BLOOMING OF CYANOBACTERIA IN TURBULENT WATER WITH STEEP LIGHT GRADIENTS - THE EFFECT OF INTERMITTENT LIGHT AND DARK PERIODS ON THE OXYGEN EVOLUTION CAPACITY OF SYNECHOCYSTIS SP PCC-6803

The influence of intermittent high-light dosage on Synechocystis sp. P CC 6803 with respect to oxygen evolution capacity, fluorescence yield and carotenoid pigment pattern was investigated, using high-light- and low-light-adapted cultures. The results showed that this cyanobacteri um was able to survive high light stress for a full day if this stress was applied on and off with intermittently presented recovery periods in darkness. Enhanced respiratory activity in the high-light adapted cells was detected and this may be an important factor in preventing p hotodamage under high light stress. Cyanobacterial photosynthetic and respiratory electron transfer pathways are both present within the sam e membrane, and share common electron carriers. The role of respirator y activity in preventing overexcitation of photosystem 2 is discussed with regard to cyanobacterial ecology.