The Relationship between pH and Bacterial Communities in a Single Karst Ecosystem and Its Implication for Soil Acidification

Abstract

Enhanced monsoon duration and soil acidification from acid rain are expected to impact the distribution of microbial communities in surface and subsurface environments, although these impacts are poorly understood for most systems. In central China, soluble carbonate bedrock forms extensive karst landscapes. Current predictions are that the amount of monsoonal precipitation and acid rainfall in central China will increase, which is expected to lead to changes in the pH balance of karst ecosystems. To evaluate the role of pH, total organic carbon, and other geochemical parameters (e.g., Ca2+, Mg2+, NH4+, NOx, SO42-) in shaping bacterial communities within a single karst system in central China, samples were collected from the thin surface soils overlying Heshang Cave, cave sediments, and weathered cave passage rocks from the entrance, twilight, and dark zones, as well as from epikarstic drip waters inside the cave. Illumina sequencing of 16S rRNA genes and multivariate statistical analyses revealed that each tested community was distinct and the community variability was significantly correlated with pH, total organic carbon, and potassium concentrations. Specifically, surface soils were dominated by Acidobacteria, Verrucomicrobia and Planctomycetes, and diversity significantly decreased with acidic pH values. Nitrospirae, Gemmatimonadetes, Firmicutes, and Chloroflexi were unique to cave sediments, while Actinobacteria and Proteobacteria dominated weathered rocks and drip waters, respectively. The results reveal important implications regarding the effects of acidification on bacterial communities in karst areas, and on the control of pH in shaping bacterial communities throughout a karst system. Increased water flux into and through karst habitats due to monsoonal precipitation may result in deeper penetration of acidic solutions into karst and shift the bacterial communities inside the cave in the future.

Soil pH Is the Primary Factor Correlating With Soil Microbiome in Karst Rocky Desertification Regions in the Wushan County, Chongqing, China

“…We find that soil pH is the main factor that correlates with soil bacterial community. Our results agree with numerous previous studies (Lauber et al, 2009 ; Rousk et al, 2010a , b ; Yun et al, 2016 ). The overall close relationship of pH with bacterial community is due to most of bacteria having rather narrow pH optima (Charokopos et al, 2010 ).…”

The Soil Microbiome of the Laurel Forest in Garajonay National Park (La Gomera, Canary Islands): Comparing Unburned and Burned Habitats after a Wildfire

“…Contrary to Acidobacteria, higher C mineralization rates positively correlate with the abundance of Betaproteobacteria and Bacteroidetes [54]. Consistent with previous reports that showed a predominance of Proteobacteria in many types of soils, [52,55,62,63], they were an abundant phylum in the soils of the Garajonay laurel forest. Moreover, coinciding with other frequent post-fire effects described in other forests, the previous dominance of Alphaproteobacteria was greatly diminished [13,18,21] in favor of Betaproteobacteria [13,18,20,54,64] in burned soil.…”

Spatial and temporal dynamics of bacterioplankton community composition in a subtropical dammed karst river of southwestern China

“…Notably, temperature exerts significant positive or negative effects on pH, DO, and nutrition, which in turn cast the influences on bacterioplankton composition and alpha diversity (Figure ). pH is a major environmental determinant shaping the patterns of bacterioplankton biodiversity and bacterioplankton community structures (Yun et al., ); however, we have very limited information about the patterns and processes by which overall bacterioplankton communities assemble across wide pH gradients in karst waters (Ren et al., ). DO exerts a direct negative effect on bacterioplankton composition, thus contributing to the shape of community structures of anoxygenic and oxygenic phototrophic bacteria in the dammed Liu River (Taipale, Jones, & Tiirola, ).…”