The trial lecture is: "Where, when, and why is organic matter degraded and accumulated?".
Time and place: November 4, 2022 10:15 AM, Nucleus, Bikuben, The Kristine Bonnevie building.
Main research findings
Many lakes worldwide are supersaturated with CO2, making them net emitters of CO2 to the atmosphere. In order to predict the future and be able to mitigate the effects of climate change, knowledge of the processes behind increased CO2 saturation is crucial. I found that the amount of organic carbon of terrestrial origin in lakes is the main regulator of CO2 production and that the dominating process is bacterial respiration, increasing with increasing amounts of organic carbon. I also found that this is not necessarily the case in all lakes. The amount of coniferous forest in the catchment has a key role in this coupling between organic carbon and bacterial respiration. Because of climate and environmental change, an increasing amount of organic carbon from the surrounding ecosystems enters lakes. While bacteria use this carbon as energy source, it is also brown to its colour and therefore shades algae and inhibits photosynthesis. In this way, the productivity of the lake may be affected, having implications throughout the entire food web, affecting all from microorganisms to predating fish.
Adjudication committee
Professor Lars Tranvik, Uppsala University
Professor Emma Kritzberg, Lund University
Professor Stein Fredriksen, University of Oslo
Chair of defence
Professor Stein Kaartvedt, University of Oslo
Supervisors
Professor Dag Olav Hessen, University of Oslo
Professor Tom Andersen, University of Oslo
Professor Josefin Titelman, University of Oslo