Influence of polycyclic aromatic hydrocarbon pollution on the diversity and function of bacterial communities in urban wetlands

Identification of key anthropogenic and land use factors and ecological risk assessment of dissolved polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in an urbanized estuary in China

This study investigated dissolved PAHs and OCPs in Quanzhou Bay estuaries, assessed their ecological risk, and examined anthropogenic impacts on contaminant distribution. Results showed that dissolved ∑24PAH concentrations ranged from 117 to 709 ng/L (mean: 358 ng/L), with dominance of 2-ring PAHs (Naphthalene, 1-Methylnaphthalene, and 2-Methylnaphthalene). Dissolved DDT levels ranged from 0.06 to 0.49 ng/L (mean: 0.28 ng/L), while HCBz concentrations varied from 0.02 to 0.44 ng/L (mean: 0.20 ng/L). PAHs were higher in the north due to urbanization and transport, while OCPs showed higher levels in the south due to historical agricultural use. Rural areas, water bodies, and wetlands significantly influenced the behavior of PAHs according to Spearman correlation and lasso regression analyses. Quanzhou Bay was categorized as a low to medium risk area based on dispersion simulation and ecological risk assessment, highlighting implications for future sustainable development and policy planning. CAPSULE: The coupled relationship between human activities and the distribution of dissolved PAHs and OCPs in urbanized estuaries was explored using statistical methods and GIS technology, providing valuable insights into environmental processes and pollutant control policies.

Contrasting benthic bacterial and fungal communities in two temperate coastal areas affected by different levels of anthropogenic pressure

Benthic microbial communities play a crucial role in maintaining the stability and function of estuarine ecosystems. However, their organization and response to multiple stresses in severely disturbed coastal areas remains to be elucidated. In this study, we revealed the presence of contrasting benthic bacterial and fungal communities in the Liaohe (LH) and Yalujiang (YLJ) estuaries, which are located at similar latitudes and are characterized by similar climates but are subjected to different levels of anthropogenic pressure. The results showed that Firmicutes and Chloroflexi were more abundant in LH, which reflected the influence of anthropogenic pressure in this area. Functional analyses indicated that the functional genes involved in the generation of precursor metabolites and energy pathways were more enriched in the LH community, while genes regulating degradation/utilization/assimilation processes were more enriched in the YLJ community. Distance-dependent similarity analysis showed that the bacterial community in LH was more affected by environmental changes, while that in YLJ was more influenced by geographic dispersion. In contrast, no significant distance-dependent similarity was found for the fungal communities in the two areas. In addition, the network analysis showed that the bacterial-fungal network in YLJ was more complex and stable than that in the LH. Our results highlight the important roles of environmental heterogeneity in controlling microbial community composition, biogeographic patterns, and co-occurrence networks. These findings fill knowledge gaps in the understanding of the different response patterns of benthic communities under varying anthropogenic pressures.

Deep relationships between bacterial community and polycyclic aromatic hydrocarbons in soil profiles near typical coking plants

Bacterial communities play an important role in maintaining the normal functioning of ecosystems; therefore, it is important to understand the effects of polycyclic aromatic hydrocarbons (PAHs) on the bacterial community. In addition, understanding the metabolic potential of bacterial communities for PAHs is important for the remediation of PAH-contaminated soils. However, the deep relationship between PAHs and bacterial community in coking plants is not clear. In this study, we determined the bacterial community and the concentration of PAHs in three soil profiles contaminated by coke plants in Xiaoyi Coking Park, Shanxi, China, using 16S rRNA and gas chromatography coupled with mass spectrometry, respectively. The results show that 2 ~ 3 rings PAHs are the main PAHs and Acidobacteria (23.76%) was the dominant bacterial community in three soil profiles. Statistical analysis showed that there were significant differences in the composition of bacterial communities at different depths and different sites. Redundancy analysis (RDA) and variance partitioning analysis (VPA) illustrate the influence of environmental factors (including PAHs, soil organic matter (SOM), and pH) on the vertical distribution of soil bacterial community, and PAHs were the main factors affecting the bacterial community in this study. The co-occurrence networks further indicated correlations between bacterial community and PAHs and found that Nap has the greatest effect on bacterial community compared with other PAHs. In addition, some operational taxonomic units (OTUs, OTU2, and OTU37) have the potential to degrade PAHs. PICRUSt2 (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) was used for further study on the potential of microbial PAHs degradation from a genetic perspective, which showed that different PAH metabolism genes were present in the genomes of bacterial communities in the three soil profiles, and a total of 12 PAH degradation-related genes were isolated, mainly dioxygenase and dehydrogenase genes.

