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Deep-sea natural petroleum seeps and hydrothermal systems as sources of marine recalcitrant dissolved organic matter

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Project Description

Natural petroleum seeps and hydrothermal systems release and transform dissolved organic matter (DOM) and trace metals, influencing marine biogeochemical cycles. This project will quantify and characterize recalcitrant DOM (RDOM) from petroleum seeps in Arctic Baffin Bay and from reactive oxygen species (ROS)-mediated transformations at Arctic Knipovich Ridge hydrothermal vents.

Petroleum seeps in Baffin Bay may release refractory polycondensed aromatics (dissolved black carbon, DBC) and dissolved organic sulfur (DOS), both key components of oceanic RDOM. At Knipovich Ridge, oxidation of reduced iron and hydrogen sulfide may generate ROS that convert DOM into aromatic-rich RDOM (Shaw et al., 2021; Goranov et al., 2024). While DBC is often attributed to terrestrial sources (Dittmar et al., 2021), recent studies confirm marine DBC and DOS inputs from seeps and hydrothermal systems (Brünjes et al., 2022; 2025; Yamashita et al., 2022). However, the magnitude and fate of these contributions remain poorly constrained.

This project combines laboratory experiments and field expeditions to study RDOM formation, transformation, and persistence. Planned cruises include one to Baffin Bay (expected 2026) and one to Knipovich Ridge (anticipated 2029). The first phase will establish analytical protocols and lab-based process studies; the second will apply these methods in situ. Key research questions are:

• What roles do petroleum seepage and hydrothermal ROS play in DOM cycling?
• How do reduced species (e.g., H₂S, Fe, Mn) affect RDOM formation?
• How do microbial communities adapt to ROS?
• What are microbial RDOM transformations at different temperatures?

This project offers the successful candidate the opportunity to develop interdisciplinary skills—from advanced molecular characterization of DOM, lab incubations to participation in research expeditions. The candidate will help address a key uncertainty in the global carbon cycle by quantifying deep-sea sources of RDOM.

Further Reading

• Brünjes, J., Seidel, M., Dittmar, T., Niggemann, J., & Schubotz, F. (2022). Natural Asphalt Seeps Are Potential Sources for Recalcitrant Oceanic Dissolved Organic Sulfur and Dissolved Black Carbon. Environmental Science & Technology, 56, 9092-9102. doi: 10.1021/acs.est.2c01123
• Brünjes, J., Schubotz, F., Teske, A., & Seidel, M. (2025). Molecular composition of dissolved organic matter from young organic-rich hydrothermal deep-sea sediments. Limnology and Oceanography. doi: 10.1002/lno.12812
• Dittmar, T., Lennartz, S. T., Buck-Wiese, H., Hansell, D. A., Santinelli, C., Vanni, C., Blasius, B., & Hehemann, J.-H. (2021). Enigmatic persistence of dissolved organic matter in the ocean. Nature Reviews Earth & Environment, 2, 570-583. doi: 10.1038/s43017-021-00183-7
• Goranov, A. I., Chen, H., Duan, J., Myneni, S. C. B., & Hatcher, P. G. (2024). Potentially Massive and Global Non-Pyrogenic Production of Condensed “Black” Carbon through Biomass Oxidation. Environmental Science & Technology, 58, 2750-2761.doi: 10.1021/acs.est.3c05448
• Shaw, T. J., Luther III, G. W., Rosas, R., Oldham, V. E., Coffey, N. R., Ferry, J. L., Dias, D. M., Yücel, M., & Thibault de Chanvalon, A. (2021). Fe-catalyzed sulfide oxidation in hydrothermal plumes is a source of reactive oxygen species to the ocean. Proceedings of the National Academy of Sciences, 118(40), e2026654118. 10.1073/pnas.2026654118
• Yamashita, Y., Nakane, M., Mori, Y., Nishioka, J., & Ogawa, H. (2022). Fate of dissolved black carbon in the deep Pacific Ocean. Nature Communications, 13, 307. doi: 10.1038/s41467-022-27954-0

Modalities

The doctoral project will be supervised by Michael Seidel (University of Oldenburg) and Charlotte Kleint (University of Bremen). Depending on the personal expertise of the doctoral candidate, it will be supervised within the working group “Marine Geochemistry” (Oldenburg) or the working group “Petrology of the Ocean Crust” (Bremen). The remuneration corresponds to pay group TV-L 13 with 75% of the weekly working hours. The positions is 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.

The project mentoring team also includes: Florence Schubotz (MARUM), Solveig Bühring (MARUM), and Gunter Wegener (MARUM).

Main Tasks

• Scientific research in the field of:
  Marine Biogeochemistry / Organic Geochemistry / Organic carbon preservation
  
  
• Analysis of:
  Molecular composition of dissolved organic matter with help of ultrahigh-resolution mass spectroscopy and high-field nuclear magnetic resonance spectroscopy, trace metal analysis
• 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 Environmental Sciences, Geochemistry, Geoecology, Analytical Chemistry, Biochemistry or related fields with a focus on organic geochemistry or analytical chemistry. Documented proficiency in written and spoken English are required.

Further questions?

Questions about the project can be addressed to Michael Seidel ([Bitte aktivieren Sie Javascript]) or Charlotte Kleint ([Bitte aktivieren Sie Javascript]).