Aerobiology in alpine environments: exploring pollen biodiversity and its impacts on human health

This review summarizes methods and relevant outcomes of aerobiological studies carried out in the alpine biome worldwide impacting the knowledge on the occurrence of airborne pollen and their origin, for biodiversity studies, models of transport, forecasts, and climate change scenarios, for the reconstruction of past vegetation, and the potential impacts on human health. Deposition sampling is the method of choice, while volumetric sampling is mostly performed in densely populated mountain ranges. Conventional microscopic identification of pollen of alpine environments is rarely complemented or replaced by molecular methods. The pollen bioaerosol mirrors the surrounding vegetation but includes components from medium and distant source locations. However, there is no uniform understanding on the definition of source-scales – crucial for the interpretation of the bioaerosol constituents – to which we propose an answer. Alpine habitats, with their cold-adapted plant communities, may react to increasing temperatures with shifts in their range. The potential of using pollen as a proxy to monitor such changes in alpine biomes has been exploited in paleoecology but rarely in aerobiology. Health impacts are linked to the low allergen load in the bioaerosol and the overall effect of the alpine climate in a highly natural environment. Generally, the soothing effect is reported for respiratory allergy patients, which may be jeopardized by seasonality and allergens transported from outside. The complex topography of mountain ranges does not allow for general assumptions on the quality and quantity of bioaerosol in alpine environments. We emphasize the importance of monitoring the bioaerosol in alpine environments to evaluate the effects of global change, and to optimize the management of respiratory health issue

Improvement in the Accuracy of Back Trajectories Using WRF to Identify Pollen Sources in Southern Iberian Peninsula

Airborne pollen transport at micro-, meso-gamma and meso-beta scales must be studied by atmospheric models, having special relevance in complex terrain. In these cases, the accuracy of these models is mainly determined by the spatial resolution of the underlying meteorological dataset. This work examines how meteorological datasets determine the results obtained from atmospheric transport models used to describe pollen transport in the atmosphere. We investigate the effect of the spatial resolution when computing backward trajectories with the HYSPLIT model. We have used meteorological datasets from the WRF model with 27, 9 and 3 km resolutions and from the GDAS files with 1 ° resolution. This work allows characterizing atmospheric transport of Olea pollen in a region with complex flows. The results show that the complex terrain affects the trajectories and this effect varies with the different meteorological datasets. Overall, the change from GDAS to WRF-ARW inputs improves the analyses with the HYSPLIT model, thereby increasing the understanding the pollen episode. The results indicate that a spatial resolution of at least 9 km is needed to simulate atmospheric flows that are considerable affected by the relief of the landscape. The results suggest that the appropriate meteorological files should be considered when atmospheric models are used to characterize the atmospheric transport of pollen on micro-, meso-gamma and meso-beta scales. Furthermore, at these scales, the results are believed to be generally applicable for related areas such as the description of atmospheric transport of radionuclides or in the definition of nuclear-radioactivity emergency preparedness

Mesoscale Atmospheric Transport of Ragweed Pollen Allergens from Infected to Uninfected Areas

Allergenic ragweed (Ambrosia spp.) pollen grains, after being released from anthers, can be dispersed by air masses far from their source. However, the action of air temperature,humidity and solar radiation on pollen grains in the atmosphere could impact on the ability of long distance transported (LDT) pollen to maintain allergenic potency. Here, we report that the major allergen of Ambrosia artemisiifolia pollen (Amb a 1) collected in ambient air during episodes of LDT still have immunoreactive properties. The amount of Amb a 1 found in LDT ragweed pollen grains was not constant and varied between episodes. In addition to allergens in pollen sized particles, we detected reactive Amb a 1 in subpollen sized respirable particles. These findings suggest that ragweed pollen grains have the potential to cause allergic reactions, not only in the heavily infested areas but, due to LDT episodes, also in the regions unaffected by ragweed populations

Plant-related biodiversity in the Alpine air: a review

Aerobiology can provide answers on the impacts of global change on plant biodiversity. It has been recognized that alpine environments are susceptible to such changes. However, there are only a few studies worldwide addressing plant-related particle biodiversity in air samples in open areas at high elevations or high geographical latitudes. This study reviews aerobiological papers that focus on assessing plant biodiversity in environments that are either part of the alpine biome or are functionally connected to it. PubMed was searched for “pollen and alpine”; morphological studies, taxonomical studies, honey studies, fossil pollen studies, and non-English studies were excluded from the resulting papers. Further relevant studies were retrieved from bibliographic references of the same articles and from Google Scholar. Based on 48 articles reviewed, i) the air sampling; ii) the identification method; iii) the bioaerosol biodiversity in relation to alpine vegetation were analyzed. As for i), deposition sampling is the method of choice to collect the alpine bioaerosol, while only a few studies use volumetric air samplers. As for ii), the current state of the art for the identification of pollen and non-pollen palynomorphs is microscopic analysis. Yet, results from DNA metabarcoding show a higher taxonomic resolution in identifying plant taxa, than microscopic analysis alone can achieve. As for iii), the establishment of relationships between bioaerosol and plant biodiversity implies the assessment of vegetation diversity and abundance at different scales from the receptor site. Back trajectory models are employed to trace the origin of extra local, long-distance sources. On the whole, the alpine bioaerosol mirrors the vegetation of wind-pollinated taxa from the immediate receptor site, e.g. herbaceous such as Poaceae, Cyperaceae, Juncaceae, and ferns. Entomophilous taxa, in contrast, are underrepresented. The biodiversity from the alpine air, however, does not only originate from local sources but also from extra-local, regional, and often over-regional areas. For the Eurosiberian plant region, the articles reviewed consistently report pollen from woody plants (Pinus, Picea, Corylus, Betula) above the timberline. Microscale air currents (0 - 2 km) cause the influx from around and below the timberline into the alpine air at the receptor site. Besides, mesoscale air masses (2 - 200 km) including topography-driven convections, thunderstorms, nighttime depositions as well as long-distance transport events (200 - 2000 km) add taxa to the bioaerosol. Knowledge on the composition of the plant bioaerosol in alpine environments facilitates the reconstruction of past climate, models of climate change scenarios, the interpretation of gene flow, and the genetic makeup of populations. Such is a valuable tool for plant conservation management in alpine environments. The authors acknowledge the support of NBFC to Fondazione Edmund Mach, funded by the Italian Ministry of University and Research, PNRR, Missione 4 Componente 2, “Dalla ricerca all’impresa”, Investimento 1.4, Project CN0000003

Endemic species in the aerobiome? Evidence from floristic and aerobiological studies in the Italian Alps

Pollen as a proxy for plant diversity helps to interpret vegetation and/or to model vegetation shifts under climate change scenarios. Within the BIOALPEC project "Biodiversity in Alpine Ecosystems," we investigate the qualitative-quantitative input of pollen and spores on the bioaerosol of high altitudes exploring implications for ecosystem functioning and biodiversity. Here we present how the local flora and surrounding vegetation are sources of the bioaerosol at alpine receptor sites in Trentino, Italy. The methodology applied involves floristic studies and bioaerosol sampling with passive gravitational traps. We surveyed the flora at different local scales, starting from the aerobiological sampler: i) within a circle of 10 m radius; ii) in 5 randomized 2 x 2 m plots within a circle of 100 m radius; iii) along a transect of 1000 m x 2 m