江汉平原人口稠密区地表水和地下水细菌群落的时间动态变化

Temporal dynamics of bacterial communities in surface water and groundwater in the densely populated area of the Jianghan Plain

摘要:

【目的】 揭示江汉平原人口稠密区地表水和地下水细菌群落在旱季和雨季之间的动态变化，探究产生时间动态差异的原因。【方法】 于江汉平原人口稠密区的地表水、地下水采集水样，利用宏基因组测序技术，分析地表水和地下水细菌群落在环境条件、群落结构、群落构建过程的季节间变化差异。【结果】 地表水的盐度(P<0.01)、电导率(P<0.01)在雨季显著低于旱季，地下水的浊度(P<0.05)在雨季显著高于旱季，反之则季节间差异不显著。地表水群落Shannon多样性指数在雨季显著高于旱季(P<0.01)，地下水群落差异不显著；主坐标分析(principle coordinates analysis, PCoA)和置换多元方差分析(P=0.001)表明，不同季节间，地表水和地下水的细菌群落间差异显著。Mantel test相关性分析表明，旱季地下水群落与环境因素的相关性不显著，其余群落均与至少一种环境因素显著相关。中性群落模型(neutral community model, NCM)、修正随机性比率(modified stochasticity ratio, MST)与β最近分类单元指数(β nearest taxon index, βNTI)均表明，地表水群落在雨季受到随机性过程的影响明显高于旱季，地下水存在相似但不明显的趋势；地表水的迁移率在雨季高于旱季，而地下水的变化趋势相反。地表水群落中，季节间抗生素抗性基因(antibiotic resistance genes, ARGs)多样性变化值与MST值负相关(ρ=−0.164,P=4.942e−2)；地下水群落则呈现正相关关系(ρ=0.393,P=1.452e−6)。【结论】 江汉平原人口稠密区地表水和地下水细菌群落的时间动态变化存在差异。地表水和地下水基本性质的差异、雨季频繁的环境扰动，以及地表水、地下水之间的水体交换过程可能是导致上述差异的原因。

Abstract:

[Objective] To reveal the dynamics of bacterial communities in surface water and groundwater in the densely populated area of the Jianghan Plain across seasons and explore the underlying factors causing the temporal variations. [Methods] Water samples were collected from both surface water and groundwater in the densely populated area of the Jianghan Plain, and metagenomic sequencing was employed to investigate the seasonal variations of bacterial communities. The variations in environmental factors, bacterial community structure, and bacterial community assembly processes in the surface water and groundwater were compared considering rainy and dry seasons. [Results] For the surface water, the salinity (P<0.01) and conductivity (P<0.01) during the rainy season were lower than those during the dry season, while no significant seasonal variation was observed in turbidity. For the groundwater, the turbidity was higher in the rainy season than in the dry season (P<0.05), while neither salinity nor conductivity showcased seasonal variations. The Shannon index of bacteria in the surface water in the rainy season was higher than that in the dry season (P<0.01), whereas that in the groundwater presented no significant seasonal difference. The principal coordinates analysis and permutational multivariate analysis of variance (P=0.001) revealed significant seasonal variations in bacterial communities between surface water and groundwater. The Mantel test showed no significant correlations between the bacterial community in the groundwater and environmental factors during the dry season, while other communities were significantly correlated with at least one environmental factor. The neutral community model, modified stochasticity ratio (MST), and β nearest taxon index all indicated that stochastic processes exerted stronger effects on the bacterial community in the surface water during the rainy season than during the dry season, and the trend was similar but not significant for the bacterial community in the groundwater. The migration rate of surface water was higher during the rainy season than during the dry season, whereas that of groundwater showed an opposite trend. (5) The seasonal variations in the diversity of antibiotic resistance genes exhibited a negative correlation with MST (ρ=−0.164, P=4.942E−2) in the surface water, whereas the correlation was positive in the groundwater (ρ=0.393, P=1.452E−6). [Conclusion] The temporal dynamics of bacterial communities in surface water and groundwater in the densely populated area of the Jianghan Plain showed notable differences. These differences can potentially be attributed to distinct basic properties between surface water and groundwater, frequent environmental disturbances during the rainy season, and water exchange processes between surface water and groundwater.