banks, that people who work with crop species have developed over the decades and now they are sort of tapping into the seed banks, sometimes also to cross plants originally from different regions in the world where they had to adapt to different environments and to just create diversity in the pool of the individuals in the crop and give them the best chance to cope with climate change. And I think we should do something similar for corals, be it cryopreservation or in an aquarium. And there’s also initiatives for people identifying regions in the world where corals might survive better. Actually, in the field and those could maybe receive high conservation status. So, there’s different approaches that I think should be done at the same time to preserve as much as we have left today.

Because it’s not just the warming that we’ve seen so far, is it? There’s a lagged effect, as I understand it, which is even greater in the oceans than the atmosphere, for example. And so, the oceans are going to continue to warm for centuries, even if we stop emitting greenhouse gases tomorrow.

Yes, I’m not a climate scientist, but what I understand from the literature is that even if we stopped all greenhouse gas emissions today, there would still be further warming for some period of time. And that lag effect of these gases in the atmosphere, that will continue for some time. And that is, of course, a great worry. So, we really have a relatively narrow window of time to do something about the climate and greenhouse gases. And really, assisted evolution is not meant to replace any action on climate change. It’s in addition to action on climate change and conventional management. Really what we’re hoping to do is buy time for corals until we finally curb climate warming.

In one recent paper you wrote that assisted evolution, quote, ‘might contribute to the persistence of coral reefs until global warming is halted.’ Now, when do we need to halt this global warming? Is there a time frame around that? We should have done it like 25 years ago?

We should have done it way earlier. We always seem to wait until it’s almost too late before we do something, right? It’s very frustrating. Everything in the world is like that, it seems. And if you intervene early, it’s a lot easier, really. But that’s not what has happened. So, most models say that we will have annual mass bleaching at least by 2050. And there was a recent paper where the modelers looked at not just heating but also acidification and other disturbances. And they said, 2035 is maybe a cut-off date by which we should have really achieved something. So, that’s pretty scary. So, very soon.

Do you think the reef is done for you know, just in the plainest possible sense? We’ve been hearing about the threat to the Great Barrier Reef for 25 years, at least in Australia, since that 1998 mass bleaching event. Do you think people have given up? Do you think there’s a danger that people will give up?

There’s a danger, but there’s still hope. And I’m hopeful that technology will at least help us to buy that time. But then it’s really often due to governments to decide what are we going to do about regulating greenhouse gas emissions? And all the complexities because it’s a global issue and we know – but COP, the Paris Agreement and all of that. And will countries then actually stick to what they promised? That’s the challenge.

But I’m hopeful. I’m sure we will lose more reef. We will lose coral species for sure. And other species that live on the Great Barrier Reef. But I’m still at this moment hopeful that we can save something. And so, I think things will get worse. But I’m hoping that we will deal with the climate in the decades to come. And then in combination with technological developments, that once we get over this hurdle of a worse time, that hopefully we’ll eventually see some improvement.

So, what’s next for you, Madeleine? What’s the next step? You’ve shown that it works in the lab.

Yes. So, progression usually is first proof of concept in the lab, and then the next step is controlled small field trials, which is the stage that we are at now. And then once we can demonstrate that the intervention actually works in the field setting and also, we can – that allows us to assess the risk a little bit, like intended and unintended consequences. If that risk is deemed acceptable, then I think we’ll go to a large-scale deployment and really hopefully to implementing this as a restoration method.

Madeleine if anyone was going to play God, I couldn’t think of a better person than you. Good luck with your research and I would just like to ask everyone in the audience to join me in a round of applause.

Thank you.

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This is a significant new project for the museum and the records of these conversations will form a new climate change archive preserved for future generations in the Powerhouse collection of over 500,000 objects that tell the stories of our time. It is particularly important to First Nations peoples to preserve conversations like this, building on the oral histories and traditions of passing down our knowledges, sciences and innovations which we know allowed our Countries to thrive for tens of thousands of years.