Dissolved organic matter, Fe-binding ligands and metal bioaccumulations in Indian Ocean hydrothermal systems
Hydrothermal vents are one of the major sources of trace elements in the deep ocean as well as labile dissolved organic matter (DOM) which can be utilized by vent microorganism. This extreme environment harbors dense benthic communities which benefit from chemicals release from the vents. Hydrothermal fluids are generally enriched with trace metals, sulfide and other elements. Trace metals such as iron (Fe) and copper (Cu) are essential micronutrients for normal growth and development of living organisms but they can also be toxic to vent organisms. The bioavailability and toxicity of these metals depend not only on concentration but also on the form in which metals exist in the environment and how much they can be incorporated in organisms. Metal release from vents (such as Fe) will be largely oxidized and precipitate in oxide forms upon the mixing with oxygen-rich deep water. Microbial organisms living in the vents have the ability to produce metal-binding organic ligands which then contribute to stabilization of dissolved metal species resulting in increased mobility and bioavailability in the bigger scale in the open ocean. However, the knowledge of DOM in a holistic picture of hydrothermal pathways (from vent orifices to open ocean), the nature of organic iron-binding ligands in deep-sea hydrothermal systems and metal accumulations in vent animals are still scarce.
The aims of my study consist of three main parts:
- to understand molecular characteristics of hydrothermal dissolved organic matter as the results of abiotic and biotic synthesis within the hydrothermal systems (from the hydrothermal sources up to the mixing zones).
- to investigate the Fe-binding ligands in hydrothermal pathways by voltammetric ligand titration
- to study metal bioaccumulations in the tissues of hydrothermal organisms
This study will give us holistic pictures about how hydrothermal vents contribute to deep-ocean dissolved organic matter pool, how the organic binding ligands increase mobility and bioavailability of iron in hydrothermal pathways and how endemic vent animals cope with metal stress und uptake in natural conditions.
My study major sites are located in the German contract area for massive sulfides in the Indian Ocean (Federal Institute for Geosciences and Natural Resources BGR in Hanover, INDEX project) which are Kairei and recently discovered Pelagia hydrothermal vent fields. My research is part of the BGR contract focusing on the environmental study for the future deep-sea mining.
In January 2016, I participated in the INDEX 2016 expedition on board of N/O Pourquoi pas? (IFREMER, France) to the Indian Ocean and collected the hydrothermal fluid and plume samples. Later on, with the cooperation of ICBM (Prof. Thorsten Dittmar, University of Oldenburg), I had a great opportunity to analyze my hydrothermal samples for DOM using the FT-ICR-MS (Fourier-transform ion cyclotron resonance mass spectrometry). Organic ligand analysis and major element analyses were performed using voltammetric techniques and ICP-OES or ICP-MS in our laboratory at Jacobs University Bremen.
In addition to my main deep-sea hydrothermal research, I also participated in an Icelandic shallow hydrothermal vent project in cooperation with Dr. Solveig Bühring (Hydrothermal Geomicrobiology Group, MARUM). During this project I took hydrothermal fluids from HveravÍk bay in northwest Iceland for major elements and Fe binding ligands.
Paul, S. A. L.; Zitoun, R.; Noowong, A.; Manirajah, M. and Koschinsky A. (2021) Copper-binding ligands in deep-sea pore waters of the Pacific Ocean and potential impacts of polymetallic nodule mining on the copper cycle. Scientific reports 11: 18425. https://doi.org/10.1038/s41598-021-97813-3
Noowong, A., Gomez-Saez, G. V., Hansen, C., Schwarz-Schampera, U., Koschinsky, A. and Dittmar, T. (2021): Imprint of Kairei and Pelagia deep-sea hydrothermal systems (Indian Ocean) on marine dissolved organic matter. Organic Geochemistry 152, 104141. 10.1016/j.orggeochem.2020.104141
Gomez-Saez, G.V., Niggemann, J., Dittmar, T., Pohlabeln, A.M., Lang, S.Q., Noowong, A.,Pichler, T.,Wörmer, L. and Bühring, S.I. (2016): Molecular evidence for abiotic sulfurization of dissolved organic matter in marine shallow hydrothermal systems. Geochimca et Cosmochimica Acta 190, 35-52. 10.1016/j.gca.2016.06.027
Noowong, A.; Gomez-Saez, GV.; Hansen, CT.; Schwarz-Schampera, U.; Koschinsky, A. and Dittmar, T.: Molecular Characterization of DOM in Indian Ocean Hydrothermal Systems (Talk); Goldschmidt 2019, Barcelona, Spain , 18.08 -23.08.2019. (Oral Presentation). Abstract available at https://goldschmidt.info/2019/abstracts/abstractView?id=2019004563