The size distribution of phytoplankton and participate organic matter in the Equatorial Atlantic Ocean: importance of ultraseston and consequences

Abstract

The size fractionation of paniculate matter (a , phaeophytin, particulate carbon, nitrogen and phosphorus have been analysed. Primary production by ¹⁴ CO ₂ uptake was also measured with prescreening technique. It appears from this study, that the pariculate matter has a very small size: 40–60% of the chlorophyll passed through 1 μm Nucleopore filter, and 75–90% of the paniculate carbon and nitrogen passed through 3 μm Nucleopore filter in offshore waters. From the atomic ratio C/N, C/P and C/chla, and primary production values, the <3 μm fraction would be mainly constituted by inactive photosynthetic organisms or partides of detritus. The 3–35 μm fraction, in contrast, would be principally active phytoplankton.