Interview:"Understanding the organic matter reactivity in lake sediments could help us predicting methane and CO2 emissions"

In this interview, iC3 intern Léa Pigeolet explains her research on organic carbon reactivity in sediments from proglacial lakes, her interest in Arctic environments and her path towards a career in climate science

Can you briefly describe yourself and the focus of your research?

My name is Léa Pigeolet and I am doing an internship at the iC3 Polar Research Hub with Guillaume Lamarche-Gagnon. There, I am investigating carbon reactivity in sediments from proglacial lakes. These lakes are fed by glacial meltwater. I work mainly with sediment samples from proglacial lakes in Greenland, collected by Joost van Genuchten as part of his PhD thesis, as well as fresh samples that I collected from a proglacial lake in Steindalen near Tromsø. My aim is to understand how organic carbon in these sediments can be transformed by microorganisms and released as greenhouse gases.

Credit: Guillaume Lamarche-Gagnon.

How do you measure carbon reactivity?

I carry out incubation experiments. I place thawed or fresh sediment with water into small bottles, keep them at a chosen temperature, and measure the gases released over time. In anaerobic incubations, without oxygen, I measure methane production. In aerobic incubations, with oxygen, I measure carbon dioxide production. This helps us assess how biologically available, or reactive, the sediment’s organic carbon is.

Why is this research important?

Carbon dioxide and methane are powerful greenhouse gases, so identifying where they come from and how they are produced is essential for improving our understanding of the global carbon and methane budgets. Proglacial lakes are increasingly common in deglaciating regions, and their role in carbon cycling is an active area of research.

What was the benefit of collecting fresh sediments in Steindalen?

Fresh samples are valuable because freezing can disturb microbial communities and affect their activity. By incubating sediments shortly after collection, I can study processes that are closer to their natural state. Fieldwork was also a great opportunity to see the proglacial environment directly and contribute new samples to the dataset.

Credit: Laura Rasmussen.

What did you study during your master’s degree?

I studied bioengineering in Louvain-la-Neuve, Belgium, with a focus on agronomy as well as soil and water resources. I became especially interested in environmental processes, global change, soils and water.

What was your master’s thesis about?

For my master’s thesis, I studied subsea permafrost sediments from the East Siberian Arctic Shelf. I investigated links between iron and organic carbon in the sediments, combining my iron analyses with existing carbon dioxide and methane data from anoxic incubation experiments on the corresponding samples. To achieve this, I performed several iron extractions in the lab and also used the X-ray fluorescence method (XRF).

How is your previous work related to your current internship?

The central carbon processes are similar. In both subsea permafrost and proglacial-lake sediments, microorganisms can use organic carbon and produce carbon dioxide or methane. The environments differ, however: subsea permafrost is beneath the sea and is a strictly anoxic environment, while proglacial lake sediments can have access to some oxygen. I used existing CO2 and CH4 emissions data for my master's thesis, so it's really exciting to be able to carry out this experiment by myself during this internship.

What scientific methods or technologies are you most excited about?

I really enjoy using the anaerobic chamber. It allows me to handle samples in an oxygen-free environment. I put my hands into built-in gloves and work carefully so that I do not disturb the gases inside. It feels a little futuristic—almost like working as an astronaut—and it is a very useful tool for studying methane-producing processes.

Credit: Guillaume Lamarche-Gagnon.

Where do you see yourself after this internship?

I would like to continue working on global change, carbon emissions and Arctic environments. I am interested in glaciers, permafrost, soils and water systems. I hope to begin a PhD and continue exploring how environmental change affects carbon cycling in northern ecosystems.

What does an ideal day off look like for you?

My ideal day off would be to go for a hike in the mountains, spend some time with friends and have a bit of a rest. Tromsø is an amazing place for being outdoors. 

What are you looking forward to next year?

Professionally, I hope to continue in research. Personally, I would like to do a bike trip if I have time before starting. I cycled through Slovenia this summer, and I would love to travel farther in Europe by bike, perhaps even towards Turkey.

Léa Pigeolet is an intern at the iC3 Polar Research Hub, based in the Department of Geosciences at the UiT Arctic University of Norway, Tromsø. To find out more about her work, please contact her by email or via LinkedIn.