A New Hope For Corals

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Over the past few years, news about coral reefs around the world has not been good. Coral populations have been declining dramatically, with climate change remaining a big threat. But this month, we got some good news about corals in the Florida Keys. Here to tell us about it is Dr. Hanna Koch, a postdoctoral research fellow at the Mote Marine Laboratory and Aquarium in Summerland Key, Florida. Welcome, Hanna.

HANNA KOCH: Hi, thank you for having me.

IRA FLATOW: All right, give us the good news. What’s the good news?

HANNA KOCH: Oh, well, the great news is that we have documented for the first time worldwide restored corals of a slow-growing mountainous star coral species to be sexually reproductively viable and spawn for the first time in nature.

IRA FLATOW: Where was this done? Tell me exactly what you did.

HANNA KOCH: So Mote has pioneered this technology called micro fragmentation fusion, which is where we will take a colony, we will cut it up into small replicate pieces, grow it in our land nursery, and then we will out-plant those pieces onto a degraded coral head. And those replicate pieces will grow and fuse. So that’s the fusion part of that methodology.

And essentially, they will form a larger colony faster. And the reason why that is so important is because for many stony coral species, sexual maturity is a condition of size, not age. So you can think of it like puberty. And so it just means that they have to reach a minimum size in order to produce the next generation of baby corals.

And so with this breakthrough, we’ve basically been able to show that with this methodology we can create reproductively viable corals of a slow-growing mass of species within only a handful of years instead of decades. Because in nature, wild corals would take about 10, to 20, 30, and so on, decades, to reach sexual maturity and produce the next generation.

So the fact that we can cut that down significantly to just a handful of years is really a breakthrough for coral restoration science in general, and bodes well for the faster recovery of our reefs and of our restored populations.

IRA FLATOW: Have you tried to repopulate a dead coral reef with these new babies?

HANNA KOCH: Yes, so Mote engages in multi-species coral reef restoration, also resilience-based restoration. And so we out-plant thousands of fragments of different species, species that are all key reef building species. And what that means is that these species are foundational species. They’re the ones that create the backbone of our reefs. And we have been carrying out coral reef restoration for several years now for a number of different species. And this year was really exciting because it was the first year that we had multiple populations of different species that we restored to the reefs actually become sexually mature and spawn.

IRA FLATOW: And what were the major hurdles that you had to jump over?

HANNA KOCH: Well, one thing is that corals grow slowly in general. And then we have to deal with the stressors that are happening naturally in the environment. So, for example, these corals that spawned, we out-planted them in 2015. And in 2015, there was a global bleaching event. In 2017, the Florida Keys experienced a category 4 hurricane, Irma. And in 2019, that site was hit by the stony coral tissue loss disease, which is the deadliest coral disease outbreak ever recorded on a contemporary reef, and certainly for Florida’s coral reef.

So we are doing our best to restore these corals and these species, and use a variety of science-based strategies, but we always have to deal with natural, unpredictable events that happen in nature. But the fact that our corals are surviving these natural stressful events, and able to have enough energy to put toward sexual reproduction is great. It gives us optimism, and hope, and shows that what we’re doing is working, and that it should continue to work as we move forward.

IRA FLATOW: These are really resilient corals it looks like. Did you have to go find this species or this kind of coral that you would expect to be able to overcome these hurdles?

HANNA KOCH: We’ll find them in nature. So because Florida’s coral reef has already experienced a number of stressors over the last decades, many of the corals that are out there today are already considered resilient. They’ve already gone through stressful events. And so they’re survivors for a reason. And so we can use those survivors to propagate more corals.

Another method is that we will expose these corals to different stressors or different combinations of stressors, like high temperature or different diseases, find the strains that are resilient or resistant to these stressors, and then propagate them. And when we out-plant and restore corals, two ways that we can ensure resilience is, one, making sure that we put out high genetic diversity.

So we’re not putting out just a few of what are considered the best or the top performers, because the environment can always change. So we put out high genetic diversity, but we also put out corals and strains that we have tested in the lab, using controlled experiments to identify those strains that are resilient to the different stressors. So we can make sure that we’re putting out corals that have a higher chance of surviving.

IRA FLATOW: I’m sure you’ll be keeping an eye on these out-planted corals for a while. That’s a term– out-planted– that I hadn’t heard before. What will you be looking for?

