Eva-Maria Meckel (PhD Student)

Research interests:

Hydrothermal influence to the ocean’s biogeochemistry

Hydrothermal circulation of organic and inorganic elements and their distribution in the rising, non-buoyant Plume

Research project:

Different roles of organic complexes for the transport of Cu and Fe in deep-sea and shallow hydrothermal vent fluids and plumes

Hydrothermal vent systems appear at the seafloor in geologically active areas such as mid-ocean ridges, volcanic arc systems, backarc basins and hotspot volcanoes. Their fluids withhold a unique chemistry created by fluid-rock interaction in the subsurface, which leads to a transport of dissolved metals and other compounds towards the seafloor. The actual metal- and chemical composition is controlled by many factors including host rock lithology, temperature-pressure conditions, fluid pathways in the subsurface, water-to-rock ratio, phase separation, phase segregation, and magmatic degassing. As the fluids discharge from the hydrothermal system due to cooling and mixing with cold seawater, metals dissolved in the fluids precipitate as sulfide minerals, or in increasingly oxygenated environment as sulfates and oxides and are partly released into the water column via the hydrothermal plume in both dissolved and particulate form. Not only are hydrothermal fluids enriched in many metals, but they have also distinct dissolved organic matter (DOM) composition from background seawater. DOM containing metal-binding functional groups such as hydroxide (-OH-), thiol (-SH-) or amino (NH2) groups are known to play an important role for metal solubility, transport and consequences for mineral precipitation.

While complex organic molecules cannot exist in hot (ca. >250°C) hydrothermal fluids, DOM molecules such as amino acids or proteins could still play an important role for forming stable complexes with hydrothermally derived metals in the early mixing plume or lower-temperature fluids. The presence of significantly elevated amino acid concentrations in hydrothermal fluids (even at rather high temperatures) implies that they are available as potential complexing agents for metals, possibly influencing their bioavailability and solubility. Wi­t­hin my PhD project, I want to study the molecular complexity of metal-organic ligands occurring in deep sea and shallow hydrothermal vent systems in collaboration with Prof. Thorsten Dittmar’s group at the ICBM of the University of Oldenburg, with a focus on trace metals such as iron (Fe) and copper (Cu). Before I started my PhD at the working group of Prof. Andrea Koschinsky, I have completed the master’s degree in “Marine Environemental Sciences” at the University of Oldenburg in the working group of Prof. Thorsten Dittmar. I have worked extensively with high pressure-temperature experimentation in my master thesis, where I investigated dissolved organic carbon transformation and cycling via radiocarbon measurements in hydrothermal environments simulating deep ocean hot spring conditions. The thesis is entitled “Hydrothermal transformation of dissolved organic matter – a radiocarbon and molecular study using AMS and FT-ICR-MS”.

During my PhD I’m not only comparing natural samples from vent systems of two upcoming cruises with a wide variety of parameters influencing the complexes, I also want to conduct autoclave experiments at the University of Bremen in the Working Group of Prof. Dr. Wolfgang Bach to investigate complexing or degradation influenced processes of metal-organic ligands by adjusting temperature, pressure and host-rock effects and their insights to the molecular composition of the complexing organics. The natural samples for the project originate from the cruises in 2023 to Atlantic mid-ocean ridge hydrothermal systems (M190) and shallow and deep-sea hydrothermal systems in the Mediterranean Sea close to Milos (M192).