象山港两种网目网采浮游动物群落比较

分别于2010年3月(春)、7月(夏)、9月(秋)、12月(冬),用浮游生物Ⅰ型(网目505 μm)、Ⅱ型(网目160 μm)网同步在象山港进行6站位2重复的浮游动物取样,比较分析了不同时空下两种网目采集的浮游动物群落差异.结果表明:两网间的浮游动物种类数、丰度、生物量、优势种和群落格局都存在极大差异.其中,Ⅰ网的种类数(61种,包括幼虫)、平均丰度(139.0 ind·m-3)和平均生物量(86.1 mg·m-3)显著低于Ⅱ网(分别为84种、3780.2 ind· m-3和191.1 mg · m-3).在优势种中,除太平洋纺锤水蚤和墨氏胸刺水蚤为两网共有优势种外,其余优势种完全不同.Ⅰ网末检出周年的优势种,而Ⅱ网的周年优势种是针刺拟哲水蚤和桡足类幼体.相似性分析(ANOSIM)和nMDS排序结果显示,两网群落格局不仅在时空上存在显著差异,而且I网群落比Ⅱ网更离散.相似性百分比(SIMPER)分析进一步揭示,两网群落格局间平均非相似性高达75％以上,造成两网群落时空非相似性差异的主要判别种是:针刺拟哲水蚤、桡足类幼体、强额拟哲水蚤和短角长腹剑水蚤,而这些种均为Ⅱ网的优势种.表明象山港浮游动物调查时以Ⅱ网更具代表性.

A comparison of zooplankton communities collected by two types of nets with different mesh sizes in Xiangshan Bay of Zhejiang,East China

In March(spring),July(summer),September(autumn),and December(winter) 2010,the zooplanktons at six stations in Xiangshan Bay were sampled simultaneously by the nets with a mesh size of 505 μm(net type Ⅰ) and of 160 μm(net type Ⅱ),and each sampling had two replicates.The spatiotemporal differences in the zooplanktons communities collected by the two types of nets were compared.There existed great differences in the species number,abundance,biomass,dominant species,and community pattern between the zooplanktons collected by the two types of nets.The species number,average abundance,and average biomass of the zooplanktons collected by net type Ⅰ(61 species including larvae,139.0 ind·m-3,and 86.1 mg·m-3,respectively) were siginificantly lower than those collected by net Ⅱ(84 species,3780.2 ind·m-3,and 191.1 mg·m-3,respectively).In the dominant species,except for Acartia pacifica and Centropages mcmurrichi,the others were completely different between the zooplanktons collected by the two types of nets.In the zooplanktons collected by net type Ⅰ,no species dominating over the year was found,while in the zooplanktons collected by net type Ⅱ,Paracalanus aculeatus and Copepods larva were dominant over the year.The similarity analysis(ANOSIM) and non-metric multi-dimensional scaling(nMDS) ordination revealed that the community pattern of the zooplanktons collected by the two types of nets had significant spatiotemporal difference,and the community pattern of the zooplanktons collected by net type Ⅰ was more discrete than that of the zooplanktons collected by net type Ⅱ.The analysis of similarity percentage(SIMPER) further revealed that the average dissimilarity of the spatiotemporal difference in the community pattern between the zookplanktons collected by the two types of nets exceeded 75%,and the main discriminating species causing this dissimilarity were Paracalanus aculeatus,Copepods larva,Paracalanus crassirostris,and Oithona brevicornis,all of which were the dominant species of the zooplanktons collected by net type Ⅱ.In a word,the zooplanktons collected by net type Ⅱ were more representative for the investigation of the zooplanktons in Xiangshan Bay.