Margot Debyser

Nutrient Cycling in the Arctic and Subarctic Oceans: A Stable Isotope Study

This PhD was hosted in the School of GeoSciences, University of Edinburgh, in partnership with the Scottish Association for Marine Science.

I feel like I have learnt a lot about myself, and I have really grown both as a person and a scientist.

What was your research about?

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Margot during a research oceanographic cruise in Greenland
Margot during a research oceanographic cruise in Greenland

Around half of all photosynthesis on our planet happens in the oceans. Photosynthesis is carried out by algae in surface waters, which need nutrients to grow. Global warming in the Arctic regions and the North Atlantic is affecting the supply of these essential nutrients to the surface ocean. Algae are the base of the marine food chain, and their future is uncertain under current climate change scenarios.

My PhD examined the sources of two vital nutrients, nitrate and silicic acid, to the Arctic Ocean and the North Atlantic. Arctic rivers are found to be an important source of silicic acid to the Arctic Ocean. Biological activity controls the distribution of nutrients in the Arctic. Low concentrations of nitrate in the coastal seas of the Arctic limit biological activity, which allows silicic acid to leak out of the Arctic Ocean into the North Atlantic. As river discharge increases because of climate change, an increasing amount of silicic acid is expected to be transported out of the Arctic Ocean.

In the Atlantic Ocean, recent freshening events have reduced biological activity in surface waters, with far-reaching impacts to the Arctic regions and deep waters of the North Atlantic. The results from this research can be used to understand how humans have impacted algae growth in our oceans and to predict how Arctic and North Atlantic marine food chains will be impacted in the future.

What made you apply to the E3 DTP?

The opportunity for fieldwork in the Arctic Ocean and getting to work on climate change in remote regions.

What did you find challenging in your PhD?

The two years of COVID during the middle years of my PhD definitely created an additional challenge and made the PhD process a lot lonelier than I expected. There were many ups and downs, it was mentally challenging and required a lot of resilience. I can’t say I would do another PhD, but I am really glad I did this. I feel like I have learnt a lot about myself, and I have really grown both as a person and a scientist.

Looking back, what would you have done differently?

I would have made more efforts to reach out to other PhD students and staff members during COVID years so it would feel less isolating, perhaps explore more online training options.

Which aspects of your PhD did you enjoy the most?

The fieldwork opportunities I have had in the Arctic Ocean and the Southern Ocean. These are such intense experiences in remote areas of the world’s oceans, which have made me feel tightly connected to the world of oceanography ever since. During my PhD, I also was given a lot of time and received a lot of expert advice for using the mass spectrometry facilities at Edinburgh, which have been very valuable skills when applying for a postdoc.

PhD Highlights

  • Oceanographic research cruises in the Arctic Ocean with the Norwegian Polar Institute – between Svalbard and Greenland

  • Travelling around the UK and Europe for conferences and getting to meet oceanographers and other scientists in person

  • Developing a method for and using the MC-ICP-MS of the Price Laboratory at the University of Edinburgh

Which skills did you gain during your PhD?

I became an independent researcher, with skills like critical and creative thinking, resilience, perseverance and communication.

I was also surprised by the amount of creativity research involves – these aspects of academia I really enjoy and have made me want to pursue a career in research.

How has your PhD helped you to decide on a career path?

I really enjoy the variety of work linked to research from field to lab and office. I was also surprised by the amount of creativity research involves – these aspects of academia I really enjoy and have made me want to pursue a career in research.

And now?

I have now started a postdoc at Woods Hole Oceanographic Institute, working on isotopes in the South Pacific Ocean through the GEOTRACES programme. I applied for it in March/April and have moved over to the U.S. at the start of September to help preparing for our cruise in November.