Changes Of Plankton Community Structure And Its Relationship With Environmental Factors In Zhoushan Coastal Waters

In order to understand the relationship between the changes of plankton community structure and environmental factors in Zhoushan offshore area,according to the results of plankton survey conducted in April,October 2018 and March,April,July and November2019,the GLM model was constructed by using cluster analysis,similarity percentage analysis and canonical correspondence analysis(CCA)methods to analyze the plankton community structure in Zhoushan offshore area.The community structure(group composition,dominant species number)characteristics of zooplankton and fish plankton were analyzed,and the effects of environmental changes on plankton supplement were discussed.The results were as follows:(1)By analyzing the interannual variation of zooplankton community structure in spring and its relationship with environmental factors,according to the cluster analysis of surface temperature and salinity,The results show that the study region is divided into three groups according to cluster analysis of sea surface temperature(SST)and sea surface salinity(SSS): Hangzhou Bay water masses(Area I),upwelling water masses in Zhoushan Island(Area II),and water masses in Zhoushan offshore area(Area III).Water mass groups have significant influence on the composition of zooplankton community.The main species contributing to the difference between the three water masses in spring 2018 and spring 2019(contribution rate >10%)are Calanus sinicus.The contribution species of the same water mass in two years were: Tortanus derjugini(56.91%)and Labidocera euchaeta(12.34%)in Area I,Calanus sinicus(72.64%)and Muggiaea atlantica(13.35%)in Area II,Calanus sinicus(41.93%)and Noctiluca scintillans(22.94%)in Area III.CCA analysis showed that salinity was the main factor affecting the spatial difference of zooplankton community structure in spring,while temperature and chlorophyll a concentration were the main factors affecting the interannual difference of zooplankton community structure in spring.(2)By analyzing the spatiotemporal dynamics of fish plankton in Zhoushan coastal waters and its relationship with environmental factors,it is found that the abundance of fish plankton is the highest at the lower limit of temperature range(13.5～15℃)and the highest at medium salinity(14～17).For the plankton of offshore fish,the abundance is the highest at the upper limit of temperature range(20～23℃)and the highest at the upper limit of salinity range(30～35).Regression analysis showed that the combination of temperature and salinity was an important predictor of fish plankton.The prediction results of GLM model show that:the probability of occurrence of plankton in inshore estuarine fish is 0.65～0.95,the probability of occurrence in offshore is 0.26～0.60;the probability of occurrence in inshore fish is 0.12～0.34,the probability of occurrence in offshore is 0.32～0.54.This study reveals the relationship between the spatial and temporal distribution characteristics of plankton community structure and environmental factors,and provides a scientific basis for the management of spawning ground protection areas and resources quantification offshore of Zhoushan.