HANNA KOCH: So moving forward, part of my job as a coral reproduction scientist is to continue to monitor the health, the survival, the growth of our corals as part of our restored populations. Also to monitor the sexual maturity of these populations, looking at what proportion become sexually mature over time. Are they continuing to reproduce sexually and produce the next generation of offspring every year?

Also, we conduct multi-species restoration. So I will apply these monitoring assessments to all the species that we out-plant. And also, monitor for other critical developmental milestones. So spawning is only one aspect of the sexual cycle. You still have to have fertilization and settlement, meaning the larvae will settle back down onto the reef, undergo metamorphosis, and develop into a coral that becomes a part of the adult population. And so every one of these aspects is critical to becoming a self-sustaining population. And so moving forward, I will monitor for those other critical developmental milestones.

IRA FLATOW: I want to bring on another coral expert so that we can talk a little more about the state of corals in 2020. Dr Holly Putnam is an assistant professor of biology at the University of Rhode Island in Kingston. Welcome to Science Friday.

HOLLY PUTNAM: Hi, thanks for having me.

IRA FLATOW: Good news that we’re hearing out of Florida to you?

HOLLY PUTNAM: Yes, I think it’s fantastic news. I think in these times, any positive news is good, and any positive news for corals is definitely great.

IRA FLATOW: And do you think that you and other coral scientists can apply this specific method for coral populations around the world?

HOLLY PUTNAM: Definitely. I think that these kinds of restoration approaches are growing in capacity, growing in scale, and growing in the science-based nature of them. And that’s where really our work is focused, in the science-based nature of these, to not only grow corals out in the wild, but track many of these features that Hanna is talking about, to track their physiology, track their performance, track the generations as they move through. So being able to fragment corals, have them grow quickly, be out-planted, or be housed in nurseries and then out-planted provides this aspect for a variety of species and a variety of locations.

IRA FLATOW: We’ve been hearing so much bad news about corals over the past few years, how are they doing in 2020?

HOLLY PUTNAM: That’s a great question. I think, sadly, a lot of this bad news is correct and it’s continuing. I think as we watch climate change continue to occur, as seawater temperatures increase, as we get more heatwaves occurring, as we get more tropical storms, we are seeing negative effects on corals. We’re seeing those negative effects that are removing these large adult colonies from the populations.

That makes it harder for corals to make a comeback after these perturbation or disturbance events. And so overall, though, we still have thriving reefs around the globe. We definitely have hard-hit areas, and we definitely have global trajectories that are in a negative decline.

IRA FLATOW: Hanna, what about in Florida where you are? As a scuba diver, I’ve gone back to places that I used to scuba dive in, and there’s so many dead and dying corals in those areas. Give us an idea of what the population is doing in Florida, in your region.

HANNA KOCH: So, as Holly already mentioned, there are certain regions that have been especially hard hit. And Florida’s coral reef is definitely one of those regions. Some of the key reef building species in this area have experienced greater than 90% population declines and are now facing functional extinction. Which basically means that the populations are so small that they can no longer provide critical reef habitat structure or shelter for other important marine organisms, like fish.

It also means that their populations are so small that they cannot effectively undergo sexual reproduction and produce the next generation of corals that can replenish depleted adult populations. So we have a number of species that are facing this level. And we do have a species that are considered locally extinct. And I have to say that, despite the sad state of corals here, I have to say that I think 2020 has provided a lot of hope, a lot of optimism.

We’ve seen a number of organizations come together, state, local, federal, to engage in the NOAA seven iconics reefs mission. They’re putting $97 million over a 15-year period to restore seven key cites along Florida’s coral reef. So Mote is a part of that initiative. As I said before, we documented for the first time that many of our restored populations are sexually mature and spawning.

And then I also want to add that for the mountainous dark coral species that we documented for the first time to spawn after the micro fragmentation fusion methodology, some of the plants that we did observe to spawn last week, were out-plants that I observed to contract the stony coral tissue loss disease last year. They were treated with antibiotics, and we’re able to recover from this deadly disease, and still be reproductively viable the following year.

And I have to say that that provides immense hope for us, that we can make a difference. And if we just continue to work together and engage in these science-based restoration strategies that we will make a difference. And hopefully, in a short amount of time than what we may have initially expected, that we will see greater accomplishments for population recovery for these critical species.

