Biogeochemistry as Ecosystem Accounting: Dr. Emily Bernhardt

Headshot of Dr. Emily Bernhardt, woman with shoulder-length hair

In this episode of BioGist, Emily Nagamoto, a member of the class of 2024 majoring in Earth and Climate Sciences, interviews Dr. Emily Bernhardt, the James B. Duke professor of Biology and the chair of the Biology department at Duke University.

Listen to hear Dr. Bernhardt define what biogeochemistry is, detail how she and her lab measure the cycling of elements, and describe how chopping vegetables help her destress.

To find out more about Dr. Bernhardt, visit her lab website at, and follow her on Twitter @DrBioGC.


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wetlands, elements, lab, salt marsh, water, ecosystems, duke, biology, ecologist, chemistry


Emily Nagamoto, Dr. Emily Bernhardt

Emily Nagamoto  00:01

Welcome to BioGist, where we bring you the gist of biology at Duke University. I'm Emily Nakamoto, a freshman at Duke, and today I'm here with Dr. Emily Bernhardt, the James B. Duke distinguished professor of biology. Dr. Bernhardt, thank you so much for joining me.

Dr. Emily Bernhardt  00:15

So glad to be here.

Emily Nagamoto  00:17

It's so great to be interviewing another Emily. So this is exciting [laughs]. So let's get right into it. What do you study?

Dr. Emily Bernhardt  00:24

I am an ecosystem ecologist and a biogeochemist. I study the way elements move through the environment. And mostly what my work does is look at the way humans are changing landscapes, changing the water chemistry and biodiversity of rivers and wetlands.

Emily Nagamoto  00:41

And how did you get into that? Why have you started studying that?

Dr. Emily Bernhardt  00:45

I thought I wanted to be a wetlands ecologist when I was a senior in high school, which is a weird thing to want at that stage. But I wanted it because my family spent most of our vacations camping in National Parks, we spent a bunch of time at Assateague. Island National Wildlife Refuge, on the coast of Maryland. I spent a ton of time like catching crabs and clams and mussels, I just loved salt marshes. I read a book after my junior year, while there, called Life and Death of the Salt Marsh, and I was like "this is amazing, I want to study this". I didn't know the term biogeochemistry. But I had gotten excited about those ideas, even while High School.

Emily Nagamoto  01:17

And what does the term "biogeochemistry" mean?

Dr. Emily Bernhardt  01:21

The chemistry of our Earth cannot be understood in the absence of biology. So that chemistry of the Earth is biogeochemistry. Since the very first life began on Earth, life has been really changing the way our Earth's surface and our atmosphere and interaction between the living and nonliving parts of ecosystems and the exchange of energy and materials between them. It sounds very intimidating, but really, it's accounting. It's just like tracking elements and energy through natural systems.

Emily Nagamoto  01:48

And why is tracking those things important?

Dr. Emily Bernhardt  01:51

Well, I think it's the fundamental linkages between organisms, right? It's, you know, how does the machine of life turns solar energy into the incredible diversity of animals on this planet, right? There's a sort of thermodynamic constraint on that, how much energy is available to fuel life. And then there's also the recipe of life carbon, the nitrogen, the hydrogen, the oxygen, the phosphorus, the sulfur, all those elements essential for life in the right proportions. So it really is sort of fundamental to the way nature works. And the other reason why it's so important is that humans are doing really great work, changing the distribution of elements on Earth, changing the seat of energy to many ecosystems on Earth.

Emily Nagamoto  02:31

So how do you study the cycling of elements? And where do you go? What does your team do?

Dr. Emily Bernhardt  02:37

Yeah, so the work of being a biochemist is super glamorous, we spend a lot of time going out into the woods or into wetland and taking samples of water and soil or vegetation, and then bring them back to the lab to see what the element concentrations are. And then also lots of work to try and do the hard part, which is trying to measure the rates at which elements move between one compartment and another or between, you know, the organic living form versus the sort of dissolved trace form. So it's basically measuring a lot of mud and water is a lot of what we do.

Emily Nagamoto  03:07

So what would a typical day look like in the field with you guys, and in the lab?

Dr. Emily Bernhardt  03:14

Okay, in the field, you would expect to get extremely hot, dirty, tired and at the end of the day coming out with a cooler full of water and mud and or vegetation samples. And in the lab, you would be spending a lot of time pouring off water samples, grinding up soil samples, packaging them into tiny little containers and then running them through machines. In either case, you know, you've got a big question. But of course, the work to answer that question often involves a whole lot of very tedious, repetitive activities, so get to keep your eye on why you're doing it. One of the things I love about running a lab, our lab is usually anywhere between 10 to 20 people that includes undergraduate researchers, we sometimes have high school researchers, graduate students, and postdocs, and then a number of technicians. And what I love is that in our group, we can have 16 year olds to mid 40s people all working together in teams that really are all bringing their own insights, perspectives and questions together. It's really fun. And I love to see undergrads just go from the point of like doing the tedious work that is usually the sort of starting point in labs to beginning to ask their own questions and beginning to sort of see that they can actually answer them. So going from studying science to doing science is really one of my favorite parts of the job.

Emily Nagamoto  04:26

So when I think of like a lab, I think of maybe one research question that people are working on, but how many different projects or different questions are people trying to answer in your lab?

Dr. Emily Bernhardt  04:36

When people ask me, what do we do? I would say we always use the same approaches, which is we're going out and measuring elements, you know, organisms and water and soil and vegetation. But we ask questions in really different environments. So I have we've had a project last five years in Peru looking at artisanal gold mining and mercury mobilization and pollution throughout the Amazon. We have a big project here in Durham, looking at how the way we put pavement in the city changes the flow and the chemistry of rivers and what that means for biodiversity. We have a project in West Virginia looking at how coal mining affects biodiversity and water chemistry. And then we have a huge project that's been going on for a long time on the coastal plain looking at saltwater intrusion and sea level rise and how that's changing because the wetlands are leading to all these ghost forest as trees die from salinization and flooding. So we kind of use the same approach. But what I like about biogeochemistry is you can take that approach and you can apply it to all these different questions, because in every case, something has been changed about the way water or elements or energy moves to that system, and you can study it and that can help you understand how you might go about mitigating that problem.

Emily Nagamoto  05:40

Let's shift gears a little bit. What is one thing that you love doing outside of work?

Dr. Emily Bernhardt  05:44

I love cooking. I particularly love cooking when I've had a stressful day, particularly the chopping of vegetables, I find very good for stress [laughs]. But I really love to cook and to eat good food. And I just enjoy like trying all different kinds of cuisines and both trying the restaurant then trying to replicate them and have some of my favorite hobbies.

Emily Nagamoto  06:05

Well, that's about all the time we have for today. Thank you so much, Dr. Bernhardt for joining me.

Dr. Emily Bernhardt  06:10

So glad to have the chance to talk to you.

Emily Nagamoto  06:12

Thank you for listening. And thank you to the Duke biology department for supporting this podcast, as well as Poddington Bear for the music. See you next time.