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Interview with Dr. Erinn Muller

Journalist: Luming Cao

Luming: Welcome to SciSection! My name is Luming, and I am your journalist for this episode. We're joined here today with Dr. Erinn Muller, the Program Manager and Science Director at Mote Marine Laboratory’s Elizabeth Moore International Center for Coral Research and Restoration. Thanks for taking the time to meet with me today.

Dr. Muller: Thanks for having me, Luming.

Luming: Let's just start from the very basics. So what kind of organism is a coral and what are coral reefs?

Dr. Muller: Yeah, that's a great question. And corals appear to be relatively simple. Sometimes when you look at them from the outside, they're like these colorful rocks that you see out in the water, but they're one of the most complex organisms in the world, I think. Corals are actually an animal; they're made up of individual polyps that kind of look like little anemones if you kind of get down really close and look at them, and those polyps can live individually, or most often they live in a colony. And that's why we kind of refer to corals as colonies, these little polyps that are connected to each other. And that's the animal portion of the coral. They are these little polyps with tentacles that kind of stick out and they grow through creating more and more polyps through time. They also have a really strong physical structure because they secrete a skeleton made of calcium carbonate. So it's like bones like us, you know, but they are secreting that from that polyp underneath that layer and building up kind of these boulders or branching corals through time, which give those corals different structures. And then to complicate things even more, corals, as the animal themselves, for the most part don't live alone. They have a unique mutualistic relationship with microbes. One of them in particular is a symbiotic algae generally called, and this algae live inside of the coral. It's a little single-cell algae that photosynthesizes from the sun, but the products of that photosynthesis actually are a lot of the food that the corals consumed. So the Zooxanthellae provide food for the coral and the coral provides a nice home for the Zooxanthellae. And then in addition to those two organisms, you also have a suite of bacteria: Some are commensal, some are probiotics, and some potentially could be pathogenic that also live in concert with this animal of the coral. So it's an extremely complex relationship, and that has to really all work out well in order for those corals to grow, be healthy, and eventually hopefully reproduce, which is what we want them to do for population persistence. And then your question about coral reefs, what are they in general? Coral reefs are the hard structure that accumulate often through thousands of years of accretion. And that accretion can be from often the skeletons of coral. So as corals grow, they're secreting that calcium carbonate skeleton when they die, that skeleton becomes a part of that physical reef structure. And so the more corals you have living and growing, that coral reef actually can grow through time. As it further creates, you know, as things change in the world like sea-level rise and things, you have these corals that can grow and make more reefs. And those reefs in general can provide a ton of different what we call ecosystem services, different benefits that humans use every single day, whether you know it or not.

Luming: Interesting. So can you talk more about why coral reefs are so important to the ecosystem and to humans?

Dr. Muller: Yeah, that's a really great question. And one of the things I love about working with coral reefs is because they are so… they're such an incredibly important ecosystem. So biologically the most diverse ecosystems in our ocean. About 25% of marine life relies on coral reefs at one point or another in their life stage. But in addition to that incredible biodiversity, reefs in general provide a lot of services to humans directly. So that physical structure that we just talked about with the reef offshore of land actually absorbs wave energy, and in doing so reduces erosion and protects our shorelines, so that can help save us on property destruction or any type of issues that could be related to wave force or wave height from storms. So they really help protect our land and our property. Coral reefs are actually a really important source of novel medicines. So there's organisms that live in coral reefs, and those organisms are incredibly unique and they create these unique compounds that you can't find anywhere else in the world. And we can harvest some of those compounds and use them to fight things like cancer or drug-resistant bacteria or memory loss. All of those are goals of, ways that we're harvesting medicine from the ocean. And then they're a huge economic driver. So for example, Florida's coral reef which expands from about central Southern Florida all the way down to Key West, and West to Key West to the Dry Tortugas is estimated to be worth at least 8 billion, with a B, billion dollars, to the state of Florida, or over 70,000 local jobs. And helps to attract, you know, 16 million visitors a year to our state. So it's like a boom to our economy. It's incredibly important for our heritage and for ecosystem health and biodiversity. So coral reefs are amazing, amazing ecosystems.

Luming: That’s really fascinating. So despite their importance, in recent years, we're hearing that coral reefs are dying like all over the world. So what are happening to the coral reefs?

Dr. Muller: Yeah, it is unfortunate. I, you know..

