PhD Mixotrophy as a winter survival strategy in Arctic phytoplankton

Do you have a keen interest in marine microbial ecology? Are you interested in the dynamics of phytoplankton communities, and how they are affected by environmental change? Do you like to combine laboratory experiments with molecular methods and fieldwork in polar ecosystems? Apply for this vacancy and start your PhD research.

About the position
In the Arctic Ocean, photosynthetic phytoplankton face a major energetic bottleneck during winter: they must survive several months of darkness during the polar night. Many polar phytoplankton species remain physiologically active during this time, which seems to be made possible by two main overwintering strategies: reliance on storage compounds accompanied by a downregulation of respiration, and a switch to heterotrophic utilization of organic compounds (osmotrophy) or microbial prey (phagotrophy). The fast rate of climate warming in the Arctic is expected to further challenge phytoplankton winter survival, as the higher metabolic rates at higher temperatures might deplete energy reserves faster. This can cause a stronger dependence on heterotrophic carbon acquisition, yet this is the least well understood survival mechanism. The SURPHYVE project is a collaboration between the University of Amsterdam (UvA), the Royal Netherlands Institute of Sea Research (NIOZ) and the Alfred Wegener Institute (AWI), and will assess the mechanisms underlying Arctic phytoplankton winter survival under current and warming conditions. This PhD position will focus on the role of phagotrophy in phytoplankton winter survival and involve laboratory experiments, winter fieldwork, and analysis of transcriptomic datasets.

What are you going to do?
As PhD student in the SURPHYVE project you will investigate how feeding on bacteria contributes to phytoplankton winter survival by performing grazing rate measurements and assessing gene expression in natural winter communities, and by assessing the temperature dependence of phytoplankton resource (nutrients, carbon, bacterial prey) requirements in laboratory experiments.

This PhD position is tightly linked to two postdoc positions within the SURPHYVE project, which will focus on the role of osmotrophy and rates of mortality in shaping winter survival, respectively. The fieldwork and some of the experiments will be performed as a team, while the PhD student will also perform laboratory experiments on their own.

Training and courses during the PhD trajectory will be offered by UvA, and by the Graduate School for Production Ecology & Resource Conservation (PE&RC).

Tasks and responsibilities:

• Conducting laboratory experiments with cultured phytoplankton strains to assess their physiological responses under controlled conditions;
• Participation in research expeditions to Svalbard, to assess phytoplankton species composition and perform field experiments to quantify their feeding rates;
• Analysis of data from laboratory experiments and field expeditions, and publication of results in international scientific journals;
• Presentation of the results in the department, at meetings of the Netherlands Polar Program, and at (international) scientific conferences;
• Supervision of BSc and/or MSc students who wish to do an internship on Arctic phytoplankton and assistance in BSc or MSc courses;
• Completion of a PhD thesis within the official appointment duration of four years.

Your profile
We are looking for an enthusiastic candidate, who enjoys a combination of laboratory experiments, field studies and data analysis. You have a keen interest in marine phytoplankton ecology and are eager to perform research in polar ecosystems. You enjoy working in a team, but are also able to work independently and stay well-organized when it gets busy.

Your experience and profile:

• A MSc degree in marine biology, microbial ecology, biological oceanography, or closely related discipline;
• Experience with culturing of bacteria or phytoplankton in the laboratory, and/or with field research in marine and/or freshwater ecosystems;
• Willingness and ability to perform winter fieldwork on Svalbard;
• Strong communication and writing skills in English;
• A demonstrated ability to work with programming software such us R or Python is a plus;
• Experience with statistical analysis of large dataset and/or bioinformatics is a plus;
• Holding a driving license B is beneficial.

Techniques to be used in this research include, e.g. flow cytometry, (fluorescence) microscopy, PAM-fluorometry, isotope analysis, and proteomics. We do not expect that candidates master all these techniques from the start, but consider previous experience with one or more of these as an advantage.

