COVID-19 forces a change in plans for researchers studying global photosynthesis

In early January, BIO5 Institute members Laura Meredith and Jana U’Ren were planning a summer trip to Alaska to collect field samples for their newly funded climate change study – but as COVID-19 rapidly spread across the globe, the team quickly realized they needed to pivot their original plans. 

Meredith, an assistant professor in School of Natural Resources and the Environment, and U’Ren, an assistant professor of biosystems engineering, were awarded nearly $700K from the National Science Foundation to gather information on the sources and sinks of carbonyl sulfide (OCS), an alternative atmospheric tracer for carbon dioxide (CO2) to estimate global photosynthesis. 

Combining their expertise in microbial and soil ecology, the pair aim to use OCS to better understand how much carbon plants and soils remove from the atmosphere, which is critical to understanding the impacts of climate change on Earth's carbon cycle.    

I spoke with the cross-disciplinary team to learn more about their project, how they’ve adapted their plans since the onset of the pandemic, and their aims to educate the public about their work at Biosphere 2. 

You and your team were planning to travel to Alaska to collect field samples this summer, but you unfortunately had to delay your plans because of the COVID-19 pandemic? How have you altered your project to adapt to this unexpected challenge?

LKM: Yes, originally, we were going to spend this past summer in Alaska to generate data on microbial communities to test our models against. Instead, we’ll have to generate the model first in the lab using measurements of cultured microbes, and then we will test it against the field data next summer. 

Fortunately, we have been able to mine existing genomic data to understand more about the distribution of carbonic anhydrase – our photosynthetic enzyme of interest – in microbes and environments to start creating the scaffolding for our model. Additionally, we have been designing and constructing a custom sampling system that will allow us to measure gas uptake by the fungal cultures maintained in the U’Ren lab. 

The Alaska field station is under immense stress to help continue science in the face of the pandemic, and we felt relatively comfortable changing the order of our plans, and still expect to accomplish all our goals. We hope we will have the green light to sample next summer, and that the spectacular views and science will make up for the delay. 

Why did you choose Alaska as the field site for this project? 

JMU: I have been working on plant- and lichen-associated fungal communities in the boreal and tundra biomes since 2008, when I did my first fieldwork in Alaska. I’ve continued to focus on these environments because they are among the most threatened due to climate change. 

Warming due to climate change is already impacting the biodiversity and species composition in boreal forests, which is predicted to have substantial downstream effects on the net carbon balance and climate feedback effects. To address how symbiotic microbes might help plants mitigate climate stress, we first need to understand their distributions across different plant communities in these endangered high latitude ecosystems like those in Alaska.

Dr. Meredith, have you also traveled to Alaska before, either for work or pleasure?

LKM: I took a field course in Arctic science where we took classes and did small projects at University of Alaska Fairbanks and Toolik Field Station. I was fascinated by the landscape and compelled by its importance and vulnerability in global change science. I have always wanted to return to conduct research. 

Your work centers around carbonyl sulfide (OCS) and carbon dioxide (CO2), but what exactly is OCS, and where does it come from? Why did you choose to study OCS as opposed to CO2 uptake by plants and soil microbes?

LKM: Tracers for photosynthesis are needed to separate the two main carbon cycling processes in terrestrial ecosystems: photosynthesis and respiration. These processes can be extremely hard to distinguish by measurements of CO2 alone because the gas is both produced and consumed, sometimes at the same time and location, in the ecosystem.

Carbonyl sulfide (OCS) is a volatile sulfur gas that is mainly released from the ocean. It’s structurally similar to CO2 (O=C=S vs O=C=O) but is present in the atmosphere at much lower abundances – about 1 million times lower. 

Because this gas acts similarly to CO2 in the photosynthetic processes of plants, it’s a good tracer. Both molecules enter plant leaves through pores – stomata – on the surfaces of plant leaves. As structural cousins, both molecules react with carbonic anhydrase, the first enzyme in the photosynthesis process. The rate that OCS is taken up by leaves is proportional to the rate of CO2 uptake due to photosynthesis, meaning you can measure OCS uptake as a tracer for CO2 photosynthesis. This is the attraction for OCS: we measure leaf or ecosystem OCS uptake and deduce CO2 photosynthetic rates—separating these from respiration rates.

While OCS is not released during respiration, soil microbes with the same photosynthetic enzyme can also take up atmospheric OCS. These soil fluxes have been measured in various biomes around the world but have yet to be characterized in higher altitudes such as the boreal and tundra regions of Alaska. Therefore, we aim to characterize the soil fluxes of OCS in northern regions to enable the use of the gas as an atmospheric trace for carbon cycling in Alaska.

With the knowledge gathered from this project, you aim to better constrain the roles of plants and soil microbes on the overall carbon budget – why is it important to do so?

LKM: Atmospheric CO2 uptake by photosynthesis and release by respiration are the most important processes affecting atmospheric CO2 from the terrestrial biosphere – ecosystems releasing almost 100 times more CO2 than direct manmade emissions. 

Shifts in the delicate balance between photosynthesis and respiration can dictate whether climate change feedbacks worsen.

The Arctic is warming faster than any other region on earth, and there are major questions regarding how much carbon loss will occur from these immense soil carbon reservoirs. Atmospheric measurements of OCS already exist in Alaska that we can use to understand the fate of carbon in these ecosystems based on the balance between photosynthesis and respiration. We will add what we learn on soil OCS uptake to a Simple Biosphere Model that will help us use OCS as a tracer to understand ecosystem CO2 uptake and release.

Dr. Meredith, you’re also the Director of Rainforest Research at Biosphere 2 – you plan to develop education and outreach materials on high latitude ecosystems like Alaska for the facility, correct? Where does your passion for disseminating information on this type of ecosystem to the public stem from?

LKM: By emulating earth’s ecosystems, Biosphere 2 (B2) contains tangible models with vivid stories that help visitors from the general public better understand ecosystems and their underlying processes. B2 is incredibly sensitive to the breathing of plants, providing a great launching point to talk about the difficulty of separating the underlying photosynthetic and respiration processes. 

Representing an arctic ecosystem under the glass in the hot Sonoran Desert is clearly infeasible. Since high latitude ecosystems are currently missing from the B2 experience, we thought that it would be the perfect place to teach visitors about these special ecosystems, their vulnerability to global change, and ongoing research activities to understand them. We can also connect these high latitude biomes to our local "Sky Islands", which harbor the same species of plants as boreal forests in Alaska. 

When you’re not getting your hands dirty or working on education and outreach efforts, what hobbies bring you the most joy?

LKM: I love yoga, hiking, playing with my dog Liebe and cat Rocky, and gardening with the unique flora of the Sonoran Desert. 

JMU: Outside of work, I really enjoy hiking and camping with my family in the Sky Islands.