On the Distribution of Plankton Collected along the Meridian 130°E

14 Stations along the meridian 130° E between 5° N and 30° N were occupied by the training ship Keiten-maru during her cruise of the NORPAC EXPEDITION in July 1955. Plankton samples were collected by vertical (0-50 m) haulings of a net of No. 13 bolting silk. Volume of plankton was measured by the settling method and number of organisms was counted. As shown in table, the settling volume of plankton was largest at the St. Ke 546 (12.5 cc) near Kyashil, and smallest at St. Ke 543 (2.0 cc) near Rasa Is. The number of zooplankton organisms varied between 230/m3 (St. Ke 543) and 2,500/m3 (St. Ke 549), dinoflagellates between 30/m3 (St. Ke 549) and 1,300/m" (St. Ke 540), and phytoplankton between 1,300/m3 (St. Ke 547) and 15,000/m3 (St. Ke 548). As is indicated in table, the following groups of organisms are the important constituent. Zooplankton : Copepoda, Appendicularia, Protozoa, Chaetognatha Dinoflagellata : Ceratium, Dinophysis, Ornithocercus Phytoplankton : Rhizosolenia, Chaetoceros, Trichodesmium and some others (Coscinodiscus, Thalassiothrix, Climacodium etc.