ANNUAL OCCURRENCE OF MOON JELLYFISH AURELIA sp.1 IN THE JIAOZHOU BAY AND ITS IMPACTS ON ZOOPLANKTON COMMUNITY
胶州湾海月水母(Aurelia sp.1)丰度周年变化及对浮游动物群落的影响

During February—December,2009,monthly investigations were carried out in north-western part of the Jiaozhou Bay.Abundances of the moon jellyfish Aurelia aurita and other zooplankton groups were investigated with vertical net towing.Ecological adaption and impacts on other zooplankton groups of moon jellyfish were analysed,and compared with synchronous zooplankton and environmental data.Ephyra of A.aurita was observed from April to June,when its abundance increased from 0.1 to 2.9ind/m3.Medusa of A.aurita was captured only in July with an average abundance of 1.3ind/m3.The average water temperatures were 11.5℃ at occurrence of ephyra and 20.6 and 25.2℃ during abundance peak of ephyra and medusae,respectively.Total zooplankton abundance(without A.aurita and Noctiluca scintillans) was high from May to July,with the highest of 486.9ind/m3 being observed in May.In July,no significant decrease was observed in total zooplankton abundance,and its geographical variation showed no significant correlation with that of A.aurita.However,through re-analysis of historic data during 2006—2010 in the similar area,it was revealed that annual peak abundances of N.scintillans,copepods and meroplankton were much lower in A.aurita bloom years than in non-bloom years,while no difference was observed in abundances of chaetognaths and small jellyfish.