04 September 2014

Ice Nucleation and its Effect on the Atmospheric Transport of Fungal Spores


Fungal spores, the reproductive structures in the lifecycle of fungi, are abundant in the atmosphere. These spores can be transported large distances to high altitudes in the troposphere and even into the stratosphere by wind dissemination. Ice nucleation on fungal spores may be important because it could influence the frequency and properties of ice and mixed-phase clouds in the atmosphere. In addition, ice nucleation on fungal spores followed by precipitation may be an important spore removal mechanism in the atmosphere. For the first time, scientists, including a U.S. Department of Energy researcher at Pacific Northwest National Laboratory, measured the ice nucleation properties of 12 different species of fungal spores in the laboratory, and globally modeled the effect of ice nucleation in the atmosphere on the long-distance transport of spores. The team found that these spores, abundant in the atmosphere, caused water droplet freezing above homogeneous freezing temperatures. At temperatures below −20◦C, all of the fungal spores were less efficient ice nuclei compared to Asian mineral dust on a per surface area basis. Ice nucleation scavenging of these fungal spores in mixed-phase clouds can decrease the concentrations of fungal spores in near-surface air over the oceans and polar regions, and decrease concentrations in the upper troposphere. While the treatment of ice nucleation scavenging is simplified, this study gives an initial indication of the regions that are most sensitive to removal of spores due to scavenging by ice nucleation, as well as the potential magnitude of these effects.

D I Haga
University of British Columbia
Haga, DI, SM Burrows, R Iannone, MJ Wheeler, RH Mason, J Chen, EA Polischuk, U Pöschl, and AK Bertram.  2014.  "Ice nucleation by Fungal Spores from the Classes Agaricomycetes, Ustilagnimycetes, and Eurotiomycetes, and the Effect on the Atmospheric Transport of these Spores."  Atmospheric Chemistry and Physics 14: 8611-8630, doi:10.5194/acp-14-8611-2014.