Distribution of the prochlorophyte Prochlorococcus in the central Pacific Ocean as measured by HPLC

Abstract

The abundance of the prochlorophyte Prochlorococcus along a 56°-long meridional (175°E) transect in the central Pacific was measured by determining divinyl chlorophyll a (divinyl Chl a) during August and September 1993. The aims of this study were to investigate the large-scale spatial distribution patterns of Prochlorococcus, to evaluate its contribution to total phytoplankton biomass, and to identify the environmental boundaries of its distribution in the central Pacific Ocean. Prochlorococcus was detected at depths below the euphotic zone (<250 m) at stations south of 40°N by the presence of divinyl Chl a. For most of the subtropical and tropical central Pacific, Prochlorococcus accounted for >50% of the total Chl a (divinyl Chl a + Chl a) above the 1% isolume and generally occurred between 15–30°C and 0–10 µM nitrate plus nitrite.