Effects of Polycyclic Aromatic Hydrocarbons on the Composition of the Soil Bacterial Communities in the Tidal Flat Wetlands of the Yellow River Delta of China

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are pervasive organic pollutants in coastal ecosystems, especially in tidal flat wetlands. However, the mechanisms through which PAHs impact the soil bacterial communities of wetlands featuring a simple vegetation structure in the Yellow River Delta (China) remain largely unclear. In this study, we examined soil samples from two sites featuring a single vegetation type (Suaeda salsa) in the Yellow River Delta. Specifically, we investigated the impacts of PAHs on the diversity and composition of soil bacteria communities through high-throughput 16 S rRNA sequencing. PAHs significantly increased the soil organic carbon content but decreased the total phosphorus content (p = 0.02). PAH contamination notably reduced soil bacterial community α diversity (Shannon index) and β diversity. Furthermore, PAHs significantly altered the relative abundance of bacterial phyla, classes, and genera (p < 0.05). Specifically, PAHs increased the relative abundance of the bacterial phyla Acidobacteriota and Gemmatimonadota (p < 0.05), while decreasing the relative abundance of Bacteroidota, Desulfobacterota, and Firmicutes compared to the control wetland (p < 0.05). Moreover, PAHs and certain soil properties [total nitrogen (TN), soil organic carbon (SOC), total phosphorus (TP), and total salt (TS)] were identified as key parameters affecting the community of soil bacteria, with the abundance of specific bacteria being both negatively and positively affected by PAHs, SOC, and TN. In summary, our findings could facilitate the identification of existing environmental problems and offer insights for improving the protection and management of tidal flat wetland ecosystems in the Yellow River Delta of China.

Keywords: bacterial community; contamination; diversity; wetland ecosystems.

Figure 1

PCoA of PHA-contaminated and non-contaminated wetland soils in the Yellow River Delta, China. CK, non-polluted wetland; PAH-polluted wetland.

Figure 2

The relative abundances of bacterial operating taxonomic units (phyla, classes, and genera) exhibited significant differences between the two wetlands ((a–c) and Table S1).

Figure 2

The relative abundances of bacterial operating taxonomic units (phyla, classes, and genera) exhibited significant differences between the two wetlands ((a–c) and Table S1).

Figure 2

The relative abundances of bacterial operating taxonomic units (phyla, classes, and genera) exhibited significant differences between the two wetlands ((a–c) and Table S1).

Figure 3

RDA of soil bacterial community structures and physicochemical properties (arrows) of PHA-contaminated and non-contaminated wetland soils in the Yellow River Delta, China.

Figure 4

Correlation between the physicochemical properties of soil and the abundance of soil bacterial phyla (a), class (b), and genera (c) in PHA-contaminated and non-contaminated wetland soils in the Yellow River Delta, China. The * indicated the significant different at 0.05 level; The ** indicated the significant different at 0.01 level; The *** indicated the significant different at 0.001 level.

Figure 4

Correlation between the physicochemical properties of soil and the abundance of soil bacterial phyla (a), class (b), and genera (c) in PHA-contaminated and non-contaminated wetland soils in the Yellow River Delta, China. The * indicated the significant different at 0.05 level; The ** indicated the significant different at 0.01 level; The *** indicated the significant different at 0.001 level.

Figure 4

Correlation between the physicochemical properties of soil and the abundance of soil bacterial phyla (a), class (b), and genera (c) in PHA-contaminated and non-contaminated wetland soils in the Yellow River Delta, China. The * indicated the significant different at 0.05 level; The ** indicated the significant different at 0.01 level; The *** indicated the significant different at 0.001 level.