Background

In the Southern Ocean the input of the trace metal iron (Fe) is the primary control of phytoplankton productivity, thus affecting the biological CO2 uptake of the Southern Ocean. Externally sourced contributions of new Fe to SO surface waters are thought to be low, which suggests that recycling within the system is an important mechanism for supplying Fe to Antarctic phytoplankton. Animals recycle Fe through their diet and subsequent defecation. Taking into account the population sizes of whales, seals, and seabirds in the Southern Ocean, their collective Fe input is considered fundamental for the Southern Ocean ecosystem. However, Fe recycling by these animals represents an important, but not well quantified pathway to supply Fe to pelagic phytoplankton. Currently, there are no investigations that looked at the bioavailability of the released Fe by large animals (e.g., whales, seals, flying seabirds), which directly measured its influence on Southern Ocean phytoplankton productivity and the potential for carbon export. Hence, an assessment of the impact of Antarctic animals as potential Fe fertilizers is urgently required. In this project, we will concentrate on Antarctic animals, which are of major ecological relevance in the Antarctic ecosystem and that potentially act as local Fe fertilizers of the remote Fe-poor Southern Ocean waters. The main research objectives in the proposed research project will be to investigate the fertilization effect of their feces on Southern Ocean phytoplankton productivity in laboratory experiments and to perform phytoplankton incubation studies during the Polarstern cruise KrillBIS scheduled for 2027 (February-April). This will allow to obtain a better understanding on the importance of whales, seals, and flying seabirds in sustaining Southern Ocean productivity and will give more insights on their impact on the biological carbon pump. The main objectives of this research project will be:

(1) Quantifying Fe release of the fecal material of whales, seals and seabirds into seawater and their Fe bioavailability to Antarctic key phytoplankton species in laboratory and field experiments.

(2) Assessing the fertilizing effect of each fecal material on growth and carbon fixation on Antarctic phytoplankton in field experiments.

(3) Determining the carbon export potential of phytoplankton after fecal Fe fertilization.


Requirements

Essential requirements of the candidate

Completed scientific university degree (Master/University diploma or comparable) in biology, marine biology, marine chemistry, environmental sciences or natural sciences

Participation in a field expedition to the Western Antarctic Peninsula onboard of RV Polarstern

English language skills (spoken and written).

Ideally, the candidate has experience in:

culturing of marine phytoplankton

trace metal clean work

knowledge of trace metal seawater chemistry

applying methods in algal physiology

participation in sea-going expeditions


The candidate should be highly motivated and have the ability to work in a small, closely cooperating team. The candidate should be willing to participate in a field expedition to the Antarctic onboard of RV Polarstern. Furthermore, good communication and English language skills (spoken and written) are expected.