On Circulation, Phosphate‐phosphorus Content, and Zooplankton Volumes in the Upper Part of the Pacific Ocean1

The circulation of the Pacific Ocean may be considered to consist of two high‐latitude cyclonic gyres, two subtropical anticyclonic gyres, and a series of subequatorial zonal flows in alternate directions. The phosphate‐phosphorus at the surface is related to the surface divergence and is high in the cyclones, low in the anticyclones, and high in regions of coastal and equatorial upwelling. The PO 4 ‐P at 100 m is related to the depth of the pycnocline and is also high in the cyclones and low in the anticyclones, and high at the equator and at the poleward edges of the equatorial countercurrents. The zooplankton volume is distributed very much as is the PO 4 ‐P, particularly that at 100 m. It is also low in the anticyclones and high in the cyclones, at the equator and at the poleward edges of the equatorial countercurrents. At the center of the subarctic cyclone, however, zooplankton is only moderate, but PO 4 ‐P concentration is high both at the surface and at 100 m. It is suggested that the surface divergence is too rapid for zooplankton to accumulate in the center of the cyclone, even though reproduction and growth may be prolific. In the California Current zooplankton volume appears to vary inversely with temperature, and an area of minimum volume and maximum temperature is found near the tip of Baja California. It is speculated that this indicates a change from subarctic to subequatorial species. This, and the close relation of the plankton volume to the system of gyres, suggests that the gyres may represent the principal plankton communities.