Ecological Studies On Rotifer And Bacterioplankton Communities In Urban River-lake Interconnected Ecosystems

Urban river-lake interconnected ecosystems different water bodies,form the heterogeneous water environments and provide diverse habitats for improving the zooplankton biodiversity.To understand the effects of connectivity and heterogeneity on the rotifer and bacterioplankton community structure in the river-lake interconnected ecosystems,we conducted the survey quarterly in the two interconnected ecosystems in Changde city(Lake Liuye-the Chuanzi River-the Changde section of the Yuan River,15 sampling sites)and Guangzhou city(Lake Haizhu-the Shiliugang River-the Guangzhou section of the Pearl River,9 sampling sites)during2018-2019,respectively.The main results were summarized as follows:1.Community characteristics of rotifer and bacterioplankton in Changde interconnected ecosystem: A total of 85 rotifer species were recorded and Polyarthra dolichoptera was the first dominant species.The composition of rotifer community in the Chuanzi River was moderately similar to that of Lake Liuye and the Changde section of Yuan River.While the Lake Liuye and the Changde section of Yuan River were moderately dissimilar.The annual average abundance of rotifers was the highest in the Chuanzi River,followed by Lake Liuye,and the lowest in Yuan River.Redundancy analysis indicated that water temperature,nutrients,chlorophyll-a and dissolved oxygen were the key factors to the changes in rotifer community structure.The highest relative abundance of phyla of bacterioplankton in Changde interconnected ecosystem was Proteobacteria,followed by Bacteroidetes,Actinobacteria and Firmicutes.The annual abundance of bacterioplankton decreased in the order: the Chuanzi River > Lake Liuye > the Yuan River,which among the three water bodies were significantly different(p < 0.05).2.Community characteristics of rotifer and bacterioplankton in Guangzhou interconnected ecosystem: A total of 100 rotifer species were recorded and Polyarthra vulgaris was the first dominant species.The species composition of rotifers among the three water bodies were moderately similar.The annual average abundance of rotifers in the Guangzhou section of Pearl River was the highest,followed by Lake Haizhu,and the lowest in Shiliugang River.The biodiversity indices of rotifer community in the Guanghzou section of Pearl River were significantly higher than that in the other two water bodies(p < 0.05).Redundancy analysis revealed that water temperature,chlorophyll-a and total nitrogen were the key factors to the changes in rotifer community structure.On phylum level,the highest relative abundance of bacterioplankton in Guangzhou interconnected ecosystem was Proteobacteria,followed by Bacteroidetes,Actinobacteria,Firmicutes and Cyanobacteria.The annual mean abundance of bacterioplankton decreased in the order: Lake Haizhu > the Shiliugang River > the Pearl River.The annual mean abundance of bacterioplankton,in Lake Haizhu and the Shiliugang River was significantly higher than that in the Pearl River(p < 0.05).3.Relationship between water environment characteristics and rotifers and bacterioplankton in the connected ecosystem in Changde and Guangzhou cities: The trophic status of Changde interconnected ecosystem was mesotrophic and its water quality was better than that in Guangzhou.The trophic status of Guangzhou interconnected ecosystem was middle eutrophic.The species richness,annual average abundance and diversity index of rotifer community in Guangzhou were higher than in Changde.The largest difference of rotifer community structure was found in Changde section of Yuan River and Guangzhou section of Pearl River.Bray-curtis cluster analysis and multidimensional scaling analysis showed a spring-winter and summer-autumn divergence of rotifer community in two interconnected ecosystems.The highest abundance of bacterioplankton in the two interconnected ecosystems both occurred in autumn.Moreover,there were no significant difference between them(p > 0.05).Redundancy analysis indicated that water temperature was the key factor to the variation of bacterioplankton community structure in both interconnected ecosystems.The rotifer abundance was positively correlated with the bacterioplankton abundance in the two connected ecosystems(p < 0.05).Also,P.dolichoptera and bacterioplankton(Bacteroidetes,Firmicutes and ?-Proteobacteria)were positively correlated with the trophic level(p < 0.05).The urban river-lake interconnected ecosystems play important roles in improving the self-purification ability of water bodies and the utilization efficiency of water resource.Rotifer and bacterioplankton are the good indicators of eutrophication.In general,the Guangzhou section of the Pearl River is the most polluted area among the six surveyed water bodies in the two interconnected systems.It is urgent to take measures to protect and manage the water environment in Guangzhou.