Diatoms – invisible residents of Resavska Cave (eastern Serbia)

Abstract

Diatoms (Bacillariophyta) are widespread microorganisms that were found in different aquatic ecosystems, but also in other habitats, such as stone substrates exposed to air. There diatoms thrive with other phototrophic organisms (cyanobacteria and algae) if they have sufficient sunlight, water and nutrients. Phototrophic organisms penetrate into tourist caves where artificial lights support their growth. This community in the vicinity of lights, so called lampenflora, includes bacteria, cyanobacteria, algae, fungi, mosses and lichens. Despite cave diatoms in Serbia have been studied several times, the knowledge about this group is scarce. Epilithic diatoms were collected by scraping biofilms from the entrance (two sampling sites) and the inside (four sampling sites) of Resavska Cave (eastern Serbia). Since the Resavska Cave is famous show cave, higher diversity of all phototrophs, not only diatoms is expected because of artificial light, but also due to the presence of the tourists that can introduce different microorganisms from the outside environment. A total of 24 diatom species from 10 genera were identified. The most frequent and abundant genera are Humidophila (12 species) and Sellaphora (3 species), while others (Cyclotela, Fallacia, Diadesmis, Luticola, Nitzschia, Orthoseira, Simonsenia, Tryblionella) count one to two species. This cave is mostly populated by aerophytic and cosmopolitan species such as Humidophila contenta, Humidophila paracontenta and Humidophila perpusila that were present at the entrance and inside the cave. Beside of Humidophila representatives, species Fallacia insociabilis, Diadesmis biceps, Sellaphora nigri and Sellaphora saugerresii were registered inside the cave in low abundance. Inside the cave, at sampling site with dripping water Cyclotella sp. and Luticola sp. were documented. Entrance of the cave includes ten species which were recorded inside as well, except for the Humidophila aerophila which was found only at the entrance.