Karst pools in subsurface environments: collectors of microbial diversity or temporary residence between habitat types

Abstract

We studied bacterial diversity and community composition in three shallow pools of a Swiss karst cave system with contrasting hydrological and hydrochemical properties. The microbial assemblages in the pools were remarkably different, and only one operational taxonomic unit of 16S rRNA genes (OTU, 97% similarity) was shared between the three of them (total OTU number in all pools: 150). Unexpectedly high microbial phylotype richness was found even in the two pools without groundwater contact and with low concentrations of organic carbon and total cell numbers (< 10(4) ml(-1)). One of these seepage water fed systems harboured 15 distinct OTUs from several deeply branching lineages of the candidate phylum OP3, whereas representatives of this group were not detected in the other two pools. A tentative phylogeographic analysis of available OP3-related sequences in the context of our data set revealed that there was generally little agreement between the habitats of origin of closely related sequence types. Two bacterial clades affiliated with the obligate methylamine utilizer Methylotenera mobilis were only found in the pool that was exposed to repeated flooding events. These bacteria formed relatively stable populations of up to 6% of total cell counts over periods of several months irrespective of inundation by groundwater. This suggests that karst water may provide a means of transport for these bacteria from terrestrial to freshwater habitats.

Microbial diversity and impact on carbonate geochemistry across a changing geochemical gradient in a karst aquifer

“…Microbial processes focused at water-rock interfaces can significantly affect karstification and the flux of dissolved constituents through and out of the system, especially when solutions are near-equilibrium with bedrock minerals (Compton and Pritchard, 1990;White, 1997;Ehrlich and Newman, 2009). Although changes in microbial community composition from karst springs has been linked to storm-induced flow conditions (see, e.g., Pronk et al, 2009), and cave microbial diversity can determine potential transport history through karst (Shabarova and Pernthaler, 2010), quantification of microbial controls on geochemistry and potential karst aquifer modification has been limited. In this study, we expand our previous work (Engel et al, 2004;Engel and Randall, 2011) to expose a persistent link between geochemistry and microbial community composition from wells that cross the fresh to saline water transition zone in the Edwards Aquifer.…”

Sustained Anthropogenic Impact in Carter Saltpeter Cave, Carter County, Tennessee and the Potential Effects on Manganese Cycling

“…Localized variations in geochemistry and nutrient availability have been shown to impact microbial community structure (Johnston et al, 2012;Barton and Jurado, 2007;Shabarova and Pernthaler, 2010) and niche diversification (Engel et al, 2010;Macalady et al, 2008). Further, the composition of cave microbial communities mediates and stabilizes biogeochemical cycling and mineralization processes within an environment (Portillo and Gonzalez, 2010;Portillo et al, 2009).…”

Microbial communities in a coastal cave: Cova des Pas de Vallgornera (Mallorca, Western Mediterranean)

“…In the molecular survey performed by Pasic et al (2010) members of the Gammaproteobacteria were most abundant in the clone libraries, followed in abundance by members of Actinobacteria. Proteobacteria predominated also in the study of Shabarova & Pernthaler (2010).…”