CAJ | 학술논문

To understand the effects of the Yellow Sea Cold Bottom Water (YSCBW) on the diel vertical migration (D-VM) of the copepod Calanus sinicus, we surveyed vertical distribution of C. sinicus at a fixed station in the Yellow Sea before (spring) and during (summer) formation of the YSCBW. Cold water (<10?C) was observed in the bottom layer when the water column was thermally stratified in summer, but the water column was thermally well-mixed in spring 2010. Samples were collected from five different layers at 3-h intervals using an opening-closing net. Adult females (1-155 ind./m3) showed a clear normal DVM pattern throughout the entire water column in spring, whereas adult males did not migrate. DVM of copepodite V (CV ) individuals was not clear, but the maximum abundance of CI-CIV occurred consistently in the upper 10-20 m layer, where there was a high concentration of chlorophyll-a (Chl-a ) (0.49-1.19 μg/L). In summer, weak DVM was limited to cold waters beneath the thermocline for adult females (<30 ind./m3), but not for adult males. The maximum abundance of CI-CIV also occurred consistently in the subsurface layer (20-40 m) together with high concentrations of Chl-a (0.81-2.36 μg/L). CV individuals (1-272 ind./m3 ) moved slightly upward noc-turnally to the near-surface layer (10-20 m), where the average temperature was 25.74?C, but they were not found in the surface layer (0-10 m;28.31?C). These results indicate that the existence of the YSBCW affected food availability at depth and the vertical temperature distribution, leading to variation in the amplitude and shape of stage-specific vertical distributions (CI to adults) in C. sinicus before and during the formation of cold waters in the Yellow Sea during the study period.