FOR 5267:  Biogeochemical processes and Air-sea exchange in the Sea-Surface microlayer (BASS)

• Subject Area: Geosciences
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451574234

The sea-surface microlayer (SML) is the boundary layer between the atmosphere and the ocean and extends over the uppermost ~1 mm of the ocean. The SML is enriched with organic material and microbial cells and forms a distinct organic film between the ocean and the atmosphere. The existence of the SML is a global phenomenon, and due to its unique position, all material and energy exchange between the ocean and the atmosphere must occur through this boundary layer. A consensus in the literature describes the SML as a biofilm-like habitat. These facts place the SML in a central role in ocean and climate science. But our knowledge of the processes in the SML remains limited, as quantification of the interdisciplinary processes on the required spatial scales is difficult to achieve. The dynamic interaction of the SML with both the atmosphere and the ocean is largely unknown and currently does not allow for an assessment of the extent to which the SML affects biogeochemical cycling in the upper ocean and chemical-physical processes in the lower atmosphere. Our overall goal is to explore the importance of the SML as a bio- and photochemical reactor and how its reactivity affects ocean-atmosphere interactions. BASS will provide new insights into the accumulation of organic matter in the SML and how well-adapted microbes and (photo)chemistry transform organic matter. BASS will investigate to what extent photochemical production of trace gases and the presence of natural surfactants in the SML influence exchange processes between ocean and atmosphere. BASS will also investigate the coupling between the SML and bulk water, as this coupling determines the distribution of the unique products of bio- and photochemical processes in the SML into the upper ocean. Eight subprojects will collaborate in joint field campaigns in the open North Sea, a joint mesocosm study at the Sea-Surface Facility (University Oldenburg), and a joint experiment at the Wind Tunnel Hamburg (University Hamburg). BASS will combine interdisciplinary expertise, advanced technologies for observations at the millimeter scale or below, core infrastructures for controlled experiments, and state-of-the-art analytical facilities at the molecular and cellular level. Within this framework, BASS will advance observations of the SML to unprecedented spatial and temporal scales and provide a mechanistic description of the biogeochemistry of the SML and its impact on exchange processes, including physical models.

• DFG Programme: Research Units
• International Connection: Austria

Projects

• Bio-optical properties as real-time tracers of organic matter transformation in the SML (SP 1.3) (Applicants Röttgers, Rüdiger ;  Zielinski, Oliver )
• Biogeochemical processes and Air-sea exchange in the Sea-Surface microlayer (BASS): Chemical and photochemical transformation of organic matter (Applicants Friedrichs, Gernot ;  Hartke, Bernd ;  Herrmann, Hartmut )
• Coordination Funds (Applicant Wurl, Ph.D., Oliver )
• Diversity, metabolic activity and adaptation of bacteria in the sea-surface microlayer (Applicant Brinkhoff, Thorsten )
• Momentum and energy fluxes in the presence of surfactants (Applicants Buckley, Ph.D., Marc ;  Gade, Martin )
• SP1.1 Dynamic enrichment processes of organic matter in the SML (Applicants Engel, Anja ;  Schartau, Markus )
• SP 1.5 Molecular characterization of dissolved organic matter in the sea surface microlayer (SML) and its influence on the inorganic carbon cycle (Applicants Ribas Ribas, Ph.D., Mariana ;  Waska, Hannelore )
• SP 2.3 - Dynamics of convection linking the sea-surface microlayer (SML) with the bulk phase (Applicants Badewien, Thomas ;  Blasius, Bernd ;  Wurl, Ph.D., Oliver )
• The influence of the SML on trace gas biogeochemistry and air–sea gas exchange (Applicants Bange, Hermann W. ;  Marandino, Christa )

• Spokesperson: Professor Oliver Wurl, Ph.D.