Seasonal Dynamics of the Compositions and Concentrations of Microbiomes in the Atmospheric Environment at a Subtropical Location

Understanding the types of microbes present and their concentrations over time is essential for deciphering the physical, chemical, and biological processes in the atmospheric environment. In this study, Hong Kong, which experiences four distinct seasons, was selected as the study site. High-throughput amplicon sequencing of the 16S rRNA gene was utilized to analyze the microbiomes present, while a light/laser-induced fluorescence (LIF) instrument was employed to characterize the real-time concentrations of fluorescent aerosol particles (FAPs) or bioaerosols. Seasonal variations in the microbiomes were observed, primarily driven by less abundant taxa that were unique to specific locations. Conversely, spatial variations were minimal, suggesting a homogeneity of microbiomes within the scale of a city. The major taxa of the microbiomes reflected the local environments (e.g., aquatic and soil), with neutral assembly processes dominating each season, indicating a minor role of selection in microbial assembly in the air. FAP concentrations were highest in the fall and winter seasons, deviating from measurements in temperate and tropical regions. Bioaerosol concentrations exhibited diurnal patterns, with higher concentrations during the daytime and lower concentrations at nighttime. Certain atmospheric pollutants were associated with bioaerosol concentrations, and positive matrix factorization analysis identified anthropogenic sources as key drivers of bioaerosol concentrations. In summary, the application of molecular techniques and LIF-based instrumentation has provided insights into the microbial composition of the atmospheric environment in a subtropical location, facilitating further investigations into the interactions involving these biological components.