A quantitative investigation of airborne algae and lichen soredia obtained from pollen traps in south-west Spain

Over the course of nearly a year, counts were made of the algae present in the samples from a Burkard-type volumetric aerobiological trap which sampled continuously the atmosphere of the city of Badajoz (SW Spain), yielding hourly and daily results. The method permits only the major taxa of algae to be distinguished. Most of the algae found belong to the Chlorococcales (Chlorophyceae) and small centric diatoms (most of them Cyclotella). Some filamentous algae were also found and even Pediastrum coenobia as well as lichen soredia. Up to 12 Chlorococcales coenobia per cubic metre were found. The mean number of cells in the coenobia was more than 10, although some coenobia with more than 100 cells were observed. Their greatest concentration was during the months of May and June. The mean daily concentration of diatoms was highly variable, with maximal concentrations of more than 70 cells m[minus sign]3 in June. The maximum daily concentration of lichen soredia was 5 m[minus sign]3, with the concentration being fairly constant throughout the year but particularly high in spring and early summer. The hourly distribution showed maxima during the day and minima during the night. Significant positive correlations were found with temperature, and negative correlations with relative humidity in the three groups studied. The wind speed seemed to have a positive influence on the concentration of diatoms and Chlorococcales coenobia, although the direction of the wind also had an effect.