p. 7 - 21 COMPARATIVE DATA ON PRIMARY PRODUCTIVITY AND MINERAL PHOSPHORUS UPTAKE IN THE EUPHOTIC ZONE OF THE MEDITERRANEAN AND BLACK SEA A. S. Bologa 1), A. V. Parkhomenko 2), Victoria Smocov 1) 1) Romanian Marine Research Institute Constanta 2) Institute of Biology of Southern Seas, Sevastopol USRR Abstract During May-July 1985 the plancktonic primary productivity of four different sectors of the Mediterranean Sea ranged between 0.5 to 11.3 mg C m-3 day-1 and 0.06 to 0.48 g C m-2 d-1, and in one sector of the Black Sea between 9.4 to 14.7 and 0.78 respectively. Similar phosphate -P concentra- tions in the water column to 90 m were found; the P concen- tration in the euphotic zone (i.e. to 90 m) did not exceed 0.016 g at P 1-1 in the Mediterranean, and 0.013 in the Black Sea. The maximum assimilation rate of P by micro- plankton communities in the Mediterranean occurred at the lower limit of the euphotic zone, but in the Black Sea it was within the euphotic zone at 10 m depth.