Our understanding of coral’s benefits grows every day—and so do the threats to this vital ecosystem. How are we affecting some of the critical relationships that let coral do so much for us?

In this episode of “Out of Curiosity,” Chico State professor Cawa Tran explains how her research on sea anemones, coral, algae, and the symbiotic relationships that tie us all together can help us learn not only how to preserve the reefs, but how to examine our own relationships.

Cawa Tran gestures as she speaks on stage in front of a sign reading "ED X Chico"
Chico State biological sciences professor Cawa Tran, seen speaking at 2018’s EDXChico event, has a unique way to examine the symbiotic relationships between coral and algae.


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KATE POST, HOST: This is Out of Curiosity, a podcast driven by the wonder of lifelong learning from California State University, Chico.

TRAVIS SOUDERS, HOST: Welcome to Out of Curiosity. I’m Travis Souders.

KATE: And I’m Kate Post. 

TRAVIS: What if I told you that thousands, if not millions, of living creatures depend on you, every moment of every day?

KATE: I’d say, “That’s a lot of pressure.”

TRAVIS: It’s true! Human beings play host to organisms of all kinds—various microbes, eyelash mites, gut bacteria—and they all have different levels of usefulness to us as we provide them with a place to live. Though we can’t see these symbiotic interactions taking place, they’re integral to our health, and the survival of our microscopic friends.

KATE: Today on Out of Curiosity, we examine the delicate balance of symbiotic relationships in the world’s coral reefs—how they thrive, how they help us, how we can protect them from the dangers they’re facing, and how we can learn from them.

TRAVIS: Today’s guest is professor Cawa Tran, a biological scientist specializing in cellular and molecular biology. 

CAWA TRAN: Let’s talk about why we care about coral reefs first, let’s start there. Coral reefs worldwide are ecologically, economically, and aesthetically important in the sense that it is home to many, many types of fish, and marine invertebrates, and algae, and so it’s this whole ecosystem that houses so many animals and plants. And so, therefore, they’re important in the sense of biodiversity, for one, and because of how beautiful they are—any time, if you’ve ever gone snorkeling or diving over a coral reef, you see these beautiful colors that corals produce, and so they have aesthetic value in that sense, which makes them important for tourism, for example. And so, a lot of island nations, for example, depend on that tourism to help their economy, so in terms of visitors being interested in diving and snorkeling and fishing, that’s how they contribute economically. Along those lines, in helping island communities, because they have this hard calcareous skeleton, they make these large formations that essentially act as a natural barrier for waves, tsunamis, storm surges … so coastal protection is something else that they offer as well. Along those lines, I’ve already mentioned, home to many fish, so they are important to fisheries and our food. Finally, something that really catches the attention of my pre-med students I teach a lot of the time, I say the magic word “medicine,” and that is a lot of antimalarial and anticancer compounds being derived from certain species of corals and sponges within a coral reef. So there’s a lot of active new drug discovery research that comes from our oceans. If you think about, within an ocean, what’s one of the largest ecosystems there are out there, it’s a coral reef.

TRAVIS: Professor Tran grew up in Hawaii and with an innate sense of the value of coral reefs from the beginning, but she has continued her research here in Chico. Raising awareness about the importance of this ecosystem might be a globally important mission, but it’s mostly a blind spot for mainlanders in particular.

CAWA: I did my PhD at the University of Hawaii on the island of Oahu, the coral reefs are your backyard, so you understand, living on an island, you understand the importance of a coral reef, and I’m not sure if some of the voices from folks from other island communities are being heard in that sense. When you’re living in the middle of the Pacific Ocean, you get it. The folks in Hawaii, researchers, even the lay person in Hawaii, they get it. If they were to talk to someone from the Marshall Islands, or from Guam, they get it, in terms of the importance of this coral reef.

KATE: To perform research of these cnidarians 200 miles from the nearest ocean, Professor Tran studies another animal in her Chico State lab that shares some similarities with coral. Specifically, she uses a proxy—a sea anemone known as Aiptasia, which, like coral, is a host for algae.

