Ice nucleation by fungal spores from the classes <i>Agaricomycetes</i>, <i>Ustilaginomycetes</i>, and <i>Eurotiomycetes</i>, and the effect on the atmospheric transport of these spores

Abstract

Abstract. We studied the ice nucleation properties of 12 different species of fungal spores chosen from three classes: Agaricomycetes, Ustilaginomycetes, and Eurotiomycetes. Agaricomycetes include many types of mushroom species and are widely distributed over the globe. Ustilaginomycetes are agricultural pathogens and have caused widespread damage to crops. Eurotiomycetes are found on all types of decaying material and include important human allergens. We focused on these classes because they are thought to be abundant in the atmosphere and because there is very little information on the ice nucleation ability of these classes of spores in the literature. All of the fungal spores investigated contained some fraction of spores that serve as ice nuclei at temperatures warmer than homogeneous freezing. The cumulative number of ice nuclei per spore was 0.001 at temperatures between −19 °C and −29 °C, 0.01 between −25.5 °C and −31 °C, and 0.1 between −26 °C and −31.5 °C. On average, the order of ice nucleating ability for these spores is Ustilaginomycetes > Agaricomycetes ≃ Eurotiomycetes. The freezing data also suggests that, at temperatures ranging from −20 °C to −25 °C, all of the fungal spores studied here are less efficient ice nuclei compared to Asian mineral dust on a per surface area basis. We used our new freezing results together with data in the literature to compare the freezing temperatures of spores from the phyla Basidiomycota and Ascomycota, which together make up 98% of known fungal species found on Earth. The data show that within both phyla (Ascomycota and Basidiomycota), there is a wide range of freezing properties, and also that the variation within a phylum is greater than the variation between the average freezing properties of the phyla. Using a global chemistry–climate transport model, we investigated whether ice nucleation on the studied spores, followed by precipitation, can influence the transport and global distributions of these spores in the atmosphere. Simulations suggest that inclusion of ice nucleation scavenging of these fungal spores in mixed-phase clouds can decrease the annual mean concentrations of fungal spores in near-surface air over the oceans and polar regions, and decrease annual mean concentrations in the upper troposphere.

Review: The Use of Real-Time Fluorescence Instrumentation to Monitor Ambient Primary Biological Aerosol Particles (PBAP)

“…They can do this by directly scattering light, but also by acting as "seeds" for the growth of ice nuclei (IN) in cloud formation [12]. Ice nucleating particles (INPs) are generally thought to represent a small subsection of total ambient particles.…”

Characterization of free amino acids, bacteria and fungi in size-segregated atmospheric aerosols in boreal forest: seasonal patterns, abundances and size distributions

“…S7). There is some evidence that cloud-active particles larger than ∼ 1 µm are biological in origin (Haga et al, 2014;Hassett et al, 2015;Mason et al, 2016;Möhler et al, 2007), and in mixedphase cloud conditions, PBAPs may play an important role in triggering rainfall. Collectively, the different correlations observed between rainfall and PBAP components suggest that a potential feedback mechanism may persist at the boreal forest.…”

The micro-orifice uniform deposit impactor–droplet freezing technique (MOUDI-DFT) for measuring concentrations of ice nucleating particles as a function of size: improvements and initial validation

“…The DFT used here has been employed previously to study immersion freezing by biological particles and mineral dust ( Chernoff and Bertram, 2010;Wheeler and Bertram, 2012;Haga et al, 2013Haga et al, , 2014Wheeler et al, 2015). The technique is based in part on the earlier design of Koop et al (2000).…”

“…The ice nucleating properties of collected particles are then determined in the laboratory by a microscope-based droplet freezing technique (the DFT) that is capable of measuring the concentrations of INPs in the immersion mode to a temperature of approximately −37 • C (Koop et al, 1998;Chernoff and Bertram, 2010;Haga et al, 2013Haga et al, , 2014Wheeler et al, 2015), which is roughly the homogeneous freezing temperature of water droplets 100 µm in diameter (Pruppacher and Klett, 1997). The MOUDI-DFT permits measurements at a higher size resolution and over a wider range of temperatures than most of the size-resolved instrumentation discussed above.…”