Research topics: marine cycles of trace metals and silicon

Dr. Bianca Torres Liguori Pires and Dr. Corinna Mori are the two young ICBM researchers to receive 24 months funding from the programme budget of the Presidential Chair of the Oldenburg University. "By the university funding, two very promising young researchers are granted the time and opportunity required to apply for third party funding“, says Prof. Dr. Katharina Pahnke-May, who is heading the research group Marine Isotope Geochemistry at the ICBM, where Liguori an Mori found their temporary scientific home. “This kind of sponsorship provides a “jump start“ to young scientists shortly after having completed their doctorate and enables them to gather experience in acquiring third-party funding, project management and independent research to sharpen their professional profile,“ Pahnke-May adds.

Trace Metals and Organic Matter
Mori, who worked on selected trace metals in the Southern North Sea during her doctorate, is going to focus her future research on the linked cycling of organic matter and toxic trace and ultra trace metals in the coastal ocean. As the name implies already, trace metals normally occur at very low levels in the environment, ultra trace metals in even lower concentrations. “Coastal oceans, such as the southern North Sea, are not only characterized by a high organic matter load, but are also under the influence of anthropogenic element fluxes“, says Mori. The intensive organic matter recycling and potentially associated accumulation of (ultra-)trace metals in coastal areas might potentially lead to harmful trace metal levels for marine biota.

Mori will focus on the toxic (ultra-)trace metals thallium and the group of rare earth elements, two examples of which are gadolinium and neodymium. They are considered biologically inactive but have been suggested to cycle passively with organic matter especially under conditions of high primary production. Yet, details about the biogeochemical cycling of these trace metals are elusive. Given their toxic nature and the increasing anthropogenic pressure in coastal areas highlight the importance for a better understanding of their biogeochemical cycling. The central aspect of Mori‘s project thus will be to determine the influence organic matter cycling has on the concentration pattern of the (ultra-)trace metals in coastal environments. To address this aspect, she will use a highly interdisciplinary research approach, combining lab-, mesocosm and field-based multi-parameter approaches of different temporal and spatial resolution and different ecological complexity. For this she will rely on the versatile and modern analytical infrastructure provided at the ICBM, including the ‘marine chemical analytics’ (MCA) facilities.

Closing knowledge gaps around one of the most frequent chemical elements
Bianca Liguori will utilize silicon isotopes to fill an important gap in the understanding of the silica cycle in the oceans in her future project. In her doctoral thesis, she already investigated the changes in silicate utilisation and cycling in the central Arctic Ocean using silicon isotopes. – Isotopes of a chemical element have the same number of protons but different numbers of neutrons. They hence exhibit identical chemical properties but differ in relative atomic mass, which leads to a different preferential incorporation into biogenic matter.

“Dissolved silica is essential for diatoms to build their siliceous skeleton made of biogenic silica. It is therefore one of the most important macronutrients in the oceans”, says Liguori, and she continues, ”diatoms are the dominant primary producers in the oceans responsible for the production of the majority of organic carbon and oxygen, making them key players in the global carbon and silica cycles and global climate”. When diatoms die, part of the biogenic silica accumulates on the seafloor. “Yet, little is known about the factors controlling biogenic silica preservation in marine sediments,“ Liguori says. In order to better understand this silica sink and potential geochemical modifications occurring in sediments, she will analyze silicon isotopes and concentrations in porewater samples. Furthermore, she will compare two areas in the South Pacific that are marked by contrasting primary production conditions and assess how these conditions affect the biogenic silica preservation in the sediments.