The seasonal abundance, vertical distribution, and relative microbial biomass of chroococcoid cyanobacteria at a station in southern California coastal waters

Abstract

The standing stock of autofluorescent chroococcoid cyanobacteria (1 μm in diameter) paralleled the seasonal trends of phytoplankton and bacterioplankton at a station in southern California coastal waters. Low winter levels increased through the summer to peak levels in the early fall. The greatest number of autofluorescent cells was found within the top 30 m of the photic zone(0.1 × 10⁷ to 7 × 10⁷ cells∙L⁻¹). Numerically, autofluorescent cells accounted for 3% of the total population of prokaryotes, while accounting for 20% of the total prokaryotic biomass. With respect to the total microbial (0.2–203 μm) biomass, the bacterioplankton averaged 5%; autofluorescent cells averaged 1%, with phytoplankton accounting for the remaining 94%.