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We characterized variations in bacterioplankton community composition(BCC) in mesocosms subject to three different treatments. Two groups contained fish(group one: Cyprinus carpio; group two: Hypophthalmichthys molitrix); and group three, the untreated mesocosm, was the control. Samples were taken seven times over a 49-d period, and BCC was analyzed by PCR-denaturing gradient gel electrophoresis(DGGE) and real-time quantitative PCR(q PCR). Results revealed that introduction of C. carpio and H. molitrix had a remarkable impact on the composition of bacterioplankton communities, and the BCC was significantly diff erent between each treatment. Sequencing of DGGE bands revealed that the bacterioplankton community in the different treatment groups was consistent at a taxonomic level, but differed in its abundance. H. molitrix promoted the richness of Alphaproteobacteria and Actinobacteria, while more bands affiliated to Cyanobacteria were detected in C. carpio mesocosms. The redundancy analysis(RDA) result demonstrated that the BCC was closely related to the bottom-up(total phosphorus, chlorophyll a, phytoplankton biomass) and top-down forces(biomass of copepods and cladocera) in C. carpio and control mesocosms, respectively. We found no evidence for top-down regulation of BCC by zooplankton in H. molitrix mesocosms, while grazing by protozoa(heterotrophic nanoflagellates, ciliates) became the major way to regulate BCC. Total bacterioplankton abundances were significantly higher in C. carpio mesocosms because of high nutrient concentration and suspended solids. Our study provided insights into the relationship between fish and bacterioplankton at species level, leading to a deep understanding of the function of the microbial loop and the aquatic ecosystem. 相似文献
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大通湖是湖南省面积最大的淡水养殖湖泊,冬季作为捕鱼的旺季并且水位较低,水体和表面沉积物中氮、磷容易受到渔业生产的影响。本文从地统计学出发,通过研究冬季大通湖水体和沉积物中有机质(OM)、氮(N)和磷(P)的空间结构特征及其耦合关系,探讨大通湖富营养化程度及其影响因素,为可持续水产养殖和生态修复提供科学依据。结果表明:冬季大通湖水体中总氮(TN)、总磷(TP)浓度较高,平均值分别达到了3.78mg/L和0.29mg/L,为劣Ⅴ类。水体中NH_4~+含量相对较低,平均为0.17mg/L,属于地表水Ⅱ类。与2011年数据比较,沉积物中TP浓度较高,平均升高到了1469mg/kg;而沉积物TN基本持平,平均为1224mg/kg;沉积物TP和水NO_3~-的"块金值/基台值"分别为43.4%和34.5%,表现为中等空间相关性(spatial dependence),其他N、P指标的"块金值/基台值"均低于25%,表现为强烈空间相关性。冬季大通湖沉积物OM、TN和TP在空间上呈现出有规律的带状分布,而水体N、P大体上呈现出"品"字形的斑块分布;水体中的氮磷比平均为13.03,比较适合浮游植物生长;沉积物OM只与沉积物TN和TP呈极显著正相关(P0.01),而积物中TN和TP与水体中的TN和TP相关性不显著。因此,大通湖水体修复在控制外源输入的情况下,还应考虑综合的生态系统工程措施。 相似文献
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