Phytoplankton biomass and primary productivity of the south-eastern Mediterranean

The quantitative distribution of chlorophyll a standing crop and primary productivity of the south-eastern Mediterranean waters off the Egyptian coast were studied during four seasons in 1982. The average concentrations of cholorophyll a varied between 73.2 mg.m −2 in winter and 7.1 mg.m −2 in summer, the annual mean being 33.3 mg.m −2. The average rate of carbon fixation varied between 4.82 mg.C.m −2.h −1 in spring and 35.68 mg.C.m −2.h −1 in autumn. The average value of 14C primary productivity integrated for the euphotic zone in the study area amounted to 0.15 g.C.m −2 .h −1. In both the neritic and oceanic waters the nano- and pico-plankton fractions formed the major fraction of both chlorophyll standing crop and primary productivity. Vertical profiles at the offshore stations indicated the presence of a deep chlorophyll maximum at depths 70–150m. The results are discussed and compared with the conditions which prevailed prior to the building of the Aswan High Dam.