Bacterial community structure and dissolved organic matter in repeatedly flooded subsurface karst water pools

Abstract

Bacterial diversity, community assembly, and the composition of the dissolved organic matter (DOM) were studied in three temporary subsurface karst pools with different flooding regimes. We tested the hypothesis that microorganisms introduced to the pools during floods faced environmental filtering toward a 'typical' karst water community, and we investigated whether DOM composition was related to floodings and the residence time of water in stagnant pools. As predicted, longer water residence consistently led to a decline of bacterial diversity. The microbial assemblages in the influx water harbored more 'exotic' lineages with large distances to known genotypes, yet these initial communities already appeared to be shaped by selective processes. β-Proteobacterial operational taxonomic units (OTUs) closely related to microbes from subsurface or surface aquatic environments were mainly responsible for the clustering of samples according to water residence time in the pools. By contrast, several Cytophagaceae and Flavobacteriaceae OTUs were related to different floodings, which were also the main determinants of DOM composition. A subset of compounds distinguishable by molecular mass and O/C content were characteristic for individual floods. Moreover, there was a transformation of DOM in stagnant pools toward smaller and more aromatic compounds, potentially also reflecting microbial utilization.

Detection of mycobacteria in the environment of the Moravian Karst (Bull Rock Cave and the relevant water catchment area): the impact of water sediment, earthworm castings and bat guano

“…The strongly-smelling alluvial sediments in these caves contain pieces of wood, foliage, and pine-needles mixed together with sand, and was studied by Kriz (1891;1892). The impact of alluvial sediments on geomicrobiology was investigated recently by Shabarova et al (2014). This study verified the hypothesis that the long-term residence of water in stagnant cave pools consistently led to a decline in bacterial diversity.…”

Dissolved organic carbon transformations and microbial community response to variations in recharge waters in a shallow carbonate aquifer

“…The increase in the C/A C ratio in the bulk of the samples suggests that the humic-like material at the water table comprises more humified, older organic molecules compared to the majority of the samples from the surface. This is similar to results for shallow stagnant cave pools where the microbial decomposition of organic matter transforms it to a more stable refractory form in older waters (Shabarova et al 2014). The increase in the C/A C ratio may indicate the longer residence time, and thus greater age, of groundwater at the top of the freshwater lens, compared to waters interacting with vegetation, the land surface and vadose zone during rapid recharge.…”

“…Recently, Shabarova et al (2014) showed a significantly decrease in concentration of humic and fulvic acids in cave pools, over a period of weeks, as a result of microbial activity. Our data demonstrate that fresh organic matter derived from terrestrial plants (e.g.…”

Proposed Guidelines for Solid Phase Extraction of Suwannee River Dissolved Organic Matter

“…This finding is important for the practical application in specific ecosystems in which DOC quality and concentrations may vary substantially. 37 Hence, the results above showed that DOC recovery and structures were quite uniform up to a DOC/PPL mass ratio of 1:200. We then have investigated the effects of variable DOC concentration at a fixed volume (6.25 mL) of SR DOM solution.…”