PHOTOSYNTHETIC CHARACTERISTICS OF PHYTOPLANKTON IN THE WESTERN BLACK SEA DURING THE AUTUMN BLOOM
Keywords:
phytoplankton, photosynthesis, light, primary production, Black SeaAbstract
In the autumn of 2005 photosynthetic characteristics of phytoplankton were studied along transects from a coast to deep-waters in the western and southern Black Sea. Efficiency of photosynthesis (αB) varied from 0.012 to 0.068 mg C (mg Chl)-1h-1(μE m-2 s-1)-1. Light – saturated rate of chlorophyll a-normalized photosynthesis (P B max ) ranged from 5 mg C (mg Chl)-1 h-1 in the deep-waters to 12 mg C (mg Chl)-1 h-1 in the shelf waters. In the shelf area P B max and αB varied by a factor of 3. Variability of these parameters was as lower as that of the chlorophyll concentration. The mean αB and P B max values at the shelf were higher than those of the deep-water region. The phodoadaptive strategy of phytoplankton was characterized by increasing of αB at lower light levels. During the warm period of year nutrient effect on photosynthetic parameters was critical in their variability. The total integrated primary production (PP) varied from 0.34 to 2.45 gC m-2 day-1. Mean PP values were 1.7 and 0.5 gC m-2 day-1 in the shelf and deep-waters respectively. Strong correlations between PP, P B max , αB and surface chlorophyll concentration have been obtained.
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