Dr. Muller: I say this almost on a daily basis, but you know, we're in the fight of our lives to try to save coral ecosystems. because we are losing them at an unprecedented rate worldwide.

Dr. Muller: So some of the major issues that are affecting reefs around the world, primarily increasing water temperatures from global climate change. And temperature is really important because corals live really close to their thermal tolerance, meaning only a couple degrees warmer in the water, and that symbiotic relationship that we talked about in the beginning about between the Zooxanthellae and the coral animal actually breaks down when the water temperature is high. They, the coral, spit out those Zooxanthellae, and they turn white because the Zooxanthellae actually are what are providing the beautiful colors that we see for corals in many ways. And that's why we call it bleaching because the corals are turning white. So with that loss, those Zooxanthellae, the corals eventually start to die. So that unfortunately is happening more often and more severe in places all around the world. And then, you know, locally at different reefs, you have other issues like in the Florida reef tract, we have huge disease outbreaks that are occurring, that are decimating a lot of our populations that are endemic to our region which could be related to things like climate change, could also be related to things like water quality and habitat degradation issues. And then there's also ocean acidification, which is the declining pH of our ocean. Carbon dioxide increases in the atmosphere. It actually gets absorbed into the ocean and through a series of chemical reactions reduces the pH, makes it water more acidic. And when that happens, corals have a really hard time acquiring the ions that they need to grow their skeleton. And they actually can… some of them could even potentially dissolve their skeleton through time. And so that is a main issue that we see becoming even more important as time goes on as carbon dioxide increases in the atmosphere. It's a lot of issues to deal with.

Luming: Hmm. I see. So you're a part of the Coral Health and Disease research team. Can you talk about your research?

Dr. Muller: Yeah, yeah. So my program, the Coral Health and Disease program at Mote really focuses on what makes coral sick. So what are the major global and local threats that are affecting corals primarily focused on the Florida reef tract, but also what makes corals healthy and the unique responses that we see sometimes when we expose different genotypes of corals to stress. So like you and I, we are not related. So we are different genotypes because we have different DNA. Corals, you can actually grow through fragmentation, very similar to like cutting of a plant. If you're a gardener, that's a way to really easily propagate lots of plants. You can propagate lots of corals similarly too, but you kind of in the population as a whole, you have a mixture of those identical twins out there, and then you have a mixture of different genotypes. What we see is that the genotypes sometimes respond very differently to these threats. And so what my research has really focused on now is figuring out which corals are resilient to some of those major threats. I'm trying to identify the mechanism behind that, whether it's ethnic or microbial or something that, you know, we haven't even explored yet. And I feed that information into Mote’s Coral Restoration Program. So, you know, we have a large number of people that focus on coral propagation and out planning for reforestation purposes. You know, we don't want to put corals back out onto the reef that are just going to die at the next bleaching event. So we want to increase genetic biodiversity in our outplant population, but also make sure that the corals that we're putting out there have a good chance of surviving, you know, for decades to come. And so a lot of my research helps to guide what corals they're putting out, what genotypes should be present, what's the genetic distribution of them. And then we can field test some of these experiments to make sure that what we see in the lab is really happening also underwater.

Luming: That's really cool. So you're testing… basically experimenting with different genotypes to see which ones are more resistant to the disease?

Dr. Muller: Yeah. So we'll look at things like disease-resistant genetic strains. And I have a really nice project with collaborators from Oregon State University who are studying the microbiome. So the bacterial community of those disease-resistant versus the disease-susceptible genotypes, because there seems to be a really unique signature that's probably driving that. We also look at thermal tolerance, so which ones are able to withstand, not just withstand increasing climate change or increasing water temperatures due to climate change, but still be able to continue to grow and reproduce, so that, you know, the corals that we put out there you know, next time don't just bleach and die need. We need to make sure that as those water temperatures unfortunately continue to climb, you know, we have a population that can at least withstand that until we get climate change under control.

Luming: Okay. I see. So you mentioned about a disease outbreak in Florida. Can you talk more about that? What happened?

