Aerobiological teaching from a mycological perspective

The atmosphere contains an incredible diversity of spores. To those looking at an air sample for the first time the diversity may appear overwhelming. However, learning the basic principles of aeromycology can provide some clarity to air samples. Among those principles are the methods of spore discharge, the influence of meteorological conditions, diurnal rhythms of spore discharge, and features of spore morphology. Spores are discharged either passively or through active mechanisms. Wind dispersal is the best understood passive method; however, many spores are also discharged by rain. Active mechanisms that propel spores into the atmosphere are common in fungi. Many ascospores and basidiospores are discharged by mechanisms that require moisture or high humidity. Because of the methods of discharge, meteorological factors have a great influence on atmospheric concentration. In fact, aerobiologists recognize a dry air spora and a wet weather air spora. The dry air spora is often dominated by Cladosporium, Alternaria, Curvularia, Pithomyces, Drechslera, smut spores and rust spores. The wet weather air spora is typically dominated by ascospores, although basidiospores will likewise increase after periods of rain. Diurnal rhythms are also attuned to the methods of discharge with passively dispersed members of the dry air spora common during the daytime when wind speeds are typically highest. Basidiospores and some ascospores are common during the late night and early morning hours when humidities are high. These principles help aerobiologists understand how and when spores are entrained into the atmosphere; however, knowledge of the microscopic features of spore morphology are necessary for spore identification. Spore shape, number of cells, wall thickness, surface ornamentation, attachment scars, and color are all important features for identification. Through the application of these principles, aerobiologists have begun to quantify the great diversity of spores present in the atmosphere, but there is still much to be learned.