"Multidimensional DOM fluorescence characterization utilizing an underway sample treatment optical sensor assembly"
Broader background of the proposed research project
Assessing the dynamics of the DOM pool and its interactions with the marine ecosystem re-quires rapid in situ sensing techniques that can complement sophisticated laboratory-based analytical methodologies like FT-ICR-MS. Namely these rapid sensing approaches target inherent optical properties including the absorption of chromophoric dissolved organic matter (CDOM) and the fluorescent fraction (FDOM) the latter typically analyzed by excitation-emission-matrix-spectroscopy (EEMS) (Moore et al. 2009; Zielinski et al. 2009). While EEMS are an established laboratory method and extensive field data is (e.g. Garaba et al. 2014) and will be available from seagoing expeditions, recent developments achieved in the EU project NeXOS (www.nexosproject.eu) make in situ quasi-EEMS sensing possible (Delory et al. 2014). Additionally combining these methodologies with a microfluidic sample treatment system (Gaßmann et al. 2015) will result in a highly specific FDOM sensor system setup that can be operated underway, that means continuously during the vessels movement, thus providing unchallenged high resolution optical (F)DOM characteristics that can be linked to the “ecology of molecules”.
Outline for the proposed PhD research project
In the proposed project, we will test the hypothesis that FDOM excitation-emission-matrices show a high variability and complexity that can be linked to ecosystem dynamics. To address this topic we will correlate multidimensional FDOM data collected and processed during the approved research cruises on RV Sonne in 2016 and 2017, as well as data obtained from supplemental studies, with the EcoMol observables, namely from microbial communities (WP8) the pelagic chemical diversity (WP4), molecular interactions (WPs 6 and 7) and the sea surface processes (WP15). Underway and in situ sensing of complex FDOM spectral characteristics will be achieved by excitation-emission-matrix spectroscopy (EEMS) a) from discrete water samples with available state-of-the-art laboratory instrumentation and b) from an online quasi-EEMS sensing (a novel technological innovation) that is optionally c) coupled with a microfluidic sample treatment system (WP5) exposing the sample to high UV-radiation and/or adsorbing processing. All three approaches will use statistical chemometric analysis and establish a database of the molecular FDOM complexity of the non-living environment and the diversity of interactions with organisms thus contributing to the overall EcoMol concept.