The origin of maleimides in recent sediments - Sources, formation processes and palaeoenvironmental implications

• Applicant: Dr. Sebastian Näher, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 253132634

Chlorophylls and bacteriochlorophylls are the most abundant and most important pigments on Earth. These compounds and their transformation products (chlorins, porphyrins, metalloporphyrins and maleimides) can be preserved in recent limnic and marine sediments, sedimentary rocks and crude oils and serve as valuable palaeoenvironmental proxies. Among these, maleimides (1H-pyrrole-2,5-diones), the assumed oxidation products of tetrapyrroles (i.e. chlorophylls, bacteriochlorophylls, related derivatives, hemes, phycobilins) have so far hardly been studied in recent sediments, most studies being focused on ancient deposits. Their formation processes are still incompletely understood and precursors of many maleimides are not known. In this project, the characterisation of maleimides in aquatic systems with different biogeochemical history will expand the very limited knowledge of maleimide sources and formation pathways in recent aquatic environments, which represents an important step to accurately apply them as biomarkers. These markers might be used for instance to describe changes in productivity and carbon cycling, microbial community structure, water column properties (e.g. photic zone anoxia/euxinia (persistent versus periodic), chemocline depth) and depositional conditions during sedimentation and diagenesis. This project aims at identifying maleimide sources by analysis of their distributions and comparing these with tetrapyrroles obtained in the same samples. Existing analytical procedures to determine maleimides with apolar functional groups will be modified to include polar maleimides. It is, hence, the first attempt to analyse polar maleimides in recent sediments. Furthermore, stable carbon and nitrogen isotope signatures of maleimides will be measured in environmental samples. This approach will enhance the understanding of the metabolism and cycling of organic carbon and nitrogen and to reconstruct changes in productivity, nutrient cycling and food web relationships.

• DFG Programme: Research Fellowships
• International Connection: Australia
• Host: Professorin Kliti Grice