Interannual Comparative Study On The Zooplankton Community Structure In The Adjacent Area Of Yangtze River Estuary In Summer

Marine zooplankton is a group of heterotrophic biotawhich floated in seawater.It's characterized by large quantity and wide distribution in ocean.This research analyzed the community structure,which includes species composition,abundance and dominant species of zooplankton based on the comprehensive survey data at the Yangtze River estuary and adjacent waters in every July from 2014 to 2016.In order to discuss the relevance between zooplankton community structure and environmental factors and its interannual variability,we used an integrated approach which combined of comprehensive multivariate statistical method,CLUSTER analysis,MDS sequence and DCCA rank.Besides it,we discussed the effects of tidal fluctuation on zooplankton community based on the continuous stratified sampling data and tidal data.The main results are as follows:1)A total of 208 macro-mesozooplankton taxas were identified,include 161 species and 47 kinds of larva.The taxas of meso-microzooplankton is 171,whitch included 124 species and 47 kinds of larva.There were 77 species were belongs to both of them(except larva).The copepod was the most species of zooplankton.The distribution of zooplankton in the survey area appeared that more species in off-shore and less in near-shore,and the distribution change and replacement of macro-mesozooplankton species in three years was not significant,but meso-microzooplankton was.2)The average abundance of macro-mesozooplankton in 2014-2016 was 732.53ind/m3,572.63ind/m3 and 818.23ind/m3.The average abundance of macro-mesozooplankton was 2911.82ind/m3,5024.63ind/m3,6597.58ind/m3.The abundance of zooplankton appears that less in off-shore and more in near-shore,but there were part of station had a phenomenon of large increased abundance of zooplankton in some years.The distribution change and replacement of zooplankton abundance in 3 years was not significant.3)There were 6,7 and 9 dominant species of macro-mesozooplankton in 2014-2016.Calanus sinicus was the only dominant species in all the 3 years.The replacement rate of dominant species was 81.8%between 2014 and 2015,and 76.9%between 2015and 2016.The dominate species of meso-microzooplankton were 8,5 and 8.Calanoida larva,Paracalanus parvus and Oithona spp.were the dominant species in both 3 years.The replacement rate of dominant species was 50.0%between 2014 and 2015,and 70.0%between 2015 and 2016.The dominant species of zooplankton had obviously interannual change in 3 years.4)There were no significant differences in biodiversity indices of macro-mesozooplankton in 2014-2016,but there were significant differences in biodiversity indices of meso-micro zooplankton.5)In 2014,the macro-mesozooplankton community could be divided to 3 groups:off-shore group,in-shore group and the mixed group.In 2015,there were 2 groups:off-shore group and in-shore group.In 2016,there were 3 groups:off-shore groups,in-shore groups,and the groups effected by Kuroshio.The meso-microzooplankton community could be divided to off-shore group and the in-shore group both in 2014 and 2015,but the result of the 2016 group division were not significant.6)According to the Pearson rank correlation and DCCA rank,we analyzed the effects of environment factors on zooplankton community distribution and interannual variation.The results show that salinity is the main factor of zooplankton community distribution and interannual variation in Yangtze River estuary,the second factor is temperature,and typhoon and tidal effect were also important factors to the interannual variation of zooplankton community.7)It was proved that there were significant differences between the results of the zooplankton collected by large(I)and medium(II)type of plankton net by the one-way ANOVA analysis.The large type plankton net collected more species but less abundance of zooplankton than medium type plankton net.The abundance of the small body size species in the medium type net was significantly more than that of the large type net.This paper were more completely to reflect the characteristics of zooplankton community through the analysis both of two kinds of net results.8)We analyzed the stratified sampling of the fixed station and the data of the tide in the survey area,the result showed that the fluctuation of the tide had significant effect on the abundance and vertical distribution of the zooplankton.The abundance of zooplankton fluctuated periodically with the fluctuation of the tide,while the tide had no obvious effect on the species change of zooplankton.