太湖软体动物现存量及空间分布格局(2006-2007年)

Standing crop and spatial distributional pattern of Mollusca in Lake Taihu, 2006-2007

2006年11月至2007年10月对太湖软体动物进行了一周年调查.软体动物在30个采样点的出现率为90.0%,采集的232份样品中共记录到9科12属12种.软体动物在分布区的年均密度和生物量分别为266ind./m2、102.2g/m2.河蚬(Corbicula fluminea)和铜锈环棱螺(Bellamya aeruginosa)是太湖软体动物的优势种,河蚬的出现率为90.0%,年均密度和生物量分别为174ind./m2、58.3g/m2,其主要分布在西南湖区(393-896ind./m2)和贡湖湾(393-552ind./m2);铜锈环棱螺的出现率为56.7%,年均密度和生物量分别为58ind./m2、61.6g/m2,主要分布在东太湖(140-299ind./m2).主成分分析结果表明,河蚬空间分布格局取决于生境类型和底质性质,而螺类的分布与水生植物的分布相一致,说明水生植物对螺类的分布有重要影响,这与经典的螺-草互惠理论相一致.比较1987-2006年太湖软体动物群落结构变化发现,20年来河蚬的高值区域已由梅梁湾、竺山湾转变为大太湖,河蚬个体大小趋于小型化发展(P<0.001),而环棱螺小型化趋势并不显著(P=0.051).

An annual investigation of Mollusca was carried out in Lake Taihu between November 2006 and October 2007. Altogether 12 species were recorded, belonging to 12 genera of 9 families in 232 samples. The occurrence frequency of benthic Mollusca was 90.0% in 30 sampling sites. The annual average density and biomass of Mollusca in its distribution area were 266ind./m^2, 102.2g/m^2, respectively. Corbiculafluminea and Bellamya aeruginosa were the dominant species of Mollusca in Lake Tathu. The occurrence frequency of C. fluminea was 90.0%, and the annual average density and biomass were 174ind./m^2, 58.3g/m^2, respectively, which mainly distributed in the southwest part of Lake Taihu（393-896ind./m^2） and Gonghu Bay （393-552ind./m^2）; the occurrence frequency of B. aeruginosa was 56.7%, and the annual average density and biomass were 58ind./m^2, 61.6g/m^2, respectively, which mainly distributed in the east part of Lake Taihu. Principal Components Analysis showed that habitat types and characteristics of sediment were the key factors determined the spatial distribution pattern of C.fluminea, while that of the gastropods was mainly influenced by the distribution of macrophytes, which coincided with the ＂mutualistic theory＂. Analyzing the variation of Mollusca community structure between 1987 and 2006, the results showed that the mainly distributed area of C.fluminea has changed from Meiliang Bay and Zhushan Bay to the central and southwest part of Lake Taihu, and the size of C. fluminea showed a tendency of decrease （P〈0.001）, while the average weight of B. aeruginosa did not changed remarkably （P=0.051）.