Seasonal Pattern of Phototrophic Picoplankton in the Eutrophic Coastal Waters of the Northern Adriatic Sea

Abstract

The abundance and vertical distribution of picophytoplankton were investigated twice a month from March to December 1990, at two stations in the eutrophicated shallow waters of the Northern Adriatic sea. Cyanobacteria and autotrophic eukaryotic cells were enumerated by epifluorescence microscopy. High abundances of picophytoplankton were observed (3.8 × 10 7 cells L −1 , mean value) at both stations. Picophytoplankton cell numbers were highest in late spring-summer (2.3-3.8 × 10 8 cells L −1 ). Cyanobacteria outnumbered eukaryotes on average by nearly an order of magnitude; however, the ratio of eukaryotic picoplankton to cyanobacteria increased in autumn and winter (...)