Phytoplankton production characteristics and rate of enzyme hydrolysis in the Black Sea in autumn 1992

Primary production in the water column (P_p) and average chlorophyll "a" content in the photo¬synthesis layer (C_chl) varied within the following ranges: 100-370 mg C/m**2 per day and 0.46-0.66 mg/m**3 in central regions of the sea; 320-500 mg C/m**2 per day and 0.58-0.87 mg/m**3 in regions of the continental slope; 570-1200 mg of C/m**2 per day and 2.7-4.9 mg/m**3 in the northwestern shelf. Potential rate of extra¬cellular enzyme hydrolysis of proteins and polysaccharides estimated from total proteolytic and amylolytic enzyme activities (EA) in the photosynthesis layer varied from 210 to 370 e.u./l (enzyme units per liter) in the eutrophic northwestern shelf and from 14 to 100 e.u./l in deepwater mesotrophic regions of the sea. Spatial variability of P_p in the open sea was governed largely by fluctuations of insolation. Autumn rearrangement of the vertical structure of phytocene and simultaneous EA decrease in the uppermost mixed layer started in western parts of the sea and gradually expanded to the east. Analysis of light curves of photosynthesis indicates ability of phytoplankton for rapid light adaptation. Reliable positive correlations between EA and values of P_p, C_chl, and assimilation number are established.