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The STUDIA UNIVERSITATIS BABEŞ-BOLYAI issue article summary
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Abstract: Due to the absence of light belowground, and thus the consequent lack of photosynthetic plants, microorganisms and dead organic materials transported from the surface provide the basis of any groundwater food web. We aim to relate the abundance of microbial assemblages to the presence and density of groundwater fauna in the epikarst of Pădurea Craiului Mountains (NW Romania), and to determine whether the water dripping from the unsaturated zone of karst can be regarded as microbiologically and chemically clean. For that, we determined the density of aerobic heterotrophic bacteria, coliform microorganisms, and various microbial physiological groups (i.e. iron reducing bacteria, ammonifying bacteria, and denitrifying bacteria) in samples of water dripping in three caves. Our analyses revealed that the sampled groundwater is not contaminated by surface microflora, i.e., it is free of coliform microorganisms (Enterobacteriaceae). Although the estimation of the abundance of aerobic heterotrophic bacteria showed relatively low numbers of viable cells, other physiological tests revealed relatively larger numbers of iron reducers, ammonifying and denitrifying bacteria. The relative large number of microorganisms involved in the nitrogen cycle can be related to ammonification and denitrification processes occurring in the above-karst soils through which percolating water passes. In general, the abundance of microorganisms was larger in locations where there was a larger population density of groundwater fauna, and conversely, at locations with lower density of groundwater fauna, fewer microorganisms were detected.
Keywords: cave, groundwater fauna, microorganisms, Pădurea Craiului Mountains, unsaturated zone
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