Postdoc: Ocean Acidification & the Marine Phosphorus Cycle

Utrecht University; Netherlands; On-site; EUR 41,000 - 64,000; Full time

Benefits offered by this job

36-40 hour work week

Holiday pay 8%

Year-end bonus 8.3%

Pension scheme

Flexible terms of employment

Personal and professional growth

Job summary

Utrecht University seeks a highly motivated postdoctoral researcher to model phosphorus dynamics in sinking marine snow and CaCO3 interactions within the PHOSFLUX project. You will develop reactive-transport models and test them against laboratory and field data, collaborating closely with a PhD student and a UU postdoctoral researcher.

The role requires a PhD in Earth or environmental sciences or a related field, strong modelling skills, and willingness to travel for synchrotron beam times.

Qualifications

• PhD required by start date.
• Background in Earth Sciences, Environmental Sciences, Biology or related field.

Responsibilities

• Build a reactive-transport model for P dynamics in marine snow and CaCO3 interactions.
• Test model predictions against experimental and field data from PHOSFLUX.
• Collaborate with PhD student and UU postdoctoral researcher on modelling efforts.

Skills

Biogeochemical modelling

Numerical modelling

Synchrotron analysis

English language

Team player

Education

PhD completed

Earth/Environmental/Biology backgrounds

Job description

Organisation/Company Utrecht University Research Field Environmental science » Earth science Environmental science » Global change Researcher Profile Recognised Researcher (R2) Application Deadline 31 Oct 2026 - 22:59 (UTC) Country Netherlands Type of Contract Temporary Job Status Not Applicable Hours Per Week 40.0 Is the job funded through the EU Research Framework Programme? Not funded by a EU programme Is the Job related to staff position within a Research Infrastructure? No

Offer Description

Microscopic calcite (CaCO3) shells of plankton sink through ocean waters to the seafloor by the trillions each year, taking along essential nutrients such as phosphorus (P). Ocean acidification is likely to alter global CaCO3 fluxes, with so far unknown consequences for P cycling, ocean fertility and CO2 uptake. Our lack of knowledge regarding these feedbacks limits our insight in ocean functioning under environmental change, both in the (ancient) past and the human-impacted future.

Your job

The NWO-funded PHOSFLUX project aims to shed light on these unknowns, by quantifying the role of CaCO3 fluxes and acidification in global marine P cycling through a combination of field work in the North Atlantic Ocean, laboratory experiments and numerical modelling. A scientific cruise with our research vessel Pelagia will allow us to investigate CaCO3 – P interactions in the field. Through controlled lab experiments, we will dive deeper into the underlying chemical and mineralogical processes, to eventually capture them in physical-chemical models that predict the impact of acidification on marine P cycling.

The PHOSFLUX project is a collaboration between the NIOZ (dr. Peter Kraal) and Utrecht University (UU; prof. dr. Mariëtte Wolthers), combining unique sea-going and on-shore experimentation with advanced analytical tools to understand mineral-water interactions from microscopic to ocean-basin scale. Besides PI’s Kraal and Wolthers, the PHOSFLUX team consists of a NIOZ-based PhD student performing experiments and analyses, and a UU-based postdoctoral researcher who focuses on modelling the CaCO3 – P interactions.

As postdoctoral researcher within PHOSFLUX, your role is to model P dynamics in sinking and deposited marine snow in relation to changing environmental conditions in the water column. To achieve this, you will create a reactive-transport model for P dynamics that will include processes such as CaCO3 dissolution, organic matter decomposition and adsorption/incorporation of PO4 into solid phases of marine snow. You will test the performance of your model by simulating experimental and field data in collaboration with the PHOSFLUX PhD student.

We are looking for a highly motivated postdoctoral candidate with a background in biogeochemical modelling.

You must have successfully completed a PhD programme in Earth Sciences, Environmental Sciences, Biology or a related discipline by the time the position starts. Preferably, you also have:

• Experience and affinity with biogeochemistry and marine research;
• Experience in numerical modelling of mineral-water interactions and/or organic matter degradation processes;
• Experience or strong interest in synchrotron-based analysis techniques

You approach scientific problems with determination and are eager to develop multidisciplinary skills. You must be willing to travel abroad to join the PHOSFLUX team during synchrotron beamtimes and to present your research to an international research community. As this project requires close collaboration within the research team, candidates are expected to be excellent team players. You also have excellent written and spoken English skills and good general communicational skills. We highly encourage applicants from diverse backgrounds to join us.

Additional Information

We offer:

• a position (1.0 FTE) for 36 months.
• a working week of 36 - 40 hours and a gross monthly salary between €3.706 and €5.760 (salary scale 10 under the Collective Labour Agreement for Dutch Universities (CAO NU)). The salary is based on a 38-hour working week;
• 8% holiday pay and 8.3% year-end bonus;
• a pension scheme, partially paid parental leave and flexible terms of employment based on the CAO NU.

In addition to the terms of employment set out in our collective labour agreement, we offer attractive additional benefits, including opportunities for personal and professional growth , flexible leave arrangements, and extra vacation days. Through the UU Terms of Employment Options Model, you can tailor your employment package to your needs. In this way, we encourage you to grow in what you do, both in your work and in your development. Read more about our terms of employment .

Selection process

At Utrecht University, we strive to be a place where everyone feels at home. We value colleagues with different backgrounds, perspectives and identities, including differences in culture, religion or ethnicity, gender, sexual orientation, neurodiversity, disability and age. We are committed to creating a safe and inclusive environment where everyone can thrive and contribute. Read more about our commitment to diversity and inclusion. If you have any questions about accessibility, for example regarding your workplace Vening Meineszgebouw A , the application process or your work, please contact us via our HR contact page .

Knowledge security screening can be part of the selection procedures of academic staff. We do this, among other things, to prevent the unwanted transfer of sensitive knowledge and technology.

The position can start as soon as possible and ultimately by 1January 2027.

Note that international candidates that need a visa/work permit for the Netherlands require at least four months processing time after selection and acceptance. This will be arranged with help of the International Service Desk (ISD) of our university. Finding appropriate housing in or near Utrecht is your own responsibility, but the ISD may be able to advise you therewith. In case of general questions about working and living in The Netherlands, please consult the Dutch Mobility Portal .

For informal information (not for application) about this position, please contact Prof. Dr Mariëtte Wolthers at [e-mail]

Candidates for this vacancy will be recruited by Utrecht University.