When do fungi release their spores?

Fungal spore emissions are an important contributor to biogenic aerosols, but we have yet to understand under what conditions fungi release their spores. Nina Löbs and co-authors developed a new technique to measure emissions from single organisms and tested this out at ATTO and with controlled lab experiments. They published their results in the Open Access Journal Atmospheric Measurement Techniques.

large tropical fungi
Fungi of the species Rigidoporus microporus, on which they studied fungal spore emissions. © Sebastian Brill / MPI-C

Aerosols play an important role in various atmospheric processes, and in particular in cloud formation. Therefore it is important to know how they are produced. In the middle of the Amazon rainforest, far away from any human pollutants, most aerosols are biogenic. Among the larger size fractions, fungal spores are dominating. But what are the favorable conditions for fungi to release their spores? That’s exactly what Nina Löbs and her co-authors wanted to find out!

To approach this complex question, they set up an exciting, new measurement technique that allows measuring fungal spore emissions of single organisms. So far, most bioaerosol measurement techniques only measured atmospheric concentrations of all aerosols in the atmosphere. This, however, does not allow distinguishing between different source organisms or communities. With their new set-up at hand, they went to ATTO. Here, they could measure the spore release in the forest near the site under natural conditions. In addition, they set up laboratory experiments. This allowed them to compare the field measurements with others conducted under controlled conditions. That is important, because in nature several environmental conditions, such as temperature and humidity, might change at the same time. In a controlled lab experiment, it is possible to change just one of these at a time and keep the other factor constant. For their study, they now just focused on one species to illustrate the measurement techniques and results.

For this species, they found that the fungi release their spores mainly under high air humidity conditions, in the range of 62% to 96%. This makes sense, because water condensation is essential for the release of fungal spores. Temperature and light seem to only play a minor role. Nevertheless, the field measurements showed a strong diurnal cycle – the fungi released most spores at nighttime.

This is study is a first important step to decipher the relevance of spore-producing organisms such as fungi for atmospheric aerosols and their effects on regional weather and climate. Based on that, they want to investigate a variety of different fungal species. And they also want to measure spore concentrations at different canopy height levels and during different seasons. Such further studies will help to complete the picture.

The study called “Aerosol measurement methods to quantify spore emissions from fungi and cryptogamic covers in the Amazon” was published Open Access by Löbs et al. (2020) in Atmos. Meas. Tech. ,13.