沉水植物-附着生物膜体系特征及水流对其调控机理研究

Submersed macrophyte and the bacterial biofilms attached on their surface are important composition of the water purification system and have important role in maintaining the ecological balance and the transformation of polluts in natural water body. Reconstruction of submersed vegetation can increase the biofilm surface, self-purification capacity and the effects of ecological restoration for surface water system in the damaged aquatic ecosystem. Up to date more attentions were paid on aquatic macrophytes in aquatic vegetation recovery processes, however, little is known about both the interaction mechanism between the attached biofilm and their host aquatic plants and the effects of water flow on the structure and function of macrophyte-biofilm system. This project will focus on the response of biofilm and aquatic plants under various conditions. Through field investigation and laboratory experiments, combined with confocal laser scanning, magnetic resonance imaging, environmental scanning electron microscopy, x-ray photoelectron spectroscopy instruments and as well as microbial molecular biological micro-scale technology, we will study the effects of aquatic plants on the distribution, micro-environment and microbial community of biofilm attatched on the surface of aquatic macrophyte and the impacts of biofilm on quatic macrophyte, investigate the impacts of water flow on the plant physiological indexes and on the development,miro-environment, micro-structure and microbial community of surface biofilm, and uncover the effects of water flow on the removal of suspended particles and on the transformation of carbon and nitrogen in macrophyte domain regions. This project will be useful to study the suitable flow condition and water quality for the proper role of submersed macrophytes and the biofilm attached on their surface in a micro-scale level, and thus provide useful theoretical and technical support for the improvement of pollution removal and the ecological restoration efficient at a macro-scale level.

沉水植物及其表面附着生物膜是水体自净体系的重要组成部分,在污染物质转化及维持生态平衡方面起重要作用。恢复沉水植物有利于提高水体生物膜面积、净污能力及生态修复效果。对受损水体沉水植物恢复过程中，当前研究较多地关注植物本身，而对植物-附着生物膜体系特征和水流对其结构与功能的影响机制认识不足。 项目拟通过野外调研和室内模拟实验，借助激光共聚焦、核磁共振、电镜、X射线光电子能谱等仪器和分子生物学分析手段，研究不同水质条件下水生植物对其表面附着生物膜的分布、"微环境"和微生物群落结构及生物膜对沉水植物生理指标的影响,探讨水流对水生植物生理变化及其表面附着生物膜形成、结构、微生物群落组成和"微环境"的影响，阐明水流条件下沉水植物-附着生物膜对水体悬浮颗粒物的去除及碳氮转化效率的影响。从微尺度上探讨沉水植物-表面附着生物膜发挥功能的适宜水流范围和水质条件，为从宏观角度上提高治污效果和生态修复效率服务。

沉水植物是水生态系统的初级生产力，在污染物质转化、提高水体生物多样性以及维持生态平衡方面具有重要作用。沉水植物主要生长在水面以下，容易受到水质、光照、浊度等多方面影响，因而其退化后很难修复。然而，当前工程实践及相关研究较多地关注植物本身，而对沉水植物-附着生物膜体系特征和水流对其结构和功能的影响认识不足。为此，本项目通过现场调研、野外实验及室内模拟研究，进行了以下几个方面研究。1）利用X射线光电子能谱分析、电子显微镜及激光共聚焦技术分析了不同条件下沉水植物表面附着生物膜的微观分布和结构特征，发现植物表面的微生物生物膜通常分布在植物的细胞表面间隙，且通常以小克隆形式存在；水流、水质及植物的生理活性对植物表面微生物植物的分布与有较大的影响。2）从门、纲、目、科和属水平上检了植物表面微生物的主要物种组成及其与外界环境间的关系，发现在低营养水平条件下植物表面微生物的组成有明显的寄主特异性，水质和季节变化对微生物群落有影响；氮增加能够提高部分氮代谢相关基因丰度。3）水流对植物表面微生物群落结构的影响与水流将悬浮颗粒物引入生物膜有关；利用微电极研究发现，水流对植物叶片-生物膜“微环境”有较大的影响。以溶解氧为例，静水条件下溶解氧浓度在水体-植物叶片-生物膜的“微环境”内有明显梯度变化；昼夜变化对该梯度有影响，白天溶解氧浓度高于晚上；动水条件下水体-植物叶片-生物膜“微环境”的溶解氧浓度有显著的差异性。4）水生植物的存在能够改变水流的流态，增加水流的瞬时停留时间、促进悬浮颗粒物的沉降；同位素示踪分析结果显示，水生植物初始阶段对氮的吸收有明显作用，后期氮的转化和去除以植物表面的微生物为主。沉水植物对水流和水质有广泛的适应范围，但植物间具有一定的差异性。这些结果从微观尺度上探讨沉水植物-表面生物膜体系特征及与外界环境的关系，为从宏观角度提高污染治理及生态修复提供了基础。