Project Details
Projekt
Organic matter: Abiotic transformations and microbial interactions
Subject Area
Oceanography
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 431491505
DynaDeep Phase 2 will address new research questions that emerged during Phase 1 at our core field site, Spiekeroog (southern North Sea, Germany), to unravel the functionality of deep subterranean estuaries (STE) beneath high-energy beaches and their relevance for land-ocean connectivity. To achieve this, seven subprojects will collaborate through joint field campaigns, experimental work, and mathematical modelling in an integrative framework. Subproject P3 will assess the relative importance of organic matter (OM) sources and elucidate abiotic and biotic transformations influenced by morphodynamics and site-specific conditions in the STEs of Spiekeroog and selected validation sites. We will focus on the supply of ancient (millennial) versus recent OM, and evaluate the role of high-energy beach STEs as organic carbon sinks of global relevance. We will challenge the concept of a carbon-limited bioreactor, addressing the paradox of low transformation rates, despite the apparent abundance of organic carbon substrates. Our research will be guided by the overarching hypothesis that the apparent stability of STE-OM is partly an intrinsic property of OM, but also emerges from STE-specific environmental processes. Furthermore, we hypothesize that the processes causing intrinsic and emergent OM stability are universal and can be generalized to other high-energy beach systems. Key areas of our research will be adsorption and desorption of OM to and from minerals, abiotic molecular reactions with reactive oxygen and reduced sulfur species, and the turnover of OM by free-living and sediment-attached microorganisms. To achieve these goals, we will conduct regular and event-specific field campaigns at Spiekeroog and at the two validation sites, Truc Vert (France) and De Panne (Belgium). We will perform laboratory experiments addressing the mobilization and molecular transformation of dissolved OM (DOM) from organic deposits in the STE, including processes such as iron reduction, Fenton reactions, and the microbial turnover of different DOM sources. We will use state-of-the-art ultrahigh-resolution mass spectrometry and high-field two-dimensional nuclear magnetic resonance spectroscopy to identify characteristic molecular patterns associated with these processes, contributing to an advanced mechanistic biogeochemical understanding of high-energy beach STE dynamics. Our subproject will provide essential data and process understanding on OM transformation rates and inventories, complementing insights from inorganic and microbiological studies, and informing reactive transport and global flux models.
DFG Programme
Research Units
International Connection
USA
Cooperation Partner
Professor Dr. Timothy J. Shaw
