Abstract
The effects of the unpredictability of the flow system in a karst area, with respect to bacterial communities in the aquatic environment, were evaluated. Bacterial communities from two different types of flow conditions (spring and sinkhole) were characterized and compared in the karst area. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the major phyla present in the sampled spring and sinkhole waters. The water samples from the spring points were heavily loaded with Actinobacteria, especially Firmicutes, which accounted for 4.3% of the bacterial content. Furthermore, Actinobacteria were prevalent in some water samples, serving as indicators of the effects of seawater inundation. The richness and diversity of bacterial species were evaluated at the spring and sinkhole water points. The spring waters showed a higher bacterial richness and diversity compared to the sinkhole waters. Our results provide valuable information for the evaluation and investigation of microbial compositions in karst areas, which are characterized by heterogeneous hydrological conditions. The microbial species in karst areas are already exposed to changing hydrogeological conditions, and are likely to be confronted with future changes; thus, their spatiotemporal variations reflect the shifting baselines of physicochemical and ecosystem processes.
Highlights
Karst regions contain abundant exposures of limestone or dolomite above the erosion surface, and a well-developed groundwater system formed by the erosion of these rock bodies
The 16S Ribosomal Ribonucleic Acid (rRNA) was amplified by Polymerase Chain Reaction (PCR) for multiplexed pyrosequencing using barcoded primers
The occurrence of Ca–Mg–SO4 in the study area is very unlikely to be attributed to the hydrogeological characteristics of the karst area, and it is probably effected by anthropogenic activities
Summary
Karst regions contain abundant exposures of limestone or dolomite above the erosion surface, and a well-developed groundwater system formed by the erosion of these rock bodies. Carbonate regions account for approximately 20% of the Earth’s surface [3], and many of these regions utilize groundwater for daily water supply [4]. Previous research has analyzed the hydrological characteristics and flow patterns of groundwater in carbonate regions [5,6]. These characteristics are observed in some limestone regions of Gangwon-do (Samcheok, Yeongwol, Jeongseon and Sokcho) and the northern parts of Chungcheongbuk-do (Danyang-gun) in Korea.
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