Biogeochemical cycling of selected potentially harmful (ultra-)trace metals (Tl, REE) in coastal environments

• Applicant: Dr. Corinna Mori
• Subject Area: Oceanography
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 506141804

The project focuses on the influence of organic matter (OM) cycling on the biogeochemical cycling of the (ultra-)trace metals thallium (Tl) and the group of rare earth elements (REE) in coastal environments. These metals are typically not considered to be affected by bio-associated processes. Recent studies, however, indicate their parallel cycling with and their accumulation in organic matter in highly productive coastal environments, highlighting their potential to become harmful for coastal ecosystems. To this point, however, little is known about how these metals relate to which fraction of the OM pool and what influence OM cycling has on their biogeochemical cycling and vice versa. Furthermore, it has not been clarified which processes are responsible for the spatial and temporal changes observed in the concentration patterns, particularly in the coastal ocean. Considering the toxic nature of these metals, the anthropogenic alteration of their coastal inventory, as well as their use as oceanic process tracers, knowledge of their biogeochemical cycling is essential. Central aspects, which are to be addressed within the framework of this project, are: (1) The fate of naturally and anthropogenically derived Tl and REE in coastal ocean compartments, and (2) The impact of OM cycling, with respect to the living and non-living fraction of the OM pool, on the Tl and REE concentration patterns and vice versa.These aspects will be investigated via a highly interdisciplinary multiparameter approach, combining laboratory- and field-based approaches of different ecological complexity and temporal resolution. Using a microcosm approach, in which a North Sea typical phytoplankton community and representative single species are incubated under ambient and elevated Tl and REE conditions, the species specific impact on Tl and REE behavior and vice versa the response of phytoplankton to anthropogenic stress will be determined. The influence of a phytoplankton bloom and associated biogeochemical processes on the metal concentration patterns in the intertidal coastal zone as well as potential key drivers will be determined based on the outcomes of a mesocosm approach. The seasonal and interannual variability of Tl and REE cycles in the coastal environment as well as the main drivers that are responsible for shifts in the respective metal patterns will be assessed via multiparameter time series data collected in the nearshore area of the German North Sea. This approach will further be used to verify the outcomes of the micro- and mesocosm approaches and to evaluate the extent to which they are transferable to a natural system.

• DFG Programme: Research Grants