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湖泊的富营养化问题是全世界面临的主要水环境问题之一[1],富营养化进程加快易引起水华暴发[2-3],透明度下降[4],生物多样性下降[5]等一系列生态系统变化,甚至影响到工农业生产和居民生活,故富营养化问题值得密切关注[6]。关于富营养化现状、发生机制和控制措施等方面,国内外已有一些研究报道[7-10]。中国著名的太湖、巢湖、滇池(简称“三湖”)水华程度分别以“轻度水华”、“轻微水华”、“中度水华”为主[11]。一直以来国家将“三湖”治理纳入国家计划的重点环境治理工程[12]。鄱阳湖整体处于中营养状态,有向富营养化发展的趋势[13]。目前洞庭湖水体富营养化整体程度较轻,但局部水域(大小西湖)富营养化突出,已引起社会各界广泛的关注。有关洞庭湖富营养化研究报道也较多,熊剑等[14-15]利用水质单因子评价和综合营养状态指数对洞庭湖近30年的水质营养状况进行趋势分析,王婷等[16]系统分析了三峡工程运行导致的江湖关系变化对洞庭湖水环境和富营养风险的影响。吴可方等[17]于2016年对东洞庭湖环境因子和浮游植物进行调查,探讨了秋季东洞庭湖蓝藻水华发生的风险水平。然而鲜有在综合营养状态指数评价和洞庭湖浮游植物长期群落演变特征基础上,采用主成分分析对洞庭湖的富营养化影响因素进行研究。
本研究基于1988—2020年对洞庭湖全湖水质和浮游植物的数据跟踪,对洞庭湖的富营养现状及变化趋势作出了全面评价,并结合浮游植物长期的演变特征,采用主成分分析探讨了影响洞庭湖富营养化的主要水质因子,并运用RDA分析揭示了浮游植物与环境因子的关系,以期为洞庭湖水环境保护提供技术支撑。
洞庭湖的富营养演变特征及影响因素
The evolution and influencing factors of eutrophication in Dongting Lake
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摘要: 基于近30年洞庭湖水环境质量调查数据,从综合营养状态指数和浮游植物密度两方面探讨了洞庭湖富营养演变特征,运用主成分分析法筛选主导因子,并进行了环境因子与浮游植物的冗余分析(RDA)。结果表明,2020年洞庭湖全湖综合营养状态指数为49.60,属中营养,近30年,洞庭湖全湖综合营养状态指数在41.09—51.68之间,总体呈上升趋势,表现为东洞庭湖>西洞庭湖>南洞庭湖。自1988年以来,洞庭湖共记录浮游植物8门118属,绿藻门、硅藻门和蓝藻门是洞庭湖的主要物种,洞庭湖呈现出由中营养过渡到轻度富营养的趋势,且蓝藻门上升速度最快。洞庭湖水体富营养化的主导因子是水体中的Chla、TP和TN含量,水位和水流流速也是影响洞庭湖富营养的重要因素。影响洞庭湖浮游植物群落分布格局的主要因素是TN、Chla、pH和DO。Abstract: Based on the investigation of water environmental quality in Dongting Lake in recent 30 years, the characteristics of eutrophication evolution in Dongting Lake were studied from the perspectives of comprehensive nutritional state index and phytoplankton density. The dominant factors were chosen by principal component analysis. The redundancy analyses (RDA) between the environmental factors and the phytoplankton were carried out. The results showed that the comprehensive nutritional state index of Dongting Lake was 49.60 in 2020, which belonged to middle nutrition. In the past 30 years, the comprehensive nutritional state index of Dongting Lake has remained from 41.09 to 51.68, which showed an upward trend, namely East Dongting Lake > West Dongting Lake > South Dongting Lake. Since 1988, a total of 8 phyla and 118 genera of phytoplankton species have been recorded in Dongting Lake. Chlorophyta, diatom and Cyanophyta were the main species in Dongting Lake, and Cyanophyta was growing the fastest. The trend in Dongting Lake was from moderate nutrition to mild nutrition. The dominant factors affecting the eutrophication in Dongting Lake were chlorophyll a (Chla), total phosphorous (TP) and total nitrogen (TN). The water level and flow velocity were also important factors. TN, Chla, pH and Dissolved Oxygen (DO) were the main factors affecting the distribution pattern of phytoplankton community in Dongting Lake.
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表 1 因子载荷量
Table 1. Component matrix
F1 F2 F3 水温 0.336 0.835 0.345 pH 0.401 0.328 0.284 DO 0.695 -0.393 0.509 CODMn 0.987 -0.094 0.020 CODCr 0.991 -0.086 0.018 BOD5 0.828 -0.492 -0.235 NH3-N 0.935 0.297 -0.117 TP 0.861 0.209 0.380 TN -0.196 0.942 0.019 Chla 0.898 -0.056 -0.185 SD -0.279 0.216 -0.833 特征值 5.940 2.287 1.402 方差百分百/% 54.003 20.790 12.749 累积方差百分比 /% 54.003 74.794 87.543 表 2 洞庭湖各环境因子的相关分析
Table 2. Pearson Correlation coefficients of environmental factors in Dongting Lake
水温
TemperaturepH DO CODMn NH3−N TN TP Chla SD ΣTLI pH −0.023 DO −0.246 0.042 CODMn −0.300 0.166 0.319 NH3−N −0.227 0.407* −0.228 0.141 TN 0.029 −0.245 −0.568** −0.517** 0.044 TP −0.19 0.264 −0.032 0.351* 0.578** 0.01 Chla 0.068 −0.435* −0.173 −0.400* −0.449* 0.474** −0.276 SD −0.393* 0.331 0.164 0.3 0.559** −0.05 0.555** −0.350* ΣTLI −0.054 −0.324 −0.330 0.025 −0.107 0.510** 0.263 0.574** −0.066 藻密度 0.002 −0.149 0.107 −0.173 −0.347 0.158 −0.153 0.513** −0.256 0.195 注:**为极显著相关,P<0.01. *为显著相关,P<0.05. Note:**shows a very significant correlation, P<0.01. * shows a significant correlation, . -
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