# Diversity and Seasonal Dynamics of Airborne Fungi in Nerja Cave, Spain
## 4 Discussion
During the winter campaign, the difference \(\Delta\)T is negative. The colder and denser external air enters Nerja Cave through the lower entrances (E1, E2 and E3 in Figure 1) and moves from the tourist to nontourist sector (UAF-mode). So, the strong ventilation during this period contributes to the entry of atmospheric air inside the cave, to its rapid exit through the Pintada Cave, and thus, to the rapid renovation of the air cave. This is exemplified by the abundant occurrence of _Cladosporium cladosporoides, Aspergillus spleaeus, and Penicillin flavigenum_ in the halls of the Touristic Galleries and outside. _Parengyodontium album_ (syn. _Engyodontium album, Beauveria alba, Trititachium album_) [33], identified only in summer, was limited to the air of the visited area (Touristic Galleries), which could correspond to the presence of insects in spring and summer, since the fungus is a parasite of arthropods, and also to the presence of phototrophic biofilms in these galleries. [PERSON] et al. [34] found this species only in the air of the cave, but not in the sediments. [PERSON] et al. [35] and [PERSON] et al. [36] reviewed the entomopathogenic fungi related to cultural heritage sites and associated _Pa. album_ with the presence of arthropods. This was also reported in Lascaux Cave [37]. Data on the role of fungi in caves suggested that the species related to arthropods contribute to their mortality and favor the dispersal of spores. [PERSON] et al. [35] recommended the control of arthropod populations as a method to reduce fungal contamination and colonization of substrates, sediments, and rocks [35]. The spores of _Pa. album_ were also widely distributed in the air of Castanar de Ibor, Ardales, Gruta de las Maravillas, and Tesoro caves [30; 38; 39]. In addition, _Pa. album_ is common in other subterranean environments [40; 41; 42; 43] and wall paintings, and in this last case associated to arthropods [44; 45; 46]. A review on cave fauna reported the presence of many different classes of arthropods in Nerja, including endemisms [47]. The abundant presence of spores of _Pa. album_ and other entomopathogenic fungi in the air in Ardales and Tesoro caves [30] emphasizes the likely role of arthropods as a vector of these fungi. The genus _Aspergillus_ is one of the most abundant in the air of Nerja Cave. _Aspergillus_ showed greater diversity in winter, with the species _A. versicolor, A. spaleaus, A. baeticus, A. ustus, A. pulvericola, A. welwitschiae, A. oryzae_, and _A. ochraceus_, while in summer were only recovered _A. versicolor_ and _A. spaleaus_. The abundance of _Aspergillus_ was shown in previous publications, although the species could not be identified due to the protocol used [26; 27]. [PERSON] et al. [32] isolated 72 fungi from sediments and air in Nerja, among them 18 different species of _Aspergillus_, from which two were only present in the air and three in both sediments and air. This suggests that an important source of _Ascomycata_ in the cave, the sediments, could not be disregarded. We isolated seven species of _Aspergillus_ from the cave air, and the most abundant species present in the two seasonal samplings were _A. versicolor_, _A. spaleaus_, _A. ustus_, and _A. baeticus_. The first two showed a marked seasonality, so while _A. versicolor_ was abundant in summer and scarce in winter, _A. spaleaus_ showed the inverse trend, being highly represented in almost all the halls in winter and occasionally in summer (8.7% in Kitchen Hall). According to [PERSON] et al. [48]_A. versicolor_ is a xerotolerant species frequently detected even in extreme environments. _Aspergillus versicolor_ was relatively common in the air of caves all over the world [49; 50; 51; 52; 53; 54; 10], while _Aspergillus ustus_ presented a more restricted distribution [55; 56; 50; 49; 52]. _Aspergillus versicolor_, relatively abundant outside in winter, was only found in the deepest Mountain Hall. Thus, according to the ventilation mode of the winter period (UAF-mode), their relationship with the external atmosphere is discarded.