The Microbial Partnerships That Help Corals Survive

Mark O. Martin (0:00)

From Microbe TV, this is Matters Microbial, a podcast about the wonders of microbiology, microbiologists, and microbial centrism. This episode was recorded live at the American Society for Microbiology meetings in Washington DC on June 7th, 2026

Thank you all for being here. By the way, up here, I have some buttons for those that are interested. No, you can't have Terence the tardigrade or Henrietta the helicobacter, but my guest today has for you as well.

Hannah Reich (0:35)

Stickers.

Mark O. Martin (0:38)

We strongly believe that this works. Hello, micronauts, and welcome to our quality quorum today, live from ASM Microbe in Washington DC. I'm your host, Dr. Mark Martin, Associate Professor of Biology at the University of Puget Sound in Tacoma, Washington. Today is the 133rd episode of Matters Microbial, and I'm grateful to every listen, view, and the emails that I get.

In many prior episodes of this podcast, we have discussed the primacy of microbial interactions, often in unexpected ways. Dr. Hannah Reich of the Department of Environmental Biology at the State University of New York's College of Environmental Science and Forestry is going to discuss some of her OMG, Overwhelming Microbial Greatness, as you recall, that they do on studying how the changing ocean conditions can alter trace metal exchanges in nutritional symbiosis, and evaluating how biogeochemistry, that's a word, mediates cellular communication within microalgal bacterial interaction, and in turn, the vast arrays of outcomes, including my favorite term, frenemies. Welcome to the Quality Quorum, Hannah. It's great to have you here live at ASM.

Hannah Reich (1:59)

Thank you for having me. It's great to be here at ASM. This is my first ASM.

Mark O. Martin (2:04)

It's your first?

Hannah Reich (2:05)

Yeah.

Mark O. Martin (2:06)

Okay. Well, the first thing that I want you to do is explain what a frenemy is.

Hannah Reich (2:11)

A frenemy, so that's a portmanteau of a friend and an enemy. So, the nature of the relationship can change.

Mark O. Martin (2:19)

So, this is an important concept for listeners and viewers to think about, where we really like to decide that the interaction between two members are always the same and it's simply not true. It's context, context, context.

So, you also have another word you want to introduce to us.

Hannah Reich (2:34)

Yeah, another made up word. So, this is the portmanteau that best describes my research, phycosymbiosis. I study algae and symbiotic relationships, and I got into this as someone who as an undergraduate used to say, I don't like to study things I can't see, and I've made a full 180

And now, I really enjoy studying microalgal interactions with my students. And this, what I call phycosymbiosis, the relationship between microalgae bacterial symbionts, and then sometimes animal hosts. And we're interested in this in both field studies and particularly in cell cultures, and how they scale up to ecological consequences, including coral bleaching outbreaks, and also thinking about algal blooms and some really rare year-round bioluminescent algal blooms. And then sometimes some friends and I in Central New York go fresh water sponge hunting. We're on the look for fresh water sponges with microalgal symbionts. Yeah.

Mark O. Martin (3:42)

I am loving the pictures that we're seeing here. Would you mind telling people about the horrors of coral bleaching, because this is relevant?

Hannah Reich (3:50)

Yeah. So may I skip a few slides ahead? I can do whatever I want.

Mark O. Martin (3:55)

This is your show.

Hannah Reich (3:56)

This is my show.

So when we're talking about coral bleaching outbreaks, or sometimes known as coral whitening, this is a result of the breakup of this nutritional symbiosis between the animal coral, the microalgal symbiont, and also communities of prokaryotes, bacteria, and archaea. Sometimes there are viruses involved, and the community of the coral host and its microbial symbionts, they work together and exchange different nutrient products, and that creates this large ecosystem of tropical reefs that you can sometimes see from space, and that usually brownish pigmentation color actually comes from microalgae, from the family Symbiodinaceae, and so the coral and the Symbiodinaceae, that's very eukaryote centrist of me, primarily that mutualism is what keeps up a healthy coral reef. However, when conditions are adverse, primarily referring to marine heat waves, so warming spells, that can result in the breakup of the Symbiosis, and in the breakup, in some instances, the algae is kicked out or the algae is expelled, there's a lot of ongoing research on how the onset of bleaching has actually occurred. But what happens on a large scale is that microbial expulsion of the symbiotic dinoflagellates that are really doing a lot of work for the coral symbiosis by way of providing sugars from photosynthesis, and that bleaching outbreak is the widespread symbiosis breakdown that can cause a large ecosystem shift where you're seeing whitened corals, and then also if temperatures or other adverse conditions don't recover quickly enough, they can be overgrown with turf macroalgae or not the macroalgae we want to see right now.