洞庭湖底栖动物长期演变特征及影响因素分析

为揭示洞庭湖底栖动物种群长期变化趋势及环境影响,利用20多年的监测数据分析洞庭湖底栖动物种群组成、优势种、多样性指数变化动态,并应用典范对应分析(RDA)研究了底栖动物种群结构与环境因子的影响。结果表明:1991-2012年洞庭湖底栖动物多年平均种数53种,以水生昆虫(占41.5%)、软体类(占39.6%)为主。全时段水生昆虫种数、密度整体呈缓慢下降趋势;软体动物密度基本平稳,种数整体呈缓慢上升趋势。2010年以后优势种由水生昆虫、软体类与钩虾等为主的清洁型种类向以寡毛类、软体类等为主的清洁型与耐污型种类转变。东洞庭湖底栖动物种数、密度与多样性指数均低于西、南洞庭湖。RDA分析结果显示洞庭湖水体总磷、叶绿素a和透明度是影响底栖动物种群的主要水环境因素。三峡工程运行后入湖水沙减少、水位变化对底栖动物种群有一定的负面影响。

Long-term evolution and influencing factors of macrozoobenthos in Dongting Lake

In this study, the recent 20 year monitoring data were collected to analyze the variations of population composition, dominant species and biodiversity index of macrozoobenthos in Dongting Lake. The RDA method was also employed to examine the relationships between macrozoobenthos and environmental factors. Results showed that(1)the average richness of macrozoobenthos was 53 species in 22 years, and the main species were aquatic insects(41.5%) and mollusk(39.6%).(2)Species number and density of aquatic insects overall showed a slowly declining trend, while the density of mollusks basically kept stable, and species of mollusks showed a slowly increasing trend.(3)After 2010, the dominant species shifted from clean water typed aquatic insect, mollusk and gammarid to clean water typed and pollution-tolerant oligochaetes and mollusk.(4)The macrozoobenthos species, density and biodiversity in Eastern Dongting Lake were lower than those in Western and Southern Dongting Lake.(5)TP, chl-a and transparency were main factors influencing the population composition of macrozoobenthos in Dongting Lake. The loss of water and sediment influx from upstream rivers and the variation of water level resulted from operation of the Three Gorges Project had negative effects on the population composition of macrozoobenthos.