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

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