IRA FLATOW: I’m Ira Flatow and this is Science Friday from WNYC studios. In case you’re just joining us, we’re continuing our conversation about the state of corals in 2020 with Dr Hanna Koch, postdoctoral research fellow at the Mote Marine Laboratory and Aquarium in Summerland Key, Florida, Dr Holly Putnam, assistant professor of biology at the University of Rhode Island in Kingston. Dr Koch, what was your secret sauce for getting these corals to grow so quickly and being able to collapse something that might take a decade or more into just a few years?

HANNA KOCH: That’s a great question. And we are still investigating the mechanisms behind this increased growth response we see once we cut a coral. But when we take these colonies and we cut them into smaller pieces, it elicits this growth response that allows them to grow faster. So if you think about a cut on your arm or something like that, you tend to heal quite fast. So it will heal over a few days. And your cells will regrow and cover that wound.

And so we are looking into what it is that really drives that response in terms of faster growth when you do cut a coral, using appropriate techniques. And basically, we’ve shown that through this micro fragmentation fusion process, that when we do cut the coral, it elicits a growth response that allows them to grow 25 to 50 times faster than just a natural coral in the wild would grow.

And so for a species that grows anywhere from half a centimeter to a centimeter a year, we’re able to actually produce decades sized colonies within only two to three years.

IRA FLATOW: That’s amazing. That’s absolutely amazing. Dr Putnam, tell us what the big issues we need to keep an eye on that are going to impact coral health around the world.

HOLLY PUTNAM: Yes, I would say the biggest issues at this point are at the global scale. So the biggest issues we’re seeing that are causing mass mortality are things like increased sea water temperature and marine heatwaves. And these are driven by increases in atmospheric CO2 and greenhouse gas concentrations, obviously that are driving the warming of the atmosphere, which is translating to driving warming of the ocean.

And this change in the overall climate is creating these marine heat waves and creating greater high-frequency and larger storms. So we have overall disruption to the environment that the corals are growing in. And the reason why heat is such a big deal for corals is because it can break down this relationship or this symbiosis that the corals have with their single-celled algae living inside them. The coral expels, or that algae leaves the coral. And you can see through the coral tissues. And that that’s what we call coral bleaching.

And when the corals are bleached, they’re essentially starving. Because they don’t have that energy that’s being generated by the single cell, the algae inside the coral. And so that’s how we can get basically a lower overall health of the coral. They can be more sensitive to things like disease, and to pollution, and to local effects.

So the overarching driver of increases in temperature are driving coral bleaching and driving loss of corals on the reef, when this heating and this bleaching is prolonged. In addition to that, we have the concern of ocean acidification. The overall impacts on the reef are more variable. While scientific studies show sensitivity for corals growing under ocean acidification, which is the uptake of CO2 from the atmosphere into the oceans that’s driving a decline in the pH of the oceans, making it energetically harder for them to calcify and to get these building blocks of their skeletons.

We see these declines in experiments in the lab. But there’s a lot of variation there in different species out on the reef. So we’re keeping an eye on ocean acidification and it contributes to the decline of coral calcification. So I would say at this global scale, we’re talking about ocean warming and ocean acidification.

And then the local scale, we’re talking about local human impacts. So nutrient runoff onto the reefs that can disrupt the balance of coral growth versus algal growth that can disrupt that, such that are taking over all the space that’s usually taken up by corals and can be smothering them. We can have other pollutants running off on the coral reefs. And all of these things together are contributing to increases in diseases.

So basically, we’re seeing this higher sensitivity because of both global and local stressors coming together. And so if we can take care of these global stressors, we have a better chance at dealing with local stressors, the corals dealing with local stressors. And we can actually take action again at a local level and mitigate those local stressors. So really, global action is critical and local action is crucial.

IRA FLATOW: Well, at least we got some good news today out of Florida and the restoration of the reefs there that might be applied to the rest of the world. I would like to thank both of you for taking time with us today. Dr Hanna Koch, postdoctoral research fellow at the Mote Marine Laboratory and Aquarium in Summerland Key, Florida, Dr Holly Putnam, assistant professor of biology at the University of Rhode Island in Kingston. Thank you both for taking time to be with us today.

HANNA KOCH: Thank you so much.

HOLLY PUTNAM: Thank you so much. And thank you for highlighting corals.

IRA FLATOW: You’re Welcome. One of my favorite topics.

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