Microbially-Enhanced Weathering in Subsurface Habitats: Sulfur-Oxidizing Bacteria and The Cave Environment
While most caves and karst features form from carbonic acid dissolution of carbonate rocks, caves can also form by sulfuric acid dissolution (Egemeier, 1981). Sulfuric acid is derived from hydrogen sulfide-rich waters that rise up into carbonate strata and become oxidized: 1) through abiotic reactio...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.500.5077 http://www.karst.edu.cn/karst/igcp/igcp448/2002/3-3-1.pdf |
| Summary: | While most caves and karst features form from carbonic acid dissolution of carbonate rocks, caves can also form by sulfuric acid dissolution (Egemeier, 1981). Sulfuric acid is derived from hydrogen sulfide-rich waters that rise up into carbonate strata and become oxidized: 1) through abiotic reactions from mixing of waters having different concentrations of hydrogen sulfide or mixing reduced and oxygen-rich waters (Palmer, 1995), as well as 2) from biological oxidation reactions (Altas & Bartha, 1998). One of the major problems interpreting caves formed by sulfuric acid speleogenesis is recognizing the mechanisms of sulfuric acid formation. However, in modern caves containing sulfidic waters, there is a wide range of microorganisms in these systems. A vast majority of them are sulfur-oxidizing bacteria that live within cave springs and streams, as well as growing on cave-wall surfaces (Table 1). Some of these bacteria are reportedly acidophilic due to the production of sulfuric acid (Hose & Piscarowicz, 1999; VlÇsceanu et al., in press). Therefore, sulfur-oxidizing bacterial populations can be examined as a means of understanding sulfuric acid speleogenesis. Additionally, studying the microbial communities in sulfidic caves can provide a better appreciation of other sulfidic habitats, relative microbial abundance and viability in the subsurface, and potential biogeochemical interactions pertinent to global sulfur cycling. Unfortunately, although sulfur-oxidizing microorganisms have been identified, few studies have addressed the possible geomicrobiological impacts that the microbial communities may have on the cave environment. For these reasons, this work examined sulfur-oxidizing bacterial populations from four sulfidic cave systems and tested whether their metabolic activity can enhance cave formation and modification. |
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