Suchergebnisse

The production and export of terrestrial DOM is intimately related to processes in soils and the critical zone, and society relies on the sustained functioning of these systems (Küsel et al., 2016). Understanding mechanisms of SOM turnover and DOM production are thus crucial for proper management of ecosystems. Advancements in analytical technology – namely in soft ionization techniques coupled to ultrahigh resolution Fourier transform mass spectrometers – have revolutionized our view of ubiquitous and ultra-complex organic mixtures and have made the analysis routine in biogeochemistry (Minor et al., 2014; Smith et al., 2018; Zark and Dittmar, 2018). Knowledge about terrestrial DOM remains scarce, compared to advances in the fields of aquatic and marine sciences. Although terrestrial DOM is now seen as a valuable indicator and integrator of fast ecosystem responses (Roth et al., 2015, 2014), our understanding of molecular ecosystem imprints and potential new source or process markers is still limited.

This dissertation presents modern approaches for the identification of molecular markers and marker patterns as indicators for natural processes that transform dissolved organic matter (DOM) in the Critical Zone. The attached manuscripts describe the transformation of plant-derived DOM in the litter layer, soils and aquifers. The results of these investigations show that the interdisciplinary integration of untargeted ultrahigh-resolution mass spectrometry data on DOM composition with hydrological, isotopic and microbial information can substantially improve our understanding of the functioning of the Critical Zone.

Microorganisms have the ability to control the biophysical properties of their membrane lipids to thrive in natural environments. Different microbial species possess different membrane lipid compositions, even the composition of a single species is not always constant, but depends on the habitat conditions. Microorganisms adjust their membrane lipid composition by modifying the types of glycerol backbone (chain length, saturation, and branching) and head groups. Therefore, signatures of membrane lipids in the environmental samples could be used as biomarkers reflecting the physicochemical conditions and the community structures. With the increasing knowledge of lipid structures and their properties, the interpretation of lipid-based biomarker in environmental samples would be more accurate. By using lipidomics, this thesis aimed at (i) identifying new lipid isomers to help improve the precision of its derived proxy, (ii) expanding the application of lipid biomarkers to the terrestrial subsurface critical zone for tracing the signal of surface down, (iii) providing a full lipid profile in the soils, investigating their sources and potential possibility as novel chemotaxonomic markers for bacteria.

This article is an outcome of the EuroMarine Foresight Workshop on "Chemical ecology of marine interactions: the chemical language that shapes future marine health", hosted by the University of Essex. Financial support for this event was provided by EuroMarine.-- 8 pages, 4 figures, 1 panel ; "Infochemicals" (information‐conveying chemicals) dominate much of the underwater communication in biological systems. They influence the movement and behavior of organisms, the ecological interactions between and across populations, and the trophic structure of marine food webs. However, relative to their terrestrial equivalents, the wider ecological and economic importance of marine infochemicals remains understudied and a concerted, cross‐disciplinary effort is needed to reveal the full potential of marine chemical ecology. We highlight current challenges with specific examples and suggest how research on the chemical ecology of marine organisms could provide opportunities for implementing new management solutions for future "blue growth" (the sustainable use of ocean resources) and maintaining healthy marine ecosystems ; M Saha acknowledges funding from the German Research Foundation (DFG) cluster of excellence "Future Ocean" for research grant CP1215, and the DFG under grant number SA 2571/2‐1. TW and GP acknowledge DFG for funding through CRC1127 ChemBioSys. EB received support from the CTM2014‐53818‐R (OstreoRisk) project funded by the Agencia Estatal de Investigación (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER), and by the project CoCliME an ERA4CS Network (ERA‐NET) initiated by JPI Climate, and funded by EPA (IE), ANR (FR), BMBF (DE), UEFISCDI (RO), RCN (NO), and FORMAS (SE), with co‐funding by the European Union (grant agreement number 690462) ; Peer Reviewed