宁波东钱湖大型底栖动物群落动态及水质生物学评价

2009年4月—2010年1月,对东钱湖大型底栖动物群落结构及空间分布格局进行了季度调查,并对其环境状况进行生物学评价.共记录底栖动物3门4纲28属30种,其中寡毛类5种、水生昆虫18种、软体动物7种.底栖动物密度、生物量和群落周年次级生产量分别为1 233 m-2、8.0 g/m2(以湿质量计)和35.3 g/(m2.a)(P/B系数法估算),单因素方差分析显示,秋、冬季显著高于春、夏季.东钱湖底栖动物优势种为红裸须摇蚊、长跗摇蚊、菱跗摇蚊和霍甫水丝蚓,红裸须摇蚊为冬季单一优势种.依据底栖动物密度的多维序列分析,可将东钱湖分为4个湖区.基于GIS平台,运用克里格插值法,构建动物参数及BI(Hilsenhoff生物指数)的空间分布格局,显示东钱湖底栖动物群落具有较强的空间异质性:摇蚊幼虫多分布在谷子湖及中部湖区,而软体动物主要聚集在中部偏西南及北部湖区.BI评价结果表明,东钱湖的整体水质为中度污染(BI为7.58),其在时空上有较大差异.其中,2009年4、7、9月为轻度污染(BI为6.66～7.33),2009年11月—2010年1月为中度污染(BI为8.32～8.39);在空间尺度上,中部及北湖偏东部湖区污染较轻,其次为谷子湖及五里塘湖区,南湖偏南部湖区污染较重.

Community Variation of Macrozoobenthos and Bioassessment of Dongqian Lake,Ningbo

Community structure and spatial distribution patterns of macrozoobenthos in Dongqian Lake,Ningbo,were investigated quarterly from April 2009 to January 2010.In total,3 phylum,4 classes,28 genera,and 30 species were identified,including 5 oligochaetes,18 insects and 7 mollusks.The average annual abundance and biomass of the community were 1233 m-2 and 8.0 g/m2(wet weight),respectively.In addition,the annual secondary production was 35.3 g/(m2·a)(wet weight),as calculated by the reported P/B ratios.The dominant species in the lake were three chironomids(Propsilocerus akamusi,Tanytarsus sp.and Clinotanypus sp.) and one oligochaete(Limnodrilus hoffmeisteri).However,the dominant species changed with seasons,with P.akamusi the sole dominant species in winter.Dongqian Lake can be divided into four macrobenthic zones using Multidimensional Scaling(MDS).The GIS database and the Ordinary Kriging technique were employed to construct the spatial distribution patterns of the macrozoobenthic parameters,and to simulate the distribution of the Hilsenhoff biotic index(BI).These patterns showed that the lake was highly spatially heterogenerous,and usually 1-2 zones with high abundance occured across the lake.Chironomids mainly occurred in Guzi Lake and the center of Dongqian Lake;mollusks,however,were concentrated in the northern part of the lake and the southwestern-central part.The results of the bioassessment indicated that the water of the entire lake was moderately polluted(BI = 7.58) with temporal and spatial fluctuations.In spring and summer(April,July and September),the water was light polluted(BI = 6.66-7.33).In contrast,the pollution level in autumn and winter(December and January of the next year) was moderately polluted(BI=8.32-8.39).The water qualities in the central and eastern parts of the north lake were the best,followed by those in the Guzi and Wuli Lakes.The water in the southeastern part of the south lake showed the worst polluted.