Abstract:In order to investigate the community structure characteristics of molluscs in the rock intertidal zone of Zhejiang,field sampling was carried out including eight rocky intertidal sections in Apr.and Oct.2009.A total of 27 species in two seasons were identified,belonging to 3 classes,11 orders,16 families and 22 genera.The molluscs community in the intertidal zone of Zhejiang was mainly composed of subtropical species,including 13 species recorded,and followed by temperature widespread species and temperate species,with 12 species and 2 species,respectively,generally in accordance with the taxonomic features of the East China Sea.The average molluscs biomass and density in spring were 156.15 g/m2 and 83.47 ind./m2,respectively; which were higher than those in autumn,being 88.04 g/m2,63.05 ind./m2,respectively.Dominant species were Thais clavigera,Nerita albicilla,Barbatia obliquata,Nerita yoldii and Septifer bilocularis in spring; T. clavigera,Monodonta labio,B.obliquata,N.albicilla,Septifer virgatus and Chlorostoma rustica in autumn.Dominant species of molluscs varied with different seasons,indicating their functions in the community changed with seasons.The index of Shannon-Winner was from 1.13 to 2.77,the average being 1.85.The index of Pielou's evenness was from 0.33 to 0.77,the average being 0.64.The index of Margalef's species richness was from 0.80 to 2.02,the average being1.27.The community structure of molluscs had been studied by Bray-Curtis similarity clustering and non-metric multidimensional scaling (MDS) analysis.The community could be spatially clustered into three groups during Spring:the first was sections including Nanji Islands and Dongtou,the second was sections including Sanmen,Xiaowushitang,Xiangshan Bay,Ninghai and Xiushan,and the third was Shitang.However,autumn was also clustered into three groups,the first was sections including Sanmen,Xiaowushitang,Xiangshan Bay and Xiushan,the second was sections including Dongtou,Ninghai and Shitang,and the third was Nanji Islands.SIMPER analysis found that the average similarity rate between each section in the group was higher than 37%,and the average difference rate between groups was higher than 66%.