Ice Nucleation Activity and Aeolian Dispersal Success in Airborne and Aquatic Microalgae

Abstract

Microalgae are common members of the atmospheric microbial assemblages. Diverse airborne microorganisms are known to produce ice nucleation active (INA) compounds, which catalyze cloud and rain formation, and thus alter cloud properties and their own deposition patterns. While the role of INA bacteria and fungi in atmospheric processes receives considerable attention, the numerical abundance and the capacity for ice nucleation in atmospheric microalgae are understudied. We isolated 81 strains of airborne microalgae from snow samples and determined their taxonomy by sequencing their ITS markers, 18S rRNA genes or 23S rRNA genes. We studied ice nucleation activity of airborne isolates, using droplet freezing assays, and their ability to withstand freezing. For comparison, we investigated 32 strains of microalgae from a culture collection, which were isolated from polar and temperate aqueous habitats. We show that ∼17% of airborne isolates, which belonged to taxa Trebouxiphyceae, Chlorophyceae and Stramenopiles, were INA. A large fraction of INA strains (over 40%) had ice nucleation activity at temperatures ≥-6°C. We found that 50% of aquatic microalgae were INA, but the majority were active at temperatures <-12°C. Most INA compounds produced by microalgae were proteinaceous and associated with the cells. While there were no deleterious effects of freezing on the viability of airborne microalgae, some of the aquatic strains were killed by freezing. In addition, the effect of desiccation was investigated for the aquatic strains and was found to constitute a limiting factor for their atmospheric dispersal. In conclusion, airborne microalgae possess adaptations to atmospheric dispersal, in contrast to microalgae isolated from aquatic habitats. We found that widespread taxa of both airborne and aquatic microalgae were INA at warm, sub-zero temperatures (>-15°C) and may thus participate in cloud and precipitation formation.

Bioaerosol field measurements: Challenges and perspectives in outdoor studies

“…To mention a few examples, diverse and often abundant organisms producing bio-INPs have been revealed in addition to the well-known group of Gram-negative INA bacteria (Morris, Georgakopoulos, and Sands 2004), including Gram-positive bacteria (Failor et al 2017), fungi (Fr€ ohlich-Nowoisky et al 2015O'Sullivan et al 2015;Pummer et al 2015;Huffman et al 2013;Morris et al 2013), microalgae (Tesson and Santl-Temkiv 2018), and pollen (Dreischmeier et al 2017;Augustin et al 2013;Pummer et al 2012;von Blohn et al 2005). It is also becoming clear that bio-INPs typically predominate over minerals, in terms of their numeric abundance, across a wider temperature range than previously assumed, often comprising the majority of INPs at higher temperatures and down to -23 C (Hartmann et al 2019;Suski et al 2018;McCluskey et al 2018;Petters and Wright 2015;Mason et al 2015) or even colder (Tobo et al 2014).…”

Macromolecular fungal ice nuclei in &lt;i&gt;Fusarium&lt;/i&gt;: effects of physical and chemical processing

“…Fusarium begoniae is a plant pathogen of Begonia found in Germany with a potential wider distribution (Nirenberg and O'Donnell, 1998). Fusarium concentricum is a plant pathogen, which is frequently found in Central America and isolated from bananas (Aoki et al, 2001;Leslie and Summerell, 2006), and F. langsethiae is a broadly distributed cereal pathogen (Torp and Nirenberg, 2004). Some strains of these newly identified IN-active species are known to produce mycotoxins, which can threaten the health of humans and animals (Fotso et al, 2012;Kokkonen et al, 2012;Wing et al, 1993a, b).…”

The global impact of bacterial processes on carbon mass

“…Also processes of biological mass production from CO2 exist (autotrophy) and include photosynthesis (photoautotrophs). However, 310 despite the fact that photosynthetic microorganisms were reported in the atmosphere (Tesson and Santl-Temkiv, 2018) there is neither a clear indication yet of photosynthetic activity in clouds, nor of other modes of autotrophy.…”