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Superorganism Spotlight: Raquel Peixoto, PhD, on How Probiotics Could Help Save Coral Reefs

5 minutes

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Here, we’re speaking with coral microbiologist and Seed Scientific Board Member Peixoto, PhD, on her work developing probiotics to support the health of coral reefs.

Corals are integral to the health of the entire ocean ecosystem and beyond. But a host of threats have put coral reefs at risk of worldwide collapse within the next decade. Dr. Raquel Peixoto’s work focuses on supporting coral reefs with beneficial probiotics. She specifically pinpointed key microbial players involved in making corals more tolerant to oceanic temperature change.

Continue exploring conversations about the fascinating world of bacteria and the vital role they could play in saving our planet here.

If you were meeting someone at a party, how would you describe the work you do? 

“I’m developing probiotic medicine to help corals cope with climate change and all of the resulting threats they’re exposed to. Corals—like you—have a microbiome, and certain probiotic species have been shown to help corals fight pathogens, recycle nutrients, clear waste, protect against UV rays, and ameliorate the damage caused by human-induced climate change. So what I do with my team is grow the beneficial bacteria (i.e., probiotics) in the lab, and then we apply them back to corals.”

What does a world without coral reefs look like?

“Corals are the canaries in the coal mine when it comes to the ocean. They are the foundation species of the most sensitive ecosystem—coral reefs—and they are connected to other marine ecosystems that are also affected by human activities. At least one-third of all marine life rely on coral reefs, so if they’re gone, all of these other organisms will also be impacted, which will ultimately impact the other ecosystems that are connected with them. 

“The corals also dissipate some of the energy that comes with the waves, so it’s more likely that coastal countries will be affected by waves and storms. Tourism will also be heavily impacted, especially in countries that rely heavily on the tourism of coral reefs. And even if you live very far from a reef, you’ll be affected because the food web will be impacted—if you think back to that one-third of marine life being impacted. It would be an event with global proportions like Covid, but the difference is that there will be no vaccine. Once corals are gone, they’re gone. So we need to prevent this from happening in the first place.”

Whether we’re talking about the planet or our own microbiomes, we all need to try to be more symbiotic and less pathogenic. And I believe we can.

Dr. Raquel Peixoto

How is climate change affecting corals?

“Seawater temperature increase triggers a cascade of problems inside corals. One example is the symbiotic interaction between the corals and the photosynthetic algae that live within them. With the temperature rise, they start to compete with each other, rather than be symbiotic, and their relationship breaks down. For most shallow reef corals, up to 80% of their energy comes from the photosynthetic algae. When the algae becomes a competitor, the coral has to get rid of them, so they kick them out. This is what’s called ‘coral bleaching,’ because the algae has most of the pigment. 

“The coral also has to cope with the absence of this energy. That means that the coral will continue to be alive for a while, because they can rely on the microbiome and heterotrophic feeding for short periods of time. Once the temperature is back to normal, the algae should return. The thing is that, the time that it takes for the algae to return will actually define whether this coral will die or not. So if it’s a long period of time and the corals are very stressed, they will die before the algae can return. When we think about medicines, it’s a matter of buying time. We need to buy time. We need the coral to stay alive until the temperature is back to normal so that the algae may return. That’s more or less what we’re trying to do with probiotics.

“What you have to keep in mind is that coral bleaching caused by thermal stress is the main problem, but it’s not the only problem. There are lots of other pressures, like overfishing and pollution. All of these local impacts will maximize the problems caused by global warming. So the solution to actually save coral reefs is to minimize CO2 emissions and to minimize and mitigate local pollution. But even if we do all that, we still need to work on active restoration of the coral reefs because of the current degradation of the reefs. We have already damaged it beyond what the reef is capable of handling, and we have emitted CO2 that will continue to cause annual bleaching events, even if we stop the emissions right now.”

Why, exactly, do corals need probiotics?

“When corals are impacted by climate change, there are two things that they have to cope with: 1.) The absence of beneficial bacteria, and 2.) the presence of pathogens that are now more competitive in the reef. By helping corals retain the beneficial bacteria, we occupy the niche and promote competition, which means that the pathogens will have difficulty colonizing corals. We also keep providing them with the benefits that the holobiont needs. 

“This is the same for corals, for humans, for fish, for frogs, etc.—all of them, when exposed to stress, may experience negative impacts on the microbiome. Microbes can also be sensitive to stress. We rely on our microbiome, all of us. The microbial ecology of our guts and our bodies is very important because if we manage to retain the beneficial bacteria, they will fight pathogens, which supports our health. It’s a matter of ecology. Even if the bacterial groups are not the same across these different hosts, the principle is the same.”

Dr. Peixoto applying probiotics to corals.

How do you get the probiotics to the corals?

“We’ve been developing several different approaches to that. We started delivering probiotics manually and applying them with syringes to prove the concept and also have a well-controlled way to deliver it. But in parallel, we’re developing bacterial pills. These encapsulations that we deliver to the reef release bacteria slowly and continuously. They work similarly to nicotine patches. We’ve also developed an automated dispenser called Coral AI™ that works like an irrigation system you’d have in your backyard. We program the irrigation system, and it delivers the bacteria to the reef. We can keep that system there for weeks without having to go back to the reef. 

“Right now, we’re testing these in the reef for the first time, so we are translating a lot of the knowledge we gained in the lab into the real world. We’re trying the first pilot tests of these systems in the reef in a very well-controlled way, and the delivery systems are working. So now we have to see if they are actually beneficial for the reef. 

“We’re testing these in what we’re calling the Coral Probiotics Village, an underwater city that we established in the Red Sea. We have gates and streets and a map with all of the corals we’ve been inoculating. We started tagging corals and connecting them with roads to save time so that we could easily find the next colony that needs to be inoculated. We’ve been using the street names to locate ourselves in the water. It’s a very well-monitored place—we go to the Coral Probiotics Village at least three times a week every week and have been monitoring the environment and non-target organisms as well.” 

How can people support the work you do? 

“One thing everyone can do is raise awareness and pressure stakeholders to take action. We can do this every time we choose our representatives and every time we use social media. Be an advocate for corals and an advocate for biodiversity overall. Of course, we can improve our individual lifestyles and contribute by balancing our carbon footprints, but I think there needs to be a way bigger effort. We need to use our power to guide companies and governments to do what’s right, and that needs to be done now. That sense of urgency is something that we need to advocate for. We know what has to be done, and we know how to do it; we now need stakeholders to take action.”

What’s giving you hope?

“Every single action matters a lot. You have to continue to feel motivated because, while you are one person, you can influence other people, and you can spread the benefits of doing what you’re doing. You set an important example for younger generations, and you put economic pressure on stakeholders to be more sustainable. 


“At the end of the day, it’s a matter of ecology. It’s a matter of maintaining balance at all the different levels, from the microbiome that lives within us to the way we interact with the ecosystems. It’s all a matter of symbiosis. Whether we’re talking about the planet or our own microbiomes, we all need to try to be more symbiotic and less pathogenic. And I believe we can—we can be more symbiotic.”