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Lighting the Way: Metabolic Tracing of Plankton Sugars in Marine Sediments

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Project Description

Marine microbes play a crucial role in transforming organic matter that sinks from the ocean surface to the seafloor, including polysaccharides from plankton, which serve as an important carbon source. Additionally, microbial and faunal glycogen in sediments also contributes to this organic matter resource. However, the dynamics between these two carbon pools—ocean-sourced versus sediment-derived—and their influence on marine microbial communities remain unclear. This project will examine how microbial communities in sediments respond to fresh, plankton-derived sugars and in situ glycogen, using fluorescently labeled polysaccharides as tracers. We will focus on the spatial fate of these sugars and how microbes sense, process, and forage for them across different redox regimes. By analyzing microbial turnover rates of individual sugars and synthetic particles, we will identify glycan degradation mechanisms with attention to laminarin degradation and glycogen turnover throughout the year. We will combine these measurements with determinations of oxygen turnover and nitrogen/sulphur turnover rates using a suite of microsensor and stable/radio isotope techniques. This study builds on advances made during the Phase I and by the Reintjes Lab in identifying and tracking plankton sugars. Ultimately this study aims to clarify the impact of microbial diversity and metabolism on carbon cycling and burial, providing insights into the biological carbon pump's efficiency in a changing ocean.

Further Reading

• Knittel K, Miksch S, Moncada C, Silva-Solar S, Moye J, Amann R, Arnosti C. 2024. Distinct actors drive different mechanisms of biopolymer processing in polar marine coastal sediments. Environmental Microbiology 26:e16687. doi:10.1111/1462-2920.16687
• Moncada C, Arnosti C, Brüwer JD, de Beer D, Amann R, Knittel K. 2024. Niche separation in bacterial communities and activities in porewater, loosely attached, and firmly attached fractions in permeable surface sediments. The ISME Journal 18:wrae159. doi:10.1093/ismejo/wrae159
• Reintjes G, Fuchs BM, Scharfe M, Wiltshire KH, Amann R, Arnosti C. 2020. Short-term changes in polysaccharide utilization mechanisms of marine bacterioplankton during a spring phytoplankton bloom. Environmental Microbiology 22:1884-1900. doi:10.1111/1462-2920.14971.
• Reintjes G, Arnosti C, Fuchs B, Amann R. 2019. Selfish, sharing and scavenging bacteria in the Atlantic Ocean: a biogeographical study of bacterial substrate utilisation. ISME J 13:1119-1132. doi:10.1038/s41396-018-0326-3
• Bourceau OM, Ferdelman T, Lavik G, Mussmann M, Kuypers MMM, Marchant HK. 2023, Simultaneous sulfate and nitrate reduction in coastal sediments, ISME Comm 3:1,17 doi:10.1038/s43705-023-00222-y

Modalities

The doctoral project will be supervised by Hannah Marchant and Greta Reintjes (University of Bremen) within the working group “Microbial-Carbohydrate Interactions” at the MARUM – Center for Marine Environmental Sciences at the University of Bremen The remuneration corresponds to pay group TV-L 13 with 75% of the weekly working hours for a fixed-term period of 4 years, starting January 1st 2026 the earliest and until at most December 31, 2029 (according to § 2 WissZeitVG) with the aim of obtaining a doctorate.

Main Tasks

• Scientific research in the field of:
  Marine Biogeochemistry / Marine Microbiology
  
  
• Analysis of:
  Plankton sugars / Biogeochemical Analyses / Molecular Sequencing / Microscopy / Experimental Design
• Writing of scientific publications
• Participation in ship expeditions
• Participation in international conferences

Formal Requirements:

Completed scientific university degree (Master/University diploma or comparable) in Marine Geosciences, Biological Oceanography, Earth Sciences, Marine Microbiology, Environmental Sciences, or a related discipline.

Further questions?

Questions about the project can be addressed to Hannah Marchant ([Bitte aktivieren Sie Javascript]) or Greta Reintjes ([Bitte aktivieren Sie Javascript]).