Jasmin Sabrina Seifried

• Airborne bacteria are omnipresent in the atmosphere, having a substantial impact on ecological patterns (distribution of organisms), medical concerns (spreading of pathogens) and climate functioning (condensation nuclei). Despite its unquestionable importance for ecosystem functioning, airborne bacteria, and particularly those in marine bioaerosols, are still understudied. The absence of standardised methods further complicates proper comparabilty of the few bioaerosol studies that exist to date. The current thesis aimed to gather basic knowledge about abundances and composition of bacterial communities in marine bioaerosols and how their spatial and seasonal dynamics may be affected by environmental factors. The spatial dynamics were studied in samples which were taken during a cruise with the research vessel Heincke from the North to Baltic Sea, whereas seasonal dynamics were investigated in a yearlong sampling campaign at the remote island of Helgoland (German Bight, North Sea). Furthermore, a complementing evaluation of quantification methods was performed to identify suitable procedures that could potentially be used for standardised investigations. All analyses were carried out using culture-independent methods (pyrosequencing, ARISA, q-PCR) in order to avoid any possible biases. All things considered, the current findings elucidated highly diverse bacterial communities in marine bioaerosols which were subject to strong temporal and spatial fluctuations. The observed patterns further supported the idea of an airborne bacterial core cumminty. The evaluation of modern methodologies to assess this diversity clearly underlined the urgent need for further investigations. Therefore, the current findings represent an important step towards a better understanding of patterns and processes within airborne bacterial communities, thereby advancing our knowledge on bioaerosols and their driving factors.