ON THE TROPICAL PLANKTON COMMUNITIES IN THE WESTERN PACIFIC By

In the region west of 170 ° W long., the wide-spread tropical planktonic animals have three patterns of distribution. The maximum abundance of the species of pattern I is in the equatorial area, the species of pattern II are most abundant in the central areas, and species of pattern III in both equatorial and central areas. The ecological boundaries (i.e., boundaries between areas with maximum abundance of the species of three mentioned patterns) coincide with biogeographical boundaries. In the tropical region west of 170°W long., the major communities are the equatorial and the central ones. They differ from one another in specific composition, in the most numerous species and in some other structural characters. Near the meridian 180 ° in the equatorial community the ratio: phytoplankton biomass/ zooplankton biomass exceeds that in the central communities. In the equatorial area the correlation coefficient between the phyto- and the zooplankton was positive and significant whereas in the central areas it was negative and not significant