Data_Sheet_1_Study of Heavy Metals and Microbial Communities in Contaminated Sediments Along an Urban Estuary.docx

Estuarine sediments are increasingly contaminated by heavy metals as a result of urbanization and human activities. Continuous multi-heavy metal accumulation in the ecosystem can provoke new effects on top of the complex environmental interactions already present in estuarine ecosystems. It is important to study their integrated influence on imperative microbial communities to reflect on the environmental and ecological risks they may impose. Inductively coupled plasma optical emission spectroscopy analysis for five metals Cd, Cr, Cu, Pb, and Zn showed that Cr and Cu concentrations in intertidal sediments of the urbanized Yangtze River estuary in China have consistently exceeded respective threshold effect concentration (TEC) levels. The geo-accumulation and potential ecological risk index results of the five metals showed that all sampling sites were weakly to moderately polluted, and at considerable to high ecological risk, respectively. Redundancy and correlation analyses showed that Zn followed by Cr in the ecosystem were explanatory of the shifts in recorded microbial community structures. However, the spatial variation in metal concentrations did not correspond to the selection of metal resistance genes (MRGs). Unlike many other dominant bacterial taxa, most of the sulfate-reducing bacteria (SRB) and associated sulfate respiration as the dominant microbially contributed ecological function were found to negatively correlate with Zn and total heavy metal pollution. Zn concentration was proposed to be a potent indicator for heavy metal pollution-associated microbial community compositional shifts under urbanized estuarine conditions. The associations between heavy metals and estuarine microbial communities in this study demonstrate the influence of heavy metals on microbial community structure and adaptations that is often overshadowed by environmental factors (i.e., salinity and nutrients).

随着城市化进程与人类活动的加剧，河口沉积物正日益遭受重金属污染。生态系统中持续累积的多种重金属，会在河口生态系统已有的复杂环境交互作用基础上，引发额外的生态效应。探究重金属对关键微生物群落的综合影响，以反映其可能带来的环境与生态风险，具有重要意义。针对镉（Cd）、铬（Cr）、铜（Cu）、铅（Pb）及锌（Zn）五种重金属的电感耦合等离子体发射光谱法（Inductively coupled plasma optical emission spectroscopy）分析结果显示，中国城市化进程下的长江口潮间带沉积物中的Cr与Cu浓度持续超出各自的阈值效应浓度（TEC）标准。五种重金属的地质累积指数与潜在生态风险指数结果表明，所有采样点均处于轻度至中度污染水平，且分别具有可观至极高的生态风险。冗余分析与相关性分析结果显示，生态系统中的Zn（其次为Cr）可解释观测到的微生物群落结构变化。然而，重金属浓度的空间变异并未与重金属抗性基因（MRGs）的筛选呈现对应性。与多数其他优势细菌类群不同，绝大多数硫酸盐还原菌（SRB）及其主导的硫酸盐呼吸这一主要微生物贡献的生态功能，均与Zn及总重金属污染呈负相关关系。研究提出，在城市化河口环境下，Zn浓度可作为重金属污染相关微生物群落组成变化的有效指示因子。本研究中重金属与河口微生物群落间的关联，揭示了重金属对微生物群落结构及其适应性的影响——这类影响常被盐度、营养盐等环境因素所掩盖。