Summer pollen flora in rural and urban central England dominated by nettle, ryegrass and other pollen missed by the national aerobiological network

Abstract

Abundance and diversity of airborne pollen are important to human health and biodiversity. The UK operational network collects airborne pollen from 8 flowering trees, grasses and three weeds using Hirst traps and microscopic identification from urban areas. Knowledge of total pollen diversity and differences between rural and urban zones is limited. We collect environmental DNA (eDNA) from air during summer and autumn over 3 years with mini cyclones from one urban and one rural site. Data are analysed using next generation sequencing and metabarcoding. We find the most common genus, Urtica (57%), is also identified by the national network. The grasses Lolium (10%), Agrostis (2%) and Holcus (1%) are in the national network grouped at family level, while Brassica (2%), Chenopodium (1%), Impatiens (2%), Plantago (4%) and Tilia (7%) are not part of the UK operational network. DNA from 138 genera was identified, where 2% of the sample could not be associated with specific genera. 40% of the sample was classified better using eDNA methods at the genus level, than by optical methods. We calculate Bray–Curtis dissimilarity for the rural and urban zones and find a systematic difference in biodiversity. Overall, this shows airborne DNA reveals more information than methods based on morphological differences. The results also suggest data from sites located in large urban areas will be less representative for less populated rural areas. This presents a dilemma in balancing a network and the associated costs delivering health relevant information to the most populated areas vs. a nation-wide approach.

Storms facilitate airborne DNA from leaf fragments outside the main tree pollen season

“…Many bioaerosols can be detected with DNA approaches, with examples covering pollen (e.g. Brennan et al, 2019), bacteria (Innocente et al, 2017) and fungal spores (Hanson et al 2022a(Hanson et al , 2022b. A recent review by Johnson et al (2023) discussed developments in botanical applications of airborne eDNA detection and highlighted the future potential for advancements in this area, such as monitoring species dispersal, population structures and conservation.…”

“…Many studies on bioaerosols focus on specific periods such as transport of bacteria during spring (Abd Aziz et al, 2018), flowering of trees and plants (Adams-Groom et al, 2020) or sporulation and spore release during agricultural production periods (Hanson et al 2022a(Hanson et al , 2022bSkjøth et al, 2012). A consequence is that the bioaerosol composition outside of flowering periods or agricultural productive periods remains relatively unexplored, although studies such as Aalismail et al (2021) and Johnson et al (2021) have demonstrated the potential to advance understanding of plant ecology through monitoring atmospheric plant DNA, with possible relevance of long distance transport and detection of plant fragments, respectively.…”