TRANSPORT OF THE NEMOPILEMA NOMURAI IN THE YELLOW SEA AND EAST CHINA SEA REVEALED BY FIELD OBSERVATION, SATELLITE DATA, AND PARTICLE-TRACKING EXPERIMENTS

摘要

The spatial distribution of the giant jellyfish Nemopilema nomurai and its relation to water masses and circulation in the Yellow Sea and East China Sea were investigated by ship observations, satellite sea surface temperature (SST), and particletracking experiments. Temperature and salinity were examined by hierarchical clustering, and eight main water masses were identified. High abundances of giant jellyfish were observed in Southern Yellow Sea Water and in mixed waters, but few jellyfish were observed in other water masses. Variation in satellite SST was used to characterize the seasonal variation in the water masses. The results indicated that as the winter monsoon weakened, a water mass with SST (>15qC) at the Jiangsu coast in May extended northeastward and eastward until July. Southerly wind was probably an important factor inducing this northeastward circulation. Moreover, transport of jellyfish was verified by backward, forward particle-tracking experiments based on the flow field from a numerical model and an independent ferry data. The water masses with jellyfish traced back to the Jiangsu coast in the month of May. Furthermore, water masses without jellyfish traced back to the mouth of the Changjiang River, and the Taiwan Strait. These results indicate that the high abundance of giant jellyfish observed in July came from the northern East China Sea or southern Yellow Sea coast in May when ephyrae were liberated from polyps there as SST increased from below 15qC to higher values.