Our offer
A temporary contract for 38 hours per week for the duration of 4 years (the initial contract will be for a period of 18 months and after satisfactory evaluation it will be extended for a total duration of 4 years). This should lead to a dissertation (PhD thesis). We will draft an educational plan that includes attendance of courses and (international) meetings. We also expect you to assist in teaching undergraduates and master students. The preferred starting date is Spring 2026.

For this position the University Job Classification profile “Promovendus” (PhD candidate) applies. Your salary will be € 3,059 gross per month in the first year and will increase to € 3,881 in the final year, based on full-time employment of 38 hours per week. In addition, you will receive an 8% holiday allowance and 8.3% year-end allowance.

A favourable tax agreement, the ‘30% ruling’, may apply to non-Dutch applicants.

The Collective Labour Agreement of Universities of the Netherlands is applicable.

Besides the salary and a vibrant and challenging environment at Science Park we offer you multiple fringe benefits:

• 232 holiday hours per year (based on fulltime) and extra holidays between Christmas and 1 January;
• multiple courses to follow from our Teaching and Learning Centre;
• a complete educational program for PhD students;
• multiple courses on topics such as time management, handling stress and an online learning platform with 100+ different courses;
• 7 weeks birth leave (partner leave) with 100% salary;
• partly paid parental leave;
• the possibility to set up a workplace at home;
• a pension at ABP for which UvA pays two third part of the contribution;
• the possibility to follow courses to learn Dutch;
• help with registration at UvA- Housing for a studio or small apartment when you’re moving from abroad.

Are you curious to read more about our extensive package of secondary employment benefits, take a look here.

About us
The Institute for Biodiversity and Ecosystem Dynamics (IBED) is one of eight research institutes of the Faculty of Science at the University of Amsterdam. The research at IBED aims to unravel how ecosystems function in all their complexity, and how they change due to natural processes and human activities. At its core lies an integrated systems approach to study biodiversity, ecosystems and the environment. IBED adopts this systems approach to ecosystems, addressing abiotic (soil and water quality) and biotic factors (ecology and evolution of plants, animals, and microorganisms), and the interplay between those. The IBED vision includes research encompassing experimental and theoretical approaches at a wide variety of temporal and spatial scales, i.e. from molecules and microorganisms to patterns and processes occurring at the global scale. The University of Amsterdam has excellent high performance computing facilities. Furthermore, IBED has a dedicated computational support team with specialized knowledge of bioinformatics, (geo)database management and scientific programming. IBED also works with non-academic partners to deliver transdisciplinary science for society.

The position will be based in the Department of Freshwater and Marine Ecology, which aims to increase our understanding of the biodiversity and dynamics of freshwater and marine ecosystems from the level of molecules and genes to entire ecosystems. The departments objective is to unravel how aquatic ecosystems function in all their complexity, and how they change due to natural processes and human activities. The focus lies on the interactions between aquatic organisms and their abiotic environment, including their role in biogeochemical cycles and the temporal and spatial dynamics that emerge from these interactions.

Want to know more about our organisation? Read more about working at the University of Amsterdam.

If you feel the profile fits you, and you are interested in the job, we look forward to receiving your application. You can apply online via the ‘Apply’-button on the vacancy’s webpage. We accept applications until and including 15 January 2026.

Applications should include the following information (all files besides your cv should be submitted in one single pdf file):

• a detailed CV including the months (not just years) when referring to your education and work experience;
• a letter of motivation (max. one page);
• the names and email addresses of two references who can provide letters of recommendation.

Only complete applications received within the response period via the link below will be considered.

A knowledge security check can be part of the selection procedure. (for details: national knowledge security guidelines)

We will invite potential candidates for interviews soon after the closing date. A first round of online interviews will be held on January 26th, followed by in-person interviews on February 12th.

Do you have any questions, or do you require additional information? Please contact:

Dr. Susanne Wilken, s.wilken@uva.nl