Historical exposure to wastewater disposal reinforces the stability of sediment bacterial community in response to future disturbance

Given that long-term treated wastewater discharge may alter the microbial community of the recipient coast, it is important to evaluate whether and how the community's stability is impacted. We constructed microcosms using coastal sediments with (near-coast) and without (far-coast) a wastewater disposal history and compared the communities’ responses to p-chloroaniline (PCAN, a typical organic pollutant) in low (10 mg/L) and high (100 mg/L) concentrations. Compared to the far-coast community, the near-coast community drove faster PCAN attenuation and nitrate generation. More significant negative correlations were observed between the alpha-diversity indices and PCAN concentrations in the far-coast communities than the near-coast ones. The community turnover rate, represented by the slopes of the time–decay curves, was slower for the near-coast community (−0.187) than that for the far-coast community (−0.233), but only when the PCAN was added in low concentration. Our study revealed that the long-term wastewater disposal may cause the sediment bacterial community to be less sensitive and more stable in response to a future disturbance, demonstrating a significant historical effect of environmental context on the coastal microbial community's stability.

The Effect of G-C3N4 on Bacterial Community in Sediment of Xiang River Under Tetracycline Pressure

As photocatalysts applied more and more often to treat pollutants by photocatalytic reactions, they may enter the environment via water spreading. Although there are some investigations about their influence on different organisms, little is known about its impact on the ecological microenvironment. To understand how photocatalysts effect sediment ecological microenvironment in the process of pollution remediation, the impact of typical photocatalyst g-C3N4 (Graphitic carbon nitride) on rivered sediment community polluted by typical antibiotic tetracycline (TC) was investigated. The sediment samples were exposed to different concentrations of TC, g-C3N4 or TC/g-C3N4 (exposed to 60, 120, 180 mg/L TC, or 25, 75, 125 mg/kg g-C3N4, or 25, 75, 125 mg/kg g-C3N4 plus 60, 120, 180 mg/L TC, respectively), and sediment bacterial community were analyzed by Illumina sequencing. The results indicated that the dominant bacterial phyla in the samples were Acidobacteriota, Proteobacteria, Actinobacteriota, Chloroflexi. The diversity and richness of microorganisms in riverbed sediment were increased a little bit by g-C3N4 with different concentrations, which reached the highest value when exposed to 75 mg/kg g-C3N4. g-C3N4 lightly increased the percentage of relative abundance of Cyanobacteria. The bacterial communities’ structure of the samples treated with TC, g-C3N4 or TC/g-C3N4 were distinguishable. g-C3N4 alone had little effect on microbial structure, while TC/g-C3N4 had medium influence and TC had great impact on it. Under TC stress, g-C3N4 slowed down the growth of Cyanobacteria to some extent and restored the changes of bacterial community structure caused by TC, and reduced the residual TC in water body, thus eliminating the side effects of TC. The result shown that g-C3N4 could significantly reduce the residue of TC in riverbed sediment, without affecting the microbial ecology in the environment.

Stream sediment bacterial communities exhibit temporally-consistent and distinct thresholds to land use change in a mixed-use watershed

Freshwater ecosystems are susceptible to biodiversity losses due to land conversion. This is particularly true for the conversion of land from forests for agriculture and urban development. Freshwater sediments harbor microorganisms that provide vital ecosystem services. In dynamic habitats like freshwater sediments, microbial communities can be shaped by many processes, although the relative contributions of environmental factors to microbial community dynamics remain unclear. Given the future projected increase in land use change, it is important to ascertain how associated changes in stream physico-chemistry will influence sediment microbiomes. Here, we characterized stream chemistry and sediment bacterial community composition along a mixed land-use gradient in West Virginia, USA across one growing season. Sediment bacterial community richness was unaffected by increasing anthropogenic land use, though microbial communities were compositionally distinct across sites. Community threshold analysis revealed greater community resilience to agricultural land use than urban land use. Further, predicted metagenomes suggest differences in potential microbial function across changes in land use. The results of this study suggest that low levels of urban land use change can alter sediment bacterial community composition and predicted functional capacity in a mixed-use watershed, which could impact stream ecosystem services in the face of global land use change.

Long-Term Combined Effects of Crude Oil and Dispersant on Sediment Bacterial Community

To better understand long-term combined effects of crude oil and dispersant on bacterial community, sediments microcosms were set up in triplicates and treated with dispersant (Corexit 9500A), crude oil, and Corexit 9500A plus crude oil. After 60 days exposure, there was a significant change in the bacterial community structure in all treatments. The shift in the bacterial community structure in Corexit 9500A plus crude oil treatment was considerably different from those by either Corexit 9500A or crude oil. DNA sequence analysis showed that Hydrocarboniphaga effuse, Parvibaculum lavamentivorans,and Alicyclobacillus ferrooxydans were the major bacterial species in crude oil treatment. Pandoraea thiooxydans, Janthinobacterium sp. and Hyphomicrobium nitrativorans were the most dominant species in Corexit 9500A treatment. The species Janthinobacterium sp., Parvibaculum lavamentivorans, and Dyella sp. were enriched in Corexit 9500A plus crude oil treatment. The majority of the detected species were hydrocarbons degraders. The study showed that Corexit 9500A addition enhanced the biodegradation rate by increasing the diversity and richness of hydrocarbons degrading species. Corexit A9500 application should be considered during crude oil spills to evaluate environmental impacts.