Variation Of Zooplankton Community In Chinese Estuaries Along Latitudinal Gradient During Spring

The zooplankton samples from stations was investigated in Guanhe Estuary,Changjiang Estuary(Yangtze River),Oujiang Estuary,Jiulongjiang Estuary and Beilun Estuary,(covering 14 latitudes)during April or May of 2010 to 2012.The difference of abundance,dominant species,diversity index(H'),replacement rate(R)and similarity coefficient(S)were compared.From north to south,the Species composition and ecological characteristics of the zooplankton community was studied along latitudes in spring.In different estuaries,the reasons of zooplankton community variation was explained based on the temperature and water mass along t he coastal waters.This paper clearly illustrated the shifty tendency of zooplankton community and provided basic data for the research in estuarine zooplankton ecology.The specific research results were as follows:According to the adaptability temperature,the zooplankton was divided two ecological characteristic: warm-temperate species and subtropical species,in five estuaries along latitudinal Gradient.From north to south,the ratio of warm-temperate species was gradually decrease,83.33%?48.39%?45.00%?43.75% and 30.43%,respectively;The ratio of subtropical species was gradually increase,16.67%?51.61%?55.00%?56.25% and 69.57%,respectively.The warm-temperate species predominated over the total abundance in Guanhe estuary(96.16%),C hangjiang estuary(95.57%),Oujiang estuary(97.83%),Jiulongjiang estuary(95.53%).Contrarily,in Beilun estuary,the abundance of subtropical species have remarkably higher ratio(82.39%)and the ratio of warm-temperate species abundance was only 17.61%.The dominant species was all warm-temperate species in Guanhe estuary,Changjiang estuary,O ujiang estuary and Jiulongjiang estuary.Dolioletta gegenbauri,subtropical species,was alone dominant species in Beilun Estuary.Calanus sinicus,warm-temperate species,was dominant species in every Estuary.The five estuarine zooplankton can be divided into three zooplankton group which were the no rthern warm temperate group,southern subtropical group and estuarine brackish-water group.The northern warm temperate zooplankton group included Guanhe Estuary,Changjiang Estuary(Yangtze River),Oujiang Estuary and Jiulongjiang Estuary,the warm temperate species was the mainly.In the southern subtropical zooplankton group,only constituted by Beilun Estuary,the subtropical species was dominated.The part stations of Changjiang Estuary formed estuarine brackish-water group.The zooplankton species of the five estuaries were divided into three different zooplankton fauna,which were the northern temperate,central tra nsitional and southern subtropical from the south to the North.At high latitude,only the Guanhe Estuary belongs to the northern temperate,the warm-temperate species was dominated,which had a lower diversity index(H')(1.19)and located in the temperate sea.The replacement rate(R)and similarity coefficient(S)of Guanhe Estuary were significantly different from the other estuaries.In central transitional zooplankton fauna,constituted by O ujiang Estuary and Changjiang Estuary,it was exclusively of the subtropical species and warm temperate species,which had an alike diversity index(H')(1.31 and 1.86,respectively),situated in the transition waters between subtropical and temperate.Between the two estuaries,the replacement rate(R)were lowest(58.33%)and the similarity coefficient(S)were highest(58.82%).The southern subtropical zooplankton fauna included Beilun Estuary and Jiulong Estuary.In this fauna,the subtropical species was the mainly and a different diversity index(H')(1.01 and 2.18)were recorded,located in the subtropical sea.There placement rate(R)and similarity coefficient(S)were respectively 65.52% and 51.28% between Beilun Estuary and Jiulong Estuary.From south to north,along with the increase of latitude,the structure of estuarine zooplankton community has changed significantly.Linear regression figured that replacement rate(R)was positively correlated with the difference of longitude between the two estuaries in Chinese((35)N),R=0.026(35)N+0.608(p=0.002).Similarity coefficient(S)was negatively correlated with the difference of longitude((35)N),S=-0.034(35)N+0.578(p=0.001).In spring,the coastal waters of the Yellow Sea and East C hina Sea was the warm temperate climate;the subtropical climate was the main feature in the Northern South China Sea.With latitudinal decreasing,the water temperature was gradually increased in C hinas coastal area of from north to south.Additionally,the southward coastal currents and water masses of offshore have significant influence on the estua rine waters.Therefore,these factors became the main reasons that formed the distinct tendency of estuarine zooplankton communities from north to south.