[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 microm (net type I) and of 160 microm (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 x m(-3), and 86.1 mg x m(-3), respectively) were siginificantly lower than those collected by net II (84 species, 3780.2 ind x m(-3) and 191.1 mg x 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.