Light adaptation of agardhii at different time scales

Abstract

The Markermeer is a eutrophic shallow wind exposed lake. In contrast to other eutrophic lakes