近海沉积物镉-多环芳烃复合污染的微生态效应研究

Cadmium (Cd) and polycyclic aromatic hydrocarbons (PAHs) are typical pollutants in the coastal sediments, and co-existence of them was frequently reported in different levels, thus inducing a serious threat to the benthic ecosystem balance. Therefore, ecological health evaluation standard for typical co-contamination is urgent to be established, which depends on the comprehensive knowledge of its ecological effects. This project intends to collect a series of sediments along a coastal gradient to assemble microcosms, respectively. Cadmium and PAHs will be added to simulate the processes of co-contamination at different levels. The Cd-PAHs interactions on environmental behaviors of each other will be revealed. Meanwhile, the Cd-PAHs interactions on microbial community structure and function will be characterized via multiple angles as microbial biomass and composition, community metabolic diversity, enzyme activity, and functional gene activity, thus uncovering specific patterns of microbial community responding to Cd-PAHs co-contamination. The multivariate correlation and neural network analysis will be applied to illustrate the correlations and interactions among co-contamination, community responses, and environmental factors, thus comprehensively evaluating the microbial ecological effects of Cd-PAHs co-contamination in sediments and the key driving environmental factors, and further screening a series of Cd-PAHs co-contamination indicator taxa and functional indices. This project will provide theoretical basis and technical paradigm on establishing microbial indicators system for ecological health evaluation of typical co-contamination in coastal environment.

镉和多环芳烃是近海沉积物中的典型污染物，且存在不同程度的复合污染状况，对底栖生态系统平衡造成严重威胁。因此，亟需建立典型复合污染的生态健康评价标准，这有赖于对其生态效应的充分了解。本项目拟通过采集近海空间梯度下一系列沉积物分别构建生态微宇宙，对不同水平的镉-多环芳烃复合污染过程进行模拟，揭示镉-多环芳烃交互作用对彼此环境行为的影响规律；同时，通过生物量、群落组成、代谢多样性、酶活和功能基因活性，多角度表征镉-多环芳烃交互作用对微生物群落结构和功能的影响，从而明确群落对镉-多环芳烃复合污染的响应模式。通过多元相关性分析和神经网络构建，分析复合污染物、群落响应和环境因子的关联和相互作用，综合评价近海沉积物镉-多环芳烃复合污染的微生态效应并揭示其环境影响因子，进而筛选一系列对镉-多环芳烃复合污染敏感的种群和功能性指标，为建立近海典型复合污染生态健康评价的微生物指标体系提供理论依据和范例。

为明确污染物共存对近岸海域生态系统的危害，需要从整个生物群落的角度了解复合污染物相互作用的生态效应。本项目聚焦近海沉积物原核生物（细菌和古菌）群落对镉-多环芳烃复合污染的响应，来表征其微生态效应。在完成浙北海域沉积物微生物群落背景调查的基础上，用微宇宙实验研究了沉积物细菌和古菌群落对镉-芘（代表性多环芳烃）复合污染的响应模式。本研究还系统比较了沉积物不同深度下细菌和古菌群落对镉-多环芳烃（菲、芘和苯并[a]芘混合物）复合污染响应模式的差异。研究结果表明：（1）沉积物中芘在8周内未现降解迹象，镉对芘的消减、芘对镉的有效性均无明显影响。（2）镉、芘及其相互作用对沉积物细菌和古菌α-多样性的影响表现出时间性和剂量效应。（3）细菌和古菌群落结构明显呈时间变异性和芘诱导模式，而镉-芘相互作用在7天后持续影响群落结构，改变了群落的演替轨迹。（4）芘污染下（无论镉共存与否）沉积物微生物群落可能处于多环芳烃降解类群的发展阶段，伴随先锋降解类群（来自解环菌属）初露端倪；而镉污染相关类群与镉的相关性均短暂且微弱，这与整体群落组成对镉的抗性相对应。（5）总体上，镉-芘复合污染对细菌和古菌群落功能基因家族组成和氮、磷、硫代谢相关基因（基于PICRUSt预测）无明显影响。（6）镉和三种多环芳烃复合污染对细菌和古菌群落结构的影响在一定范围内会随着沉积物深度的增加而变大。复合污染标志类群的身份在多环芳烃污染和复合污染组间随污染时间和沉积物深度摇摆，反映出镉-多环芳烃相互作用对群落的影响。说明在评估近海复合污染的微生态效应时沉积物深度是重要考量因素。在高通量测序时代，本研究从群落多样性、结构、污染相关类群和功能基因组成多角度地揭示镉-多环芳烃复合的微生态效应，为细致地评估复合污染对近海生态系统的影响提供了基础数据和范例。