# Diversity and Seasonal Dynamics of Airborne Fungi in Nerja Cave, Spain
## 3 Results
### Microclimatology
In the H-11 hall, the air temperature ranged between 19.75 and 19.92 \({}^{\circ}\)C (\(m\) = 19.86 \({}^{\circ}\)C) so the difference between the maximum and minimum temperatures was lower than 0.2 \({}^{\circ}\)C (Table 1). The air CO\({}_{2}\) content ranged from 499 to 986 ppmv, with a mean value of 633 ppmv. The air relative humidity was 100% during all the studied period. In H-8 intermediate values of air temperature (\(m\) = 19.40 \({}^{\circ}\)C) and relative humidity (\(m\) = 95%) were recorded. In this case, the air CO\({}_{2}\) content ranged from 512 to 1170 ppmv, with a mean value of 699 ppmv. Therefore: (1) the air of the tourist sector is colder, less wet, and has a higher CO\({}_{2}\) content than in that of the nonvisited galleries of Nerja Cave, (2) the temperature and relative humidity variability is noticeably reduced in the nonvisited sector, located below greater thickness of rock and at greater distances from the cave entrances (E1, E2 and E3 in Figure 1), and (3) the variation coefficients (\(v\) in Table 1) in the external media are higher than in the cave, except for air CO\({}_{2}\). Figure 2 shows the temporal evolution of the main environmental parameters relative to the external air and cave air during 2016 and 2017. In summer, the temperature of the external air (T\({}_{\rm ext}\)) is higher than that of the cave air (T\({}_{\rm int}\)), and the latter is denser than the exterior (Figure 2A,B). CO\({}_{2}\) concentrations in the Touristic Galleries (Figure 2C) reach maximum values, coinciding with a lower index of natural ventilation (daily average values of \({}^{222}\)Rn over the 400 Bq/m\({}^{3}\), Figure 2A) and a greater number of visitors (Figure 2B). Air relative humidity is high in the cave, with values ranging between 95 and 100% (Figure 2D). When the external temperature markedly exceeds the cave temperature (\(\Delta\)T \(>\) 5.0 \({}^{\circ}\)C) the DAF-mode ventilation is activated (yellow orange bars in Figure 2). The cave air, denser than the external air, is blown out by the lowest entrances, and atmospheric air is sucked in by the highest entrances. During the day corresponding to the summer campaign (9 July 2016), \(\Delta\)T was 7.53 \({}^{\circ}\)C (daily average value). In winter, the external air is generally colder and denser than the cave air, although exceptionally short-term periods exist in which T\({}_{\rm ext}\) \(>\) T\({}_{\rm int}\) (Figure 2 A,B). CO\({}_{2}\) concentrations inside the Touristic Galleries are minimal and much more similar to those of the external atmosphere (Figure 2C), given the more effective natural ventilation (daily average values of \({}^{222}\)Rn of 80 Bq/m\({}^{3}\)) and lower number of visitors. Cave air relative humidity is minimum in the Touristic Galleries and shows the same temporal evolution than the external air (Figure 2D). When T\({}_{\rm ext}\) \(<\) T\({}_{\rm int}\), the external air, denser and colder than the internal air, easily enters Nerja Cave through the lowest entrances, moves through the Touristic Galleries, arrives at the High and New Galleries (the same day or 1-2 days later), and finally leaves the cave through Pintada Cave. During the day corresponding to the winter campaign (12 January 2017), the daily average value of \(\Delta\)T was \(-\)5.30 \({}^{\circ}\)C.  
Figure 2: Daily evolution from 01/01/16 to 31/12/17 of (**A**) external and cave air temperatures in Nerja Cave versus air \({}^{222}\)Rn concentration in H-4 (average for the period 2008–2013); (**B**) daily visitors versus air temperature differences (\(\Delta\)T = T\({}_{\text{ext}}\) - T\({}_{\text{int}}\)); T\({}_{\text{ext}}\): external air temperature; T\({}_{\text{int}}\): internal air temperature (H-4); (**C**) air CO\({}_{2}\) content. Data of external air CO\({}_{2}\) correspond to year 2018 and (**D**) external and cave air relative humidity. Blue bars: winter ventilation period, UAF-mode. Yellow orange bars: summer ventilation period, DAF-mode.