Logo Universitat Bremen
Die Inhalte dieser Seite sind leider nicht auf Deutsch verfügbar.

Ann Noowong

Institution:Jacobs University Bremen
Room:JUB, Research III, room 102
Phone:+49 421 200 - 3228
E-mail:[Bitte aktivieren Sie Javascript]
Other webpage(s):Ann's Jacobs Uni web page
Ann Noowong

PhD project:

Geo-bio interactions in shallow and deep-sea hydrothermal ventsand metal-binding organic molecules produced by microbes in thevent fluids

Although hydrothermal vents are known as one of the most extreme habitats on earth, paradoxically there are highly productive and thriving ecosystems to be found here. Extremophile organisms found in vent environments are robust and able to handle extremities such as high temperatures, reduced gases and elevated metal concentrations. Life in vent surroundings is highly dependent on the organic substances produced by vent microbes. These microbes play a major role in vent benthic food chains, as they provide food sources to other vent dwellers.

Hydrothermal fluid released from vents is one of the major sources of metal input in the global ocean. Iron (Fe) and copper (Cu) concentrations observed in vent fluids are very high compared to the surrounding seawater. Even though Fe and Cu are essential micronutrients to marine life, Cu can be toxic when exceeding threshold concentrations. However, their bioavailability or toxicity are not determined by their total concentrations, but by their chemical speciation that can be assimilated by marine organisms.

There are reports showing that not only high amounts of strong organic metal-binding ligands are found in vent fluids, but also that these ligands are actively produced by vent microbes. The production of these ligands is a feedback mechanism to enhanced metal concentrations and thus preventing metal micronutrient depletion and also reducing its toxicity. Additionally, the presence of these strong metal binding-ligands in hydrothermal vents is facilitating the increase of dissolved metal inputs in vent systems. This new knowledge has lead recently to a re-estimation of Fe and Cu fluxes from hydrothermal vents into the ocean.
Nevertheless, the knowledge of how these vent microbes react to enhanced Fe and Cu concentrations in shallow and deep-sea vents is still scarce, as well as what kinds of organic metal-binding ligands they produced are still barely known. This study is set up in order to address the aforementioned lack of knowledge and understanding.

Firstly, seawater, sediment and vent fluids will be sampled from various shallow and deep-sea vent sites i.e. shallow vents in Hveravik Bay (Northern Iceland), Santorini shallow vents (Greece), Kueishantao Island shallow vent (Taiwan), Kermardec Arc intermediate/deep-sea vents (New Zealand) and the very hot deep-sea vents Karei and Edmond in the Indian Ocean. All these samples will be analyzed in order to acquire spatial overviews of metals, Fe, Cu and ligand concentrations in hydrothermal fluids and rising and dispersing plumes. This study will specifically focus on Fe, Cu, and their metal-binding ligand distributions in all study sites.
Secondly, two selected vent fluids (one shallow and one deep-sea) will be collected for natural vent microbial cultures. Manipulated incubation experiments will be carried out under varied Fe and Cu concentrations in order to investigate ligand production affected by Fe and Cu enhancements. Incubation samples will be taken at the beginning and at the end of experiments and will be analyzed for ligand concentrations. Likewise, ligand structures will also be determined after the incubations are completed.

This study will lead to a clearer image of bio-geochemical interactions of microorganisms and metal inputs (Fe and Cu) in shallow and deep-sea vent systems. Additionally, it will get a better understanding of Fe- and Cu-fluxes in vent environments and their role for biogeochemical processes in the ocean.

Thesis committee:

Prof. Dr. Andrea Koschinsky-FritscheJacobs University Bremen
Prof. Dr. Michael BauJacobs University Bremen
Prof. Dr. Thorsten DittmarUniversity of Oldenburg
Assoc. Prof. Dr. Sylvia SanderUniversity of Otago, Dunedin, New Zealand
Jun. Prof. Dr. Mirjam PernerUniversity of Hamburg