Hydrostatic pressure influence activity and assembly of bacterial communities in reservoir sediments

Abstract

Reservoir sediments are subjected to highly variable hydrostatic pressures, but little is known about the direct impacts of this environmental variable on microbial communities and biogeochemical processes mediated by microbes in the numerous deep reservoirs (>100 m) scattered across our planet. To address this gap, the organic matter degradation and community assembly of sediment bacteria were studied in bioreactors maintained under different hydrostatic pressures (0.5–3.0 MPa) and explored using 16S rRNA amplicon sequencing analysis. Our results showed that rates of CO2 and CH4 production and microbial activity decreased significantly with increasing pressure, at least when exceeding 1.0 MPa. In contrast, α‐diversity and community structure of the active (16S rRNA) and total (16S rRNA gene) bacterial communities did not show any significant response to the different hydrostatic pressures, but a co‐occurrence network demonstrated that interactions between bacterial populations were stronger at higher pressures (≥1.5 MPa). Moreover, ecological null model analyses revealed that when the pressure exceeded 1.5 MPa, the main assembly processes of bacterial communities changed from stochastic to deterministic. These findings corroborate an important role of pressure in the assembly and emerging interactions within sediment bacterial communities. Our results imply that increased hydrostatic pressure caused by dam constructions may hamper the metabolism of the sediment microbiota, and that this may result in enhanced sediment burial of nutrients and organic matter, at least when pressures exceed 1.0 MPa.

Microbial Community Structure and Ecological Networks during Simulation of Diatom Sinking

“…ANOSIM (analysis of similarity) further demonstrated that there were significant differences in microbial communities at different pressures ( Table S5 ). These findings are consistent with findings from previous pressure incubation experiments with surface seawaters [ 36 ], sediments [ 64 ], and sinking POM [ 20 , 29 ].…”

“…Our results suggest a significant decrease in microbial diversity under HHP and LT conditions ( Figure 1 ). One possible explanation is that the metabolic activity and cellular processes of microbial communities seem to be inhibited by HHP and LT; therefore, a large number of microbial cells may die or tend to be dormant under unfavorable environments [ 30 , 32 , 64 , 65 ]. Similar variation trends were observed in microbial communities of pressure-induced sediment samples [ 64 ] and during sinking particles degradation [ 30 ].…”

“…HHP and LT are important environmental factors in shaping the structure and complexity of microbial networks [ 64 ]. We found that the PAM and FLM networks became more complex with POM sinking, as indicated by their increased connectivity (avgK), tightest clusters (avgCC), and shortest GD with increasing pressure and decreasing temperature.…”