大水面放养凤眼莲对底栖动物群落结构及其生物量的影响

Effects of Large-Area Planting Water Hyacinth on Macro-Benthos Community Structure and Biomass

为研究在太湖竺山湖进行200 hm2的水面放养凤眼莲后对底栖生态环境的影响,进行了连续3个月的底栖生物调查.结果表明,软体动物(主要是铜锈环棱螺)的平均密度从远离到种养区内分别为276.67、371.11和440.00 ind/m2,生物量从远离到种养区内分别为373.15、486.57和672.54 g/m2;表现为种养区内要高于种养区外围;种养区内寡毛类(主要是霍甫水丝蚓)和摇蚊幼虫类的密度和生物量的变化表现为种养区内>远种养区>近种养区.在8～9月间3种底栖动物优势种的密度和生物量都表现为快速增加、但在10月为快速下降的趋势.出现这种情况可能是在9～10月大量蓝藻开始死亡,蓝藻在死亡分解过程中消耗大量溶解氧,并释放出大量的N、P营养盐,提高水体富营养化程度,导致底栖动物死亡.利用Shannon-Weaver和Simpson指数来评价底栖环境,表明水体处于中-重度污染状态.因此,短期内(6个月左右的放养时间)的大水面、高密度的凤眼莲的种植模式尚未表现出对底栖生境及底栖生物的较大影响.

The effects on macro-benthos and benthos environment of planting 200 hm^2 water hyacinth（E.crassipens） in Zhushan Bay,Lake Taihu,were studied during 8-10 months consecutive surveys.Results indicated that average densities of mollusca（the main species were Bellamya aeruginosa） in far-planting,near-planting and planting area were 276.67,371.11 and 440.00 ind /m^2,respectively,and biomass were 373.15,486.57 and 672.54 g /m^2,respectively,showed that average density and biomass of planting area’s were higher than those of others.However,the average density and biomass of Oligochaeta（the main species was Limodrilus hoffmeisteri） and Chironomidae in planting area were lower than that of outside planting area.The density and biomass of three dominant species of benthic animal increased quickly during 8-9 months,decreased quickly in October inside and outside water hyacinth planting area.The reason of this phenomenon could be possible that lots of cyanobacteria cells died and consumed dissolve oxygen in proceed decomposing.Algae cells released lots of phosphorus and nitrogen simultaneously,so macro-benthos died in this environment.The indexes of Shannon-Weaver and Simpson indicated that water environment was in moderate polluted state.On the basis of the survey results,the large-area and high-density planting water hyacinth haven’t demonstrated a great impact on macro-benthos and benthos environment in short planting time（about 6 months planting time）.