Life is in the air

Identifying bioaerosols in the Amazonian atmosphere

Biological particles suspended in the atmosphere, such as pollen and fungi spores, are hugely important. Many previous studies, including those from ATTO, have focused on their chemical and physical properties. For example, scientists want to understand the role of these particles in cloud formation and precipitation.

But airborne biological particles, called bioaerosols, also influence the dynamics of the biosphere underneath. Plants and fungi disperse pollen and spores, respectively, to ensure pollination and fruit formation and to establish new organisms. In many cases, getting those particles into the air is essential to ensure their survival. Yet, so far, little is known about the biological taxonomic identity of these bioaerosols.

In a new study, Sylvia Mota de Oliveira and her colleagues set out to close that knowledge gap. They used the ATTO site to collect air samples at 300 m above the forest. Then, they used DNA sequencing to analyze the biological components that were present and figure out what species of plant or fungi they belong to.

Their results show that airborne species composition is intrinsically related to the environment underneath, and included many of the genera identified previously by the co-author Cybelli Barbosa, based on morphological characters. Many of the bioaerosols they identified in the air belong to Amazonian species frequent in the area. In plants, their findings are biased towards species that heavily rely on wind pollination. Species that use different mechanisms of pollen release have lower chances of the pollen grains becoming airborne. Therefore, the species composition in the atmosphere is different from the biosphere.

In addition to those Amazonian species, the team was also able to identify taxa living outside of the Amazon. They are mostly species known to have good wind pollination strategies. While their origin remains unclear, it is safe to assume that wind transported those particles across long distances to the study site. This confirms that wind transport is an important process to disperse species across regions.

But the most striking new insight is the stark contrast between the species composition in the near-pristine Amazonian atmosphere compared to urban areas. At ATTO the scientists found surprisingly few allergenic fungi and plant pathogens. They were still present, but in balance with rest of the vegetation. However, scientists have found that those species are relatively much more abundant in urban settings, which can cause problems. This means that plant and fungi populations are much more in harmony in forests, making the air healthier.

Sylvia Mota de Oliveira et al. published the study “Life is in the air: An expedition into the Amazonian atmosphere” Open Access in the journal Frontiers in Ecology and Evolution. doi: 10.3389/fevo.2022.789791

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