Analysis of the distribution of zooplankton in the Southern Yellow Sea in summer and its influencing factors

Based on the cruise in the Southern Yellow Sea (SYS) including 137 zooplankton sampling stations in the summer,2006,zooplankton species composition,the distribution of zooplankton abundance,biomass,dominant species and indicator species of ecological environment and their influencing factors were studied. Results showed that: species composition was higher than studies in the SYS before; the abundance of Calanus sinicus was the hihghest and exceeded 50% in the total abundance. The biomass was also much higher than previous studies and in this study,the biomass of gelatinous zooplankton was higher than the non-gelatinous zooplankton. The composition of dominant species was similar to studies before. C. sinicus had two high abundance areas,one was in the inside of the Yellow Sea Cold Water Mass (YSCWM) where the Chl a concentration was lower and the other was located in the southern sea area; the occurrence frequency of Aidanosagitta crassa was the highest and its high abundance area occurred from the southern coast of Shandong Peninsula to the east of Haizhou Bay,which was different from that of C. sinicus; Themisto gaudichaudi mainly distributed in the north of the 34°N where was influenced by the YSCWM and the species almost disappeared where the salinity was lower than 31; Euphausia pacifica primarily distributed in the deep water area between 33°-35°N. Euchaeta concinna and Flaccisagitta enflata distributed in the south of 34°N,their distribution pattern might be correlated with the northward current-Changjiang Diluted Water and the Taiwan Warm Current,the northern border of these two species was affected by the southward Subei Coastal Current and the YSCWM. The distribution patterns of the two species can indicate the interactions of the oceanic current mentioned above.