Dr. Muller: Yeah, sure. You know, disease is a natural part of any ecosystem, but there's two large outbreaks that have really shaped the community of corals on the Florida reef tract. One happened decades ago in the late ’70s and early ’80s, it was called the white-band disease and it affected like 90% of our populations of the Staghorn and Elkhorn coral. So these are the two main branching corals that are found throughout the Caribbean and throughout Florida. And so that outbreak, which lasted multiple years and had large geographic reach really caused, or started, a very significant precipitous decline in the coral cover within the Florida Reef tract. And then in 2014, another outbreak began that we're still entrenched in, unfortunately, it is called the Stony coral tissue loss disease. This particular disease doesn't seem to affect those Staghorn and Elkhorn corals that were affected in the ’80s, which is quite interesting, but it does affect over a 20 to 25 and more of the other species that are kind of the last vestiges of corals out on the reef tract. So like the brain corals, the boulder corals, those are the ones that are getting most affected by the Stony coral tissue loss disease. So it has continued to spread. It began somewhere off the coast of Miami around 2014, it has appeared to be using water currents to spread. It's now pretty much throughout the entire Florida reef tract except the dry Tortugas, but it has jumped to other regions throughout the Caribbean and it's causing significant decline as it's kind of moving through the region. So since that outbreak, I mean, we've been,p you know, kind of putting all of our forces into understanding these. We're a significant contributor to this incredible organization called the Florida Department of Environmental Protection Disease Advisory Committee, which is like a consortium of experts in the region that are studying the disease, you know, in all different ways. There's members of that team that are looking at what's the pathogen; there's members of the team, looking at the ecology in the water; there's hydrodynamic modelers; there's people that are applying antibiotics to try to stop the disease from progressing and having some good success with that. So it's, unfortunately, you know, an extremely devastating disease, but it also has created this unprecedented opportunity to be a part of this huge regional and global effort to try to figure out how to combat that.

Luming: Yeah, so cool you are doing that! So can you talk about the academic path that led you to your work today and how did you get interested in marine biology in the first place?

Dr. Muller: Yeah, it's kind of funny that I ended up at Mote Marine Laboratory and Aquarium because my love for the ocean really started at a visit to our local aquarium in upstate New York where I grew up and in the region and we have family vacations where we would just cross the border into Canada and we'd go to the community aquariums there. And that's where I started my love for the ocean. And so it's kind of nice to be able to come back full circle and be at a public aquarium that, you know, hopefully shape minds like mine took to go into this field. But ever since I was a little girl, I just, I knew I wanted to study the ocean. If I was going to have a career that I spend most of my time developing, why not do it while in the ocean and study the amazing organisms that are there. So, you know, I was a very driven individual. I went to a high school camp in Long Island that really focused on marine science that I loved. And, and I ended up going to undergraduate at Florida Institute of Technology, which is a really well-respected marine biology undergraduate program. During my time there, I grew really interested in coral reef science and there was a professor there that studied, did his PhD in the Great Barrier Reef and kind of hopped from Australia over to Florida to develop his career. And so he really became a significant mentor of mine. And I ended up staying on with him for my graduate work, both my master's and my PhD. But during that same time, he encouraged me to go, you know, get experience in the field. And so while I did my graduate work, I also worked for the US Geological Survey in the US Virgin Islands and the National Park Service in the US Virgin Islands as a biologist studying coral diseases because it was the most significant threat affecting their coral populations at the time. So that really opened my eyes to the issue. It shaped the future of my research and I'm super grateful that, you know, I had so many opportunities to get my feet wet and get immersed in the science that I was able to eventually bring to Mote Marine Lab.

Luming: That's really amazing. So what are some of the challenges you have encountered in your research?

Dr. Muller: There's a lot. I mean, one of the biggest challenges that we have faced for decades and we continue to face today is that with coral diseases, it's really difficult to identify a particular pathogen. So it's hard for us to culture Marine bacteria in a Petri dish, which is part of the process for identifying pathogenic organisms. You have to be able to grow it, kind of in this controlled environment, and that's just not possible for most marine bacteria, which we believe are the causes of many coral diseases are, seem to be marine bacteria. They seem very responsive to things like antibiotics. You can't just dump antibiotics into the ocean of course, but you can treat corals in the laboratory setting with antibiotics or other types of therapies to try to figure out the pathogen, but the elusiveness of identifying coral disease pathogens has, you know, plagued us for decades. And it's the same thing with the Stony coral tissue loss disease. We know bacteria play an important role, but you know, we haven't been able to really isolate a single pathogen that could be identified as the bacterial agent responsible. And some people even think it's maybe a non- or abiotic factor that's actually being transported. And so there's a ton of work to do to try to figure it out. And we, you know, we maybe never will. I mean, that's pretty common in wildlife diseases, unfortunately. So that has been a big challenge in my research.

Luming: And on that note, thank you so much for talking with me today, Dr. Muller.


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