The diversity and function of the in-situ fungal communities in response to polycyclic aromatic hydrocarbons in the urban wetland

PAHs (polycyclic aromatic hydrocarbons) increases the potential harm to ecosystem and human health. The fungi is considered as a powerful choice for degradation of PAHs. The researches on the effect of PAHs on fungal population in sediment/soil mostly stayed in the laboratory simulation that is based on extreme pollution. This study investigated the fungal population of the urban wetland by high-throughput sequencing in-situ micro-pollution state. Our statistical analysis revealed significant difference in the whole fungal population at the phylum among three land use types in typical urban wetland. Among them, Ascomycota was the dominant fungi at the phyla in three land use types. Fungal genus of degrading PAHs were significantly correlated with Dibenz[a, h]anthracene (P = 0.018) in ditch wetland, Total Organic Carbon (P = 0.02) and Fluoranthene (P = 0.04) in riverine wetland, and Electrical Conductivity (P = 0.018) in agricultural land. PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) suggested that 20 enzymes were present related to PAHs metabolism in three land use types. Specifically, monoxygenase, dehydrogenase, and laccase were most abundant among inferred enzymes, indicating that the urban wetland had potential for the degradation of PAHs. This study contributed to in-depth understanding of the structure and function of fungal population and provided a theoretical basis for PAHs microbial remediation in the in-situ environment.

Microbial Community Succession Associated with Poplar Wood Discoloration

Microbes are common inhabitants of wood, but little is known about the relationship between microbial community dynamics during wood discoloration. This study uses simulation experiments to examine the changes in the microbial communities in poplar wood at different succession stages. The composition and structure of the microbial communities changed significantly in different successional stages, with an overarching pattern of bacterial diversity decreasing and fungal diversity increasing from the early to the late successional stages. Nevertheless, succession did not affect the composition of the microbial communities at the phylum level: Proteobacteria and Acidobacteria dominated the bacterial communities, while Ascomycota and Basidiomycota dominated the fungal communities. However, at the genus level, bacterial populations of Sphingomonas and Methylobacterium, and fungal populations of Sphaeropsis were significantly more prevalent in later successional stages. Stochastic assembly processes were dominant in the early successional stages for bacteria and fungi. However, variable selection played a more critical role in the assembly processes as succession proceeded, with bacterial communities evolving towards more deterministic processes and fungal communities towards more stochastic processes. Altogether, our results suggest that bacteria and fungi exhibit different ecological strategies in poplar wood. Understanding those strategies, the resulting changes in community structures over time, and the relationship to the different stages of poplar discoloration, is vital to the biological control of that discoloration.

Crude Oil Degradation by a Novel Strain Pseudomonas aeruginosa AQNU-1 Isolated from an Oil-Contaminated Lake Wetland

In this study, a novel crude oil degrading bacterium was isolated from an oil-contaminated freshwater lake using crude oil as the sole carbon source. The strain was named Pseudomonas aeruginosa AQNU-1 based on the analyses of its morphological characteristics and 16S rRNA gene sequencing. Gas chromatography-mass spectrometry (GC-MS) was carried out to investigate the degradation of crude oil fractions under dynamic (37 °C, 180 r/min) and static (37 °C, 0 r/min) cultivation over three months of continuous enrichment in the laboratory. It was found that strain AQNU-1 exhibited stronger biodegradation efficiency for n-alkanes of C13–C35 under dynamic cultivation with degradation ratios of 87–100% compared to ratios of 74–100% under static cultivation. Furthermore, this strain could fully utilize alkylcyclohexane (M/Z 82), alkylbenzene (M/Z 92) and alkyltoluene (M/Z 106) in crude oil under both conditions. It also had better biodegradability of partial aromatic compounds in the crude oil, showing differences within compound families of aromatic hydrocarbons. Further, the potential degradation ability of this isolated strain decreased with increasing molecular weight, with the dynamic condition performing better in general. These results suggest that the isolated strain has great potential to assimilate indigestible crude-oil contaminants under different hydrological conditions, providing a valuable microbiological resource for in situ remediation of natural wetlands.