Abundance and Biomass of Phytoplankton and Chlorophyll Concentration in Eastern Mediterranean in Late Summer Period

Abstract

Abstract. The data on taxonomic composItIOn, abundance, and biomass of phytoplankton and chlorophyll a concentration in the eastern part of the Mediterranean Sea during late summer period are given in the paper. Different methods of measurements of the chlorophyll a concentration are compared. All the quantitative characteristics of phytoplankton manifest the oligotrophic level of water productivity during the period under study. The spatial distribution of the abundance and biomass of phytoplankton and chlorophyll a concentration are significantly influenced by the mesoscale eddies of typical size 10-50 miles. The quantitative characteristics of phytoplankton in the coastal zone were usually higher, as compared with the open sea regions. As for vertical distribution of micro-and nanophytoplankton, the maximum cell concentrations occurred within the upper homogenous layer and in the layer of pycnocline. The vertical profiles of phytoplankton and chlorophyll a were compared with the profiles of fluorescence; the maximum of fluorescence corresponded to the maximum of chlorophyll a concentration and seemed to result from high concentration of picophytoplankton. The maximum of fluorescence also manifested itself in the cases when the cell densities in the layers of maximum if micro-and nanophytoplankton exceeded 10 4 cells per liter.