Centre for Research on Environmental Ecology and Fish Nutrient of the Ministry of Agriculture, Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China.
Department of Bioscience, Aarhus University, Silkeborg 8600, Denmark; Sino-Danish Centre for Education and Research (SDC), University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2019 Jun 15;669:711-720. doi: 10.1016/j.scitotenv.2019.03.030. Epub 2019 Mar 8.
Benthic diatoms are useful indicators of the ecological state of river systems. To understand the factors determining benthic diatom metacommunity composition in urban rivers, we studied in situ surface sediment diatom communities from 23 rivers in Shanghai City. Based on our study results on the metacommunity structure of benthic diatoms and hierarchical cluster analysis (HCA), we found substantial differences between restored (G1) and unrestored rivers (G2-G4) in taxa richness, relative abundances, and dominant and indicator taxa of benthic diatoms. The epiphytic diatoms Cocconeis placentula and Amphora libyca var. baltica were representative of the restored rivers (G1), where aquatic macrophytes were more abundant and the water was clearer. The motile epipelic diatoms Navicula recens and Navicula germainii dominated the moderately polluted rivers (G2). The eutrophic taxa Cyclotella meneghiniana, Aulacoseira granulata, and Cyclostephanos tholiformis dominated in G3, which comprised relatively heavily polluted rivers with low organic matter sediment and high disturbance. The polysaprobic taxon Nitzschia palea and the halophilous taxon Fallacia pygmaea represented relatively heavily polluted rivers with a comparatively higher sedimentary salinity (SSal) (G4). Redundancy analysis (RDA) revealed that total phosphorus (TP), dissolved organic carbon (DOC), silicon dioxide (SiO), dissolved oxygen (DO), Secchi depth (SD), SSal, and the ratio of carbon to nitrogen (C/N) in the sediment were important environmental factors explaining variation among benthic diatom metacommunity composition. Partial RDA (pRDA) implied that the relative importance of environmental factors in structuring benthic diatom metacommunity was much higher than spatial factors. Classification and regression trees (CART) further indicated that DOC, the sediment C/N ratio, and SSal were the key local environmental factors affecting grouping patterns of benthic diatom metacommunities. Our study proposes that benthic diatom metacommunities respond to the complex characteristics of local environment in urban rivers and provides useful knowledge for consideration in the ecological monitoring of urban river systems.
底栖硅藻是河流生态系统的重要指示生物。为了了解城市河流底栖硅藻后生群落组成的决定因素，我们对上海市 23 条河流的原位表层沉积物硅藻群落进行了研究。基于我们对底栖硅藻后生群落结构的研究结果和层次聚类分析（HCA），我们发现恢复区（G1）和未恢复区（G2-G4）的底栖硅藻在分类丰富度、相对丰度、优势和指示种方面存在显著差异。附生硅藻 Cocconeis placentula 和 Amphora libyca var. baltica 是恢复区（G1）的代表性物种，那里水生植物更为丰富，水质更为清澈。运动性附生硅藻 Navicula recens 和 Navicula germainii 则占据了中度污染的河流（G2）。富营养化类群 Cyclotella meneghiniana、Aulacoseira granulata 和 Cyclostephanos tholiformis 在 G3 中占主导地位，G3 包含相对污染严重、有机质含量低、扰动大的河流。多污性分类群 Nitzschia palea 和嗜盐性分类群 Fallacia pygmaea 则代表了相对污染严重、沉积盐度（SSal）相对较高的河流（G4）。冗余分析（RDA）表明，总磷（TP）、溶解有机碳（DOC）、二氧化硅（SiO）、溶解氧（DO）、透明度（SD）、SSal 和沉积物中的碳氮比（C/N）是解释底栖硅藻后生群落组成变化的重要环境因素。偏冗余分析（pRDA）表明，环境因素在构建底栖硅藻后生群落结构中的相对重要性远高于空间因素。分类与回归树（CART）进一步表明，DOC、沉积物 C/N 比和 SSal 是影响底栖硅藻后生群落分组模式的关键局部环境因素。本研究表明，底栖硅藻后生群落对城市河流复杂的局部环境特征有响应，为城市河流生态系统的生态监测提供了有用的知识。
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