CAWA: Symbiosis is about organisms living in close association with each other. In my case, I’m looking at a sea anemone, which is a cnidarian, and they are related to corals, related to jellyfish, and they have a symbiotic relationship with these algae that actually live within them. Many people know the term “symbiosis” as partners in close association with each other, but these guys I work with, they have the algae living within their cells, so it’s an algal cell within an animal cell and hence called an endosymbiosis. They mutually benefit from each other, hence they do work together. They do work together to survive, in which the cnidarians are providing shelter to these algae and the algae photosynthesise and in turn provide photosynthetic products as energy back to their animal host. As human beings, we are in close associations with microorganisms as well. We’ve heard of gut bacteria and how important they are, so we are in symbiotic relationships everywhere.

TRAVIS: How does this all apply to us? Well, human beings are a third party when it comes to the symbiosis between coral reefs and the algae inside of them. As Professor Tran explained, our species benefits from coral health—but what happens when we don’t contribute to the relationship? When temperatures rise, or pollutants affect the coral reefs, they suffer, the algae suffers, and ultimately, we suffer.

CAWA: In response to, let’s say, heat stress for example—one of the factors associated with climate change—in response to heat stress, this symbiotic relationship can break down and the animal host can actually expel the algae. When the algae leave, that hurts the coral in a sense, where over time, if the corals can’t regain their algal symbionts, their animal tissue can slough off and they can die. What gets left behind is that white calcareous skeleton, hence coral bleaching. And so, within the last decade or so, many researchers have spent a lot of time studying the symbiotic relationship between corals and algae. Marine debris from pollution can affect coral reefs. Agricultural runoff that would introduce herbicides can also end up seeping into the ocean. And I don’t know if you’ve recently heard of some detriments of the use of sunscreen that can contain oxybenzone, so folks are recommending that using mineral sunscreens like zinc oxide and titanium oxide would not only protect you from UV protection but also help the reefs. So it’s not just global climate change, I’ll put it that way. There are factors that we as humans are also introducing into our oceans that can really disturb the symbiotic relationship.

KATE: Human factors are stressing the ocean environments to the point that our coral reefs—which are so vital to humanity—are in real danger. And that puts humans in danger, too. If we consider ourselves part of this symbiosis, we’re the toxic ones in the relationship.

TRAVIS: But we could play a role in reversing that.

CAWA: It’s something as simple as… reducing your carbon footprint might contribute to that, because certainly beyond the warming of the oceans, what’s also associated with global climate change is this increase in CO2 that would change the chemistry of the oceans and make the oceans more acidic, and as it lowers its pH, that can also affect corals in a different way, and that is that their calcareous skeleton can break down and they can have a more difficult time building these natural barriers I’m talking about. If we are to zoom out and look at all of this, there are direct ways that we are affecting our oceans, and there are indirect ways as well.

KATE: We certainly have work to do in helping the coral reefs and preserving all the benefits they offer us. But we also can still learn from the nature of their symbiotic relationships. In our work lives, our studies, our social interactions, we all face uncertainties. The lesson Professor Tran likes to teach is that we can take a lesson from our invertebrate friends: We are at our strongest when we lean into our closest relationships.

CAWA: We as human beings can stress out as well, right, in terms of, especially if I’m thinking about, you know, being a student at a new place, just starting off college, there can be a lot of stressors in place, in terms of getting to know what the college experience is like, or going through your four years and dealing with other stressors that come into play as well, whether it’s about maybe not doing so well in a class, or something happening in your personal life. I know all of those factors have intersected with my college experience as well, and so these are stressors. And so, at that point, you have to think about, well, what do you do in response to stress? And I would say, one place to look at is the relationships in your life, and the symbiotic relationships that you might have with your family, with your friends, folks who can actually be supportive for you. So, in a sense, I feel that that is similar to the corals and the stressors that they go to, and if there is a stressor, how do you deal with it is the thing. You go back to relying on the symbiotic relationships you have already in place.


CAWA: I like this concept of working together, and thinking about ways in which we can use that as a theme, basically, in our lives, and cooperating rather than competing.

KATE: Thank you to our guest, Cawa Tran. This has been “Out of Curiosity.” I’m Kate Post.

TRAVIS: And I’m Travis Souders. This show is produced by the office of University Communications at California State University, Chico. Make sure you never miss an episode by subscribing wherever you listen to podcasts.