One year of temporal characterization of fungal spore concentration in São Paulo metropolitan area, Brazil

Abstract

There are very few studies related to the characterization of biological components, especially fungal ones, present in the particulate matter (PM) of atmospheric aerosols in Brazil. The biogenic components of PM can have a direct relationship with respiratory diseases outbreaks and can also be linked to climate processes. Studies indicate that fungal spores constitute one of the major biological components present in the atmosphere and can be responsible for a significant amount of particulate mass concentration. This work aims to (i) identify the main fungal types in the atmosphere of São Paulo; (ii) estimate the fungal type concentrations and variations in the atmosphere; (iii) investigate the fungal spore seasonality; and (iv)estimate their diurnal behavior. In order to achieve that, a "Burkard 7-day Recording" air sampler operating at 10L/min was used to collect spore samples on a 24/7 basis, from September 2013 to September 2014, at the main campus of the University of São Paulo, an area mostly impacted by vehicular emission and characterized by the presence of green areas. Fungal types were grouped considering their morphological similarity (i.e., cell number, coloration, shape and size) and predetermined taxonomic group (phylum, family and genus). After this initial classification, fungal types were grouped in three main groups, Ascomycota and Basidiomycota, which included only the teleomorph form of the fungi, and Deuteromycota, which includes the anamorph form of both phyla. Fungal types were characterized using an optical microscope, and 45 major fungal types were found, with Basidiomycota being the main phylum. The average concentration was 5736 (± 2459) spores/m³ per day, with the highest concentration at 23780 spores/m³ in autumn at night and the lowest concentration at 567 spores/m³ in autumn in the morning. Higher concentrations of Ascospores (AS) and Basidiospores (BS) occurred in spring and summer, whereas Mitospores presented the highest concentration in winter and autumn. In addition, spore concentrations presented different profiles according to hourly variation, with the highest concentration of Total spores occurring at dawn. However, the concentration of Mitospores was higher during the afternoon, probably due to spore releasing mechanisms or to their transport. Ascomycota and Deuteromycota presented an antagonistic behavior in most situations.