eDNA-based assessment of biodiversity in air samples collected on Ameland

Restoration of biological diversity in natural and agricultural ecosystems is strongly dependent on the ability of organisms to reach potential habitat, and the incidence of such dispersal events. Therefore here we unravel the so-called ‘aerobiome’ with recently developed metabarcoding techniques for a better knowledge of the aerial dispersal of organisms.

Although plant dispersal has been studied for centuries, for many species the length and size of the ‘tale’ of their dispersal kernel remains very difficult to estimate. This is especially the case for groups with tiny propagules, such as ferns, mosses and orchids (e.g. De Groot et al. 2012). For microbes, we are only now starting to understand their immense variation in dispersal potential and strategies, debunking the previous assumption that ‘everything is everywhere’ and species composition is determined by environmental filters.

Sampling the community of organisms present in the air can help to get a better view on the aerial dispersal of organisms. In 2016 we performed a pilot study, in which we placed two air samplers on the roof of the Lumen building at the WUR campus, and determined the composition of daily air samples for a period of 21 days, based on a set of DNA markers that together target the entire prokaryotic and eukaryotic diversity (De Groot et al. 2021).

This pilot successfully allowed us to test the methodology, yet interpretation of the results in relation to dispersal potential was to some extent hampered by the high presence of crop species from nearby agricultural fields and species that most likely originated from nearby gardens. Therefore, a next step was to sample the aerobiome above a very different habitat, and ideally one that is more natural and for which detailed plant inventory data are available. The uninhabited eastern part of the Wadden Sea island of Ameland was chosen as study site, given the large amount of studies conducted here by a research team over the last centuries (Slim 2018). An added benefit is the distance to the mainland, which means that any observed species which unlikely present on the island, must have been dispersed over large distance.