Subsurface chlorophyll maximum in August-September 1985 in the CLIMAX area of the North Pacific

Abstract

The deep chlorophyll maximum (DCM) is a widespread feature in the subtropical gyre of the North Pacific. In mid-August 1985, chlorophyll concentration increased in the DCM, then declined over time at 95 to 110 m depth near 28 degree N 155 degree W. During the higher chlorophyll periods the DCM lay within the top of the nitracline. Later, as the chlorophyll concentration declined and the DCM deepened, following the 24.9 sigma-t surface, the maximum was above the nitracline. The DCM was also a maximum in abundance of autotrophic flagellates. Particulate nitrogen was retained over time in the euphotic zone, relative to particulate carbon and chlorophyll. Phytoplankton growth rate at 90 to 110 m depth averaged 0.11 d super(-1) and phytoplankton carbon was about 10 mu g l super(-1), about 50% of the total particulate carbon.