Preprints
https://doi.org/10.5194/bg-2021-187
https://doi.org/10.5194/bg-2021-187

  09 Aug 2021

09 Aug 2021

Review status: a revised version of this preprint is currently under review for the journal BG.

Bioaerosols and atmospheric ice nuclei in a Mediterranean dryland: Community changes related to rainfall

Kai Tang1,, Beatriz Sánchez-Parra1,2,, Petya Yordanova1,, Jörn Wehking1,a, Anna Theresa Backes1, Daniel Andrew Pickersgill1, Stefanie Maier2, Jean Sciare3, Ulrich Pöschl1, Bettina Weber1,2, and Janine Fröhlich-Nowoisky1 Kai Tang et al.
  • 1Multiphase Chemistry Department, Max Planck Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany
  • 2Institute of Biology, University of Graz, Holteigasse 6, 8010 Graz, Austria
  • 3Climate and Atmosphere Research Center, The Cyprus Institute, 2121 Nicosia, Cyprus
  • anow at: HygCen Austria GmbH, Werksgelände 28 5500 Bischofshofen, Austria
  • These authors contributed equally to this work.

Abstract. Certain biological particles are highly efficient ice nuclei (IN), but the actual contribution of bioparticles to the pool of atmospheric IN and their relation to precipitation are not well characterized. We investigated the composition of bioaerosols, ice nucleation activity, and the effect of rainfall by metagenomic sequencing and freezing experiments of aerosol samples collected during the INUIT 2016 campaign in a rural dryland on the Eastern Mediterranean island Cyprus. Taxonomic analysis showed community changes related to rainfall. For the rain-affected samples, we found higher read proportions of fungi, in particular of Agaricomycetes, which are a class of fungi actively discharging their spores into the atmosphere in response to humidity changes. In contrast, the read proportions of bacteria were reduced, indicating an effective removal of bacteria by precipitation. Freezing experiments showed that the IN population in the investigated samples was influenced by both rainfall and dust events. For example, filtration and heat treatment of the samples collected during and immediately after rainfall yielded enhanced fractions of heat-sensitive IN in the size ranges larger than 5 μm and smaller than 0.1 μm, which were likely of biological origin (entire bioparticles and soluble macromolecular bio-IN). In contrast, samples collected in periods with dust events were dominated by heat-resistant IN active at lower temperatures, most likely mineral dust. The DNA analysis revealed low numbers of reads related to microorganisms that are known to be IN-active. This may reflect unknown sources of atmospheric bio-IN as well as the presence of cell-free IN macromolecules that do not contain DNA, in particular for sizes < 0.1 μm. The observed effects of rainfall on the composition of atmospheric bioaerosols and IN may influence the hydrological cycle (bioprecipitation cycle) as well as the health effects of air particulate matter (pathogens, allergens).

Kai Tang et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-187', Alexandr Safatov, 15 Sep 2021
    • AC1: 'Reply on RC1', Janine Froehlich, 14 Oct 2021
  • RC2: 'Comment on bg-2021-187', Anonymous Referee #2, 30 Sep 2021
    • AC2: 'Reply on RC2', Janine Froehlich, 14 Oct 2021

Kai Tang et al.

Kai Tang et al.

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Short summary
Metagenomic sequencing and freezing experiments of aerosol samples collected on Cyprus revealed rain-related short-term changes of bioaerosol and ice nuclei composition. Filtration experiments showed a rain-related enhancement of biological ice nuclei > 5 μm and < 0.1 μm. The observed effects of rainfall on the composition of atmospheric bioaerosols and ice nuclei may influence the hydrological cycle as well as the health effects of air particulate matter (pathogens, allergens).
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