The Spatiotemporal Changes Of Zooplankton Community Structure In Xiangshan Bay

Zooplankton sampling was carrid out at six stations in Xiangshan Bay from March (Spring),July (Summer), September (Autumn) to December (Winter)2010, and two replicates of sampleswere synchronously collected by type II (160μm mesh size) net, then spatiotemporal differences incommunity were analysed. The results demonstrated that the number of species were84species(including larvae) in all. Average abundance and average biomass reached3780.2ind/m~3and191.11mg/m~3respecctively.The main dominant species were Paracalanus aculeatus, Paracalanuscrassirostris, Oithona brevicornis, Acartia pacifica, Centropages mcmurrichi and copepodid larvaetc. Moreover, two dominant speices, i.e. Paracalanus aculeatus, Copepods larva, were founded intype II net and dominated throughout the year. Diversity analysis showed, the number ofspecies(25.33)、richness index(4.38) and Shannon-Wiener index(2.55) were all in the summer toget maximum, but evenness index maximum appeared in winter (0.90); Changes in space,evenness index(0.92) and Shannon-Wiener index(2.48) were all higher than the other two regions,middle of the Bay got the most speices. Based on the results of ANOSIM and ordination, thecommunity in II net not only had significantly spatiotemporal differences and community patternare concentrated, but also was more discrete in Autumn and Spring. Clustering analysis results inthe50%level was divided into four groups, spring six stations were divided into two groups, allstations in winter and station1, station2in fall were into the third group, and the rest of the seasonincluding10stations were into the fourth group. Further analyses by SIMPER revealed that theaverage dissimilarity of spatiotemporal differences in II nets exceeded68.87%, and the maindiscriminating species causing spatiotemporal differences in community dissimilarity wereParacalanus aculeatus, Paracalanus crassirostris, Acartia pacifica, Centropages mcmurrichi andCopepods larva.Then, allocating all zooplankton into size classes according to their individual body mass sizeand computing the total biomass per size class, set up2010XiangShan Bay anniversaryzooplankton Sheldon pattern of biomass spectrum and normalized biomass spectrum. Comparingand analyzing the heterogeneity of the spectrum characteristics parameters among different seasons and different regions. The results showed that the individual carbon content of zooplankton rangedfrom0.58ng/ind to23.5ng/ind, can be divided into six grain grade groups. Biomass spectrumwere more for the single-peak type，One-Way ANOVA was used to provide evidence that therewas significant difference in the biomass between summer and the other three seasons, it was also aremarkable difference between mouth region and middle region、bottom region. Anniversary ofnormalized biomass spectrum had the slope and intercept for-1.12and10.90, four seasons’zooplankton spectrum slopes ranged from-1.778to0.577and with the intercepts a range of8.389-11.90,3regions’ normalized biomass spectrum slope range were-2.190--0.478while itsintercepts ranged from8.838-12.41.In addition, this paper also probed into the characteristics of surface layer environmentalfactors and the relationships between environment factors and dominant species abundance、different grain levels of zooplankton abundance.The results demonstrated in different months,water temperature (SWT) was positively associated with chlorophyll-a and was negativelycorrelated dissolved oxygen. At different spaces, the salinity (SAL) decreased significantly frombottom to mouth in Xiangshan Bay, while Chl-a changed reverse. In12dominant species, most ofthe dominant species belonged to the offshore low salt community, and the influence of abundancefrom SWT、Chl-a was most notable, but there was no factor presented significant relationshipwith Oithona fallax. Miniature zooplankton presented significant correlation with SWT、Chl-a.Because that most of small and medium zooplankton belonged to the offshore low salt community,the distribution of abundance in different time and space were mainly influenced by SWT SAL.High abundance contributors of the large zooplankton all belonged to coast groups, its abundancehad a close relation to SWT in time and to SAL in space.