Abstract: As one of the most important marine groups, zooplankton are very sensitive to climate change and anthropogenic activities. In this study, the structures and variations of zooplankton community were considered on the basis of monitoring data in Bohai Bay in the summer from 2004 to 2015, and the relationship between the zooplankton and environmental variables was examined. Results showed that species number and biodiversity indices of zooplankton appeared an increasing trend in Bohai Bay. Among 7 phyla identified, two major groups of Arthropoda and Coelenterata showed an increasing abundance in recent years. As a result, the zooplankton composition in the Bohai Bay had changed dramatically during 12 years: the number of large-sized copepods such as Calanus sinicus and Labidocera euchaeta had decreased gradually, while small copepods such as Acartia pacifica and Centropages dorsispinatus as well as gelatinous zooplankton such as Oikopleura dioica and Eirene ceylonensis had expanded. It was revealed that the zooplankton community variation mainly related with the environmental variables such as changes in temperature, salinity and nutrients concentration in Bohai Bay.

Key words: Bohai Bay, zooplankton, community variation, environmental variables