Relevance of bacterial exudates for flocculation and carbon sequestration in freshwaters

• Applicant: Dr. Katrin Attermeyer
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Microbial Ecology and Applied Microbiology
• Term: from 2015 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 279976145

Inland water bodies process huge amounts of carbon (C) from autochthonous (inside the system) and allochthonous (terrestrial surrounding) sources. Thereby, the dissolved organic carbon (DOC) fraction accounts for the largest part. It can either be mineralized and excess amounts released to the atmosphere or buried in sediments. The ratio of mineralization and burial determines the role of the system as a C source or sink. Bacteria play an important role in the C turnover and are key to DOC processing. However, the release of DOC by bacteria and their contribution to particle aggregation (flocculation) of allochthonous DOC is not yet well known. In this project, I aim to (1) quantify and qualitatively describe the DOC released by bacteria, (2) demonstrate a direct link between extracellular polymeric substances produced by bacteria and allochthonous DOC flocculation and (3) determine the role of both processes in the lakes` C cycling with emphasis on their C burial potential. This project will therefore contribute to a better understanding of lakes as C sources or sinks.The objectives will be answered in laboratory experiments and a field survey. The description of the quantity and quality of bacterial exudates and the role of bacterial exudates for allochthonous DOC flocculation will be investigated in two separate laboratory experiments. In a field survey, both processes and the sedimentation and C burial potential will be determined under natural conditions. I will apply high resolution chemical characterization of the DOC pool and stable isotope analysis, in combination with biomarkers such as phospholipid fatty acids for the C flow.

• DFG Programme: Research Fellowships
• International Connection: Sweden
• Host: Professor Dr. Lars Tranvik