Characterization of Cave Aerophytic Algal Communities and Effects of Irradiance Levels on Production of Pigments

Aerophytic algae grow on various substrata under favourable ecological conditions. In the illuminated parts of caves, where relative humidity reaches 100%, they colonize sediments, rocky surfaces, and artificial materials. An aerophytic algal community from the cave entrance is composed almost exclusively of cyanobacteria, in contrast to lampenflora where green algae become more dominant. In the later stage of species succession in the lampenflora community, cyanobacteria are more abundant and thus community structure becomes more similar to the community from the cave entrance. Absence of correlation between photon flux density and chlorophyll a concentration indicates that substratum characteristics at the micro level notably influence algal growth. Chl a concentration per surface unit in the case of the epilithic algae from the cave entrance is lower (max. 1.71 mg cm22 ) compared to that for the lampenflora algae (max. 2.44 mg cm22 ). At cave temperatures, the light saturation point is quickly reached. At 9.0 uC and frequent low photon flux densities in a cave entrance and around lamps in show caves, biosynthesis of accessory photosynthetic pigments for two typical cave aerophytic organisms, cyanobacterium Chroococcus minutus and green alga Chlorella sp., is considerably elevated