Picoplankton and Picophytoplankton in the Ligurian Sea and Straits of Messina (Mediterranean Sea)

Abstract

The vertical distribution of picoplankton and of picophytoplankton in two areas of the Mediterranean Sea was studied by direct counts. Living picoplanktonic cells were counted using nalidixic acid. The epifluorescence technique was used to determine the viable picoplanktonic cells (using DAPI as fluorochrome). Viable picoplanktonic cells were present down to 1200 metres and were more concentrated in the surface layer (3.2×10 8 cell L −1 ) of the Ligurian Sea but more uniformly distributed in the more turbulent waters of the Straits of Messina. Otherwise no consistent correlation of picoplankton numbers with physical or chemical conditions was found