I work within the sea4soCiety project of the CDRmare research mission (cdrmare.de/en/sea4society/). The working title of my thesis is "Dissolved organic matter as a potential contributor to carbon sequestration in coastal vegetated ecosystems".
The work for my PhD thesis will be conducted in scope of the sea4soCiety project of the CDRmare Research Mission of the German Marine Research Alliance (DAM). sea4soCiety aims to develop innovative approaches for improving the potential of Coastal vegetated ecosystems (CVE) for carbon dioxide removal (CDR) in Germany and worldwide that are ecologically feasible, environmentally sustainable, and legally and ethically sound. The main goals of the thesis will be to determine the chemical diversity, origin, and recalcitrance of dissolved organic matter (DOM) from four CVE - macroalgae, seagrasses, saltmarshes, and mangroves. Vegetated ecosystems will be compared to their non-vegetated equivalents to assess the capacity of these ecosystems for “blue carbon” storage. Moreover, temperate habitats of the German North Sea and Baltic Sea will be compared to tropical ones in Columbia and Indonesia. The focus will be on dissolved organic compounds that form through abiotic processes in sediments. These processes allow incorporation of sulfur into organic matter (dissolved organic sulfur, DOS), which in turn hinders the decomposition of these compounds. Additionally, dissolved black carbon (DBC) will be investigated. As decomposition of these DOM classes is in range of thousands of years (refractory DOM, RDOM), they bear potential to be useful contributors to coastal carbon sequestration. Diversity and sources of RDOM will be assessed via molecular methods including Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS). Based on the molecular fingerprints of DOM from different coastal habitats, recalcitrance of selected compounds will be investigated during controlled mesocosm experiments.