Impact of seasonal variation of water masses on ecological characters of zooplankton in the coastal waters off central Fujian Province

Three oceanographic surveys were conducted in the coastal waters off central Fujian Province(24°55' 25°13'N,119°11' 119°32'E) during December 2009,and April and August 2010.The species composition,eco-groups,dominant species and diversity index of the zooplankton in this area were investigated using the survey data,and impact of seasonal variation of water masses on these ecological characters was discussed.A total of 96 species were identified,including 24 in winter,48 in spring and 72 in summer.From winter to summer,the number of subtropical water species increased gradually and the warm temperate water species decreased gradually.The number of species of offshore species increased gradually and the nearshore species decreased gradually.The dominant species also had obvious seasonal changes.There were three dominant species in winter,three dominant species in spring,and seven dominant species in summer.In winter and spring,dominant species were mainly warm temperate water species,like Calanus sinicus,Paracalanus parvus and Corycaeus affinis.In summer,dominant species were mainly subtropical species,such as Eucalanus subcrassus,Lucifer hanseni and Sagitta ferox.The species diversity of zooplankton was the highest in summer and the lowest in spring.The seasonal changes of these ecological characters were closely related to the seasonal variation of water masses in the Taiwan Strait.The China Coastal Water with low temperature and low salinity and the Strait Warm Current Water with high temperature and high salinity were two main water masses in the Taiwan Strait.The dynamics of these two water masses and their interaction led to the seasonal variations of temperature and salinity of the investigated waters,and further influenced the ecological characters of the zooplankton.