Birthe is interested in how marine microbial life interacts with organic matter. During her PhD studies at GEOMAR (Kiel, Germany) she sampled bacteria and phytoplankton in the sea surface microlayer (SML) during cruises to the Peruvian upwelling region and the Mediterranean Sea. Due to its exposed location the SML can influence air sea exchange processes such as gas exchange and the formation of sea spray aerosols. She was interested in understanding how the microbial community in the SML can survive in this demanding habitat with high radiation intensities and varying salinity, and how they can influence air sea gas exchange by excreting and degrading organic matter. Therefore, she combined molecular techniques and analysis of organic matter composition focussing especially on gel-like particles such as the polysaccharide-rich Transparent Exopolymer Particles (TEP).