Characteristics of the microzooplankton community in Jiaozhou Bay,Qingdao,China

The species composition and abundance of microzooplankton at 10 marine and five coastal stations(Hongdao,Daguhe,Haibohe,Huangdao and Hangxiao) in the Jiaozhou Bay(Qingdao,China) were studied in 2001.The microzooplankton community was found to be dominated by Tintinnopsis beroidea,Tintinnopsis urnula,Tintinnopsis brevicollis and Codonellopsis sp.The average abundance of microzooplankton was highly variable among stations.Specifically,the abundance of microzooplankton was higher at inshore stations and lower in the center of the bay(St.5),bay mouth(St.9) and outside the bay(St.10).The highest average annual densities(346 ind./L) was observed at St.3,while the lowest(55 ind./L) was at St.10.Two abundance peaks were recorded in May(324 ind./L) and February(300 ind./L).The distribution of microzooplankton in three sampling layers at the 10 stations was relatively homogenous and the abundance decreased slightly as the water depth increased.At coastal stations,the highest average annual density was recorded at Hongdao Station(677 ind./L),followed by Daguhe Station(616 ind./L),Haibohe Station(400 ind./L),Huangdao Station(275 ind./L) and Hangxiao Station(73 ind./L).Furthermore,a 24-h sampling analysis conducted at Hangxiao Station revealed that the microzooplankton assemblages were characterized by a bimodal diel vertical migration pattern,with the highest densities occurring at dusk(154 ind./L),followed by dawn(146 ind./L),noon(93 ind./L) and midnight(77 ind./L).The density of microzooplankton in the Jiaozhou Bay was in the middle range of the densities of temperate coastal waters worldwide.