Sigrún Jónasdóttir. Foto: Joachim Rode.

Doctoral thesis on fatty acids in marine ecosystems

Thursday 12 Nov 15


Sigrun Jonasdottir
Senior Researcher
DTU Aqua
+4535 88 34 27

About the defence

Time & place 
Sigrún Jónasdóttir will be defending her thesis ”A Journey from Light into Darkness. Fatty Acids in the Marine Ecosystem: from Photosynthesis to Copepod Lipids and Sequestration” on Friday, 13 November at 2 p.m. in meeting room 1, building 101, at DTU, Anker Engelundsvej 1, 2800 Kgs. Lyngby, Denmark.

Assesment committee 
The opponents are Professor David Chekley, Scripps Institute of Oceanography, UC San Diego, and Professor Richard Lee, Skidaway Institute of Oceanography, University of Georgia.

Both opponents have been appointed by DTU and have been on the assessment committee together with the chairman of the committee, Professor Brian MacKenzie, DTU Aqua, who is also appointed by DTU.

Executive Vice President, Provost Henrik Wegener, DTU, is the moderator for the defence.

Thesis copy 
A copy of the thesis can be obtained from Sigrún Jónasdóttir,

Senior Research Scientist Sigrún Jónasdóttir will be defending her doctoral thesis on copepods at DTU—Technical University of Denmark. Not only do copepods ensure that we can get vital omega-3 fatty acids, they also remove large amounts of carbon dioxide from the atmosphere.

Most people have probably heard that fish contains healthy fatty acids, but probably not many are aware that this is due to copepods. Copepods are among the largest groups of zooplankton in the sea and are the key vehicle for transporting omega-3 fatty acids through the marine food webs. They feed on phytoplankton that produce organic matter with the aid of sunlight, and are in turn eaten by fish, birds, and whales.

The importance of fatty acids in the marine ecosystem and the role of copepods have been Sigrún Jónasdóttir’s research area since she was a PhD student at the State University of New York in the beginning of the 1990s. Along with 19 other scientific articles, her first scientific article from that period now forms the basis for the doctoral thesis she will be defending at DTU on 13 November 2015. 

Upon the successful defence of her thesis and the approval from Academic Council, Sigrún Jónasdóttir will be awarded the technical doctoral degree—Dr. Techn.—the highest Danish academic award in engineering and technical scientific research.

Combining biology and chemistry

Sigrún Jónasdóttir comes from Iceland, where she earned her BSc in biology from the University of Iceland in 1984. Back then, it was not possible to take an MSc in biology in Iceland, and therefore she continued at the University of Washington in Seattle, USA, where she completed an MSc in oceanography, which, in addition to biology, also includes chemistry and physics. This marked the beginning of the interdisciplinary approach involving biology and chemistry on which Sigrún Jónasdóttir has based her research ever since.

She met her husband André W. Visser when she was a PhD student in New York. It took them a few years to find a job in the same country, but succeeded to settle in Denmark, where Sigrún Jónasdóttir was affiliated with DTU Aqua (then the Danish Institute for Fisheries Research) as postdoc in 1993. In 1998, she became senior research scientist at DTU Aqua, where her husband is today a professor of physical oceanography.

Sigrún Jónasdóttir’s research is, to a large extent, based on the data which she has collected in the North Atlantic over the years, for example from DTU's marine research vessel, Dana.

Ground-breaking discovery

In 2014, Sigrún Jónasdóttir’s research took a new turn. She wanted to calculate the impact of the overwintering of copepods in deep water on the ocean’s uptake of carbon from the atmosphere. The surprising result of her study has led to a revision of our understanding of the global carbon cycle.

Each year, copepods descend to great depth in the ocean basins for overwintering, where they survive on their fat reserves. When burning fat, they respire carbon dioxide. This carbon dioxide remains trapped in the deep waters of the oceans for up to 1,000 years. The copepod species (Calanus finmarchicus), that Sigrún Jónasdóttir has studied, alone actively moves 1-3 tonnes of carbon from the surface of the North Atlantic each year in connection with its overwintering and thus removes a similar amount of carbon dioxide from the atmosphere. 

The Icelandic connection

Sigrún Jónasdóttir has maintained her professional connection to Iceland over the years. From 2005 to 2009, she was a member of the Icelandic Marine Research Institute’s advisory board, and she has, among other things, organized courses for international PhD students in Iceland. 

Privately, she is a board member of the Icelandic cultural centre in Denmark, Jónshús, and she also sings in the Icelandic chamber choir Staka. 

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