Physical processes influencing the occurrence of the giant jellyfish Nemopilema nomurai (Scyphozoa: Rhizostomeae) around Jeju Island, Korea

The physical and biological processes affecting the spatialdistribution of the giant jellyfish Nemopilema nomurai wereinvestigated in the northern East China Sea and southern YellowSea in July 2006, when large abundances of this jellyfish occurredin Korean waters. Well-characterized water masses were detectedduring the study period. These were the Tsushima Current water,Yellow Sea Bottom Cold Water and Changjiang Diluted Water (CDW).The spatial distribution of Chl a concentrations estimated byocean colour imagery showed that the CDW flows to the northeast.The CDW was accompanied by high abundances of small and medium-sizedzooplankton (0.2–0.5 mm and 0.5–1.0 mm, respectively)and N. nomurai, in comparison with the other water masses. Large(1.0–2.0 mm) and macro-sized zooplankton (2.0–5.0mm) did not show a relationship with the CDW. The distributionof N. nomurai was very restricted and intimately related withthe CDW. In fact, large abundances only occurred in the westernboundary region of the CDW. The results were supported by Pearson’scorrelation analysis, which showed a positive relationship betweenthe CDW, small- and medium-sized zooplankton and the giant jellyfish.We conclude that the CDW had entrained N. nomurai into the watersoff the southwest coast of the Korean peninsula and it was thentransported into the Yellow and East/Japan seas.