Molecular composition of Southern Ocean dissolved organic matter and its relation to structure and activity of prevailing microbial communities

• Applicant: Dr. Jutta Niggemann
• Subject Area: Oceanography
• Term: from 2011 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 199760658

Marine dissolved organic matter (DOM) contains two orders of magnitude more carbon than all living biomass in the ocean combined. Despite its importance for global element cycles, our understanding of sources and sinks, composition and dynamics of the DOM pool is still limited. DOM is the main carbon and energy source for heterotrophic marine microorganisms. Emerging analytical techniques provide molecular information on DOM and microbial communities in unsurpassed detail. We hypothesize that DOM molecular composition and the microbial community are closely interrelated and that the microbial imprint in DOM can be traced through the major deep water masses back to its main origin in the microbially most active surface layers. The Southern Ocean is characterized by close proximity of different water masses. Spatial and temporal variability of primary productivity render the system highly dynamic with respect to DOM composition and microbial community structure. Novel analytical techniques will provide us with a most detailed molecular fingerprint on both, DOM and the microbial community. Based on DOM molecular fingerprints we will define DOM regimes in the ocean. We hypothesize that the driving force behind these regimes are microbial acitivity and community composition. On a comprehensive molecular level, we will relate microbial processes to the cycling of specific DOM compounds. This will be a first step towards a systems biology approach in biogeochemistry.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas - with renewal proposal 2025 - 2030
• Participating Person: Professor Dr. Thorsten Dittmar