Tobias Vonnahme » Members

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Tobias Vonnahme

PhD candidate UiT The Arctic University of NorwayArctic and Marine Biology
Work address Department of Arctic and Marine Biology Faculty of Biosciences, Fisheries and Economics UiT The Arctic University of Norway Tromsø 9037 Norway Work Phone: +47 77 64 48 28 Website: UiT profile Website: Arctic SIZE project Website: google scholar profile
Photo of Tobias Vonnahme

PhD project title:

Microbial carbon cycling in the seasonal ice zone: linking observations and experiments to dynamic modelling

Project description:

The carbon cycle in the seasonal ice zone is highly dynamic over the year and and in a changing climate. Light limitations in the polar night, ice formation and melt, and nutrient limitations are some of these dynamic factors. Dynamic ecosystem models are still neglecting these dynamics and the physiological mechanisms of algae and bacteria to deal with it. The aim of my PhD is to study Three important processes in the microbial carbon cycle in the seasonal ice zone which are poorly characterized in current ecosystem models; 1) heterotrophic carbon uptake in microalgae as response to light and nutrient limitation, also as potential survial strategy in the polar night; 2) The role of bacteria as competitors or commensalists via nutrient recycling under different light and nutrient conditions; 3) The role of tidewater outlet glaciers on microbial communities and their function in the ecosystem.  I will quantify the role of the Three processes in the carbon cycle and show their importance in dynamic ecosystem models. The results will help to understand the importance of key processs and to improve predictions on the effect of climate change on the  carbon cycle.

Start date: March 2017
Planned submission date: March 2020


Rolf Gradinger (UiT – The Arctic University of Norway, Tromsø, Norway)

Dick van Oevelen (NIOZ – Royal Netherlands Institute for Sea Research, Netherlands)

Tron Frede Thingstad (UiB – The University of Bergen, Norway),

Geir Johnsen (NTNU – Norwegian University of Science and Technology, Trondheim, Norway)

Relevant scientific publications:

  1. Vonnahme, T. R., Devetter, M., Žárský, J. D., Šabacká, M., & Elster, J. (2016). Controls on microalgal community structures in cryoconite holes upon high-Arctic glaciers, Svalbard. Biogeosciences, 13(3), 659-674. doi:10.5194/bg-13-659-2016
  2. Zawierucha, K., Ostrowska, M., Vonnahme, T.R., Devetter, A.M., Nawrot, P., Lehmann, S., Kolicka, M. (2016). Diversity and distribution of Tardigrada in Arctic cryoconite holes, Journal of Limnology. doi: 10.4081/jlimnol.2016.1453
  3. Zawierucha, K., Vonnahme, T.R., Devetter, M., Kolicka, M., Ostrowska, M., Chmielewski, S., Kosicki, J.Z. (2016). Area, depth and elevation of cryoconite holes in the Arctic do not influence Tardigrada densities, Polish Polar Research, 37(2), 325-334. doi: 10.1515/popore-2016-0009l
  4. Vonnahme, T. (2014). Microbial community structure in cryoconite holes in high Arctic glaciers on Svalbard, Bachelor thesis
  5. Vonnahme, T.R. (2016). Microbial diversity and function of deep sea manganese nodule ecosystems, Master thesis

Popular outreach (excl. conferences):

  • Arctic Frontiers 2018, Tromsø, Norway, Pecha Kucha Talk: Modelling climate change in the Arctic