PhD position “Effects of silicic acid decline on Arctic phytoplankton and sea-ice algae” (SiDeEFFECT) – Deadline 24 November 2022


The research section ‘Polar Biological Oceanography’ in Bremerhaven, Germany, offers a PhD position (m/f/d) within the “Silicic acid Decline Effect on Arctic Marine Ecosystems” (SiDe-EFFECT) Helmholtz Young Investigator Group starting 01.01.2023. Your focus will be on the effect of silicic acid decline on phytoplankton and sea-ice algae carbon and nutrient uptake rates and biodiversity in the Eurasian Basin of the Arctic Ocean.

The overarching objective of SiDe-EFFECT is to understand the reaction mechanisms and the consequences of declining silicic acid input to the Arctic Ocean from an ecosystem perspective, combining physiological response studies of natural communities and individual species, and changes in biodiversity, with grazing interaction experiments, and implementation of new parameterizations in biogeochemical models to improve predictions of the fate of the biological carbon pump in the Eurasian part of the AO.
Specifically, you will investigate the photosynthetic response of microalgal (phytoplankton and sea-ice algae) natural assemblages to different light and nutrient conditions, and the effect of silicic acid decline on the relative abundance of different microalgal taxa, their elemental composition (stoichiometry) and their degree of silicification.


  • Planning and conducting primary productivity measurements in the water column and sea ice of the Arctic Ocean during sea-going expeditions. Perform photosynthesis vs irradiance vs nutrient surfaces (PIN surfaces) using a combination of three stable isotope labelled substrates to measure carbon (13C-sodium bicarbonate), nitrate (15N-potassium nitrate) and silicic acid (30Si-silicic acid).
  • Link microalgal identity with activity by taking subsamples from the stable isotope labelled substrate incubations and analyze the isotope´s incorporation by individual microalgal cells using secondary ion mass spectrometry (SIMS).
  • Identify the groups and species favored by lower silica concentrations and quantify the degree of silicification of key diatoms species under a range of silicic acid concentrations using the Imaging Flow Cytometer.
  • Analyze the elemental composition and carbon to nutrient ratios of different species under different silicic acid concentrations.
  • Merging and analyzing the retrieved data, publishing of results.


  • MSc. in biology, environmental sciences, marine ecosystem managment or related disciplines.
  • Strong interest in method development.
  • Field work experience.
  • Basic phytoplankton knowledge.
  • Experience in data analysis and good computer software skills.
  • High interest in collaborative research, presentation and publication of scientific data.
  • very good English language skills written and spoken
  • Capacity for teamwork, international, inter- and transdisciplinary collaboration.
  • Interest to support and supervise Master-students and interns.
  • Willingness and capability to participate in seagoing expeditions for several weeks.

Further Information

Please contact Dr. Mar Fernàndez-Méndez (; +49(471)4831-1895)  for further information.

This position is limited to 3 years. It is also suitable for part-time employment. The salary will be paid in accordance with the Collective Agreement for the Public Service of the Federation (Tarifvertrag des öffentlichen Dienstes, TVöD Bund), up to salary level 13 (66%). The place of employment will be Bremerhaven.

All doctoral candidates will be members of AWI’s postgraduate program POLMAR or another graduate school and thus benefit from a comprehensive training program and extensive support measures.

The AWI is characterised by

  • our scientific success – excellent research
  • collaboration and cooperation – intra-institute, national and international, interdisciplinary
  • opportunities to develop – on the job, aiming at other positions and beyond AWI
  • a culture of reconciling work and family – an audited and well-supported aspect of our operation
  • our outstanding research infrastructure – ships, stations, aircraft, laboratories and more
  • an international environment – everyday contacts with people from all over the world
  • having an influence – fundamental research with social and political relevance
  • flat hierarchies – facilitating freedom and responsibility
  • exciting science topics, with opportunities also in technology, administration and infrastructure

Equal opportunities are an integral part of our personnel policy. The AWI aims to increase the number of female employees and therefore strongly encourages qualified women to apply.

Disabled applicants will be given preference when equal qualifications are present.

The AWI fosters the compatibility of work and family in various ways and has received a number of awards as a result of this engagement.

We look forward to your application!

Please submit your application by November 24th 2022, exclusively online.
Reference number 22/172/G/Bio-b

Further information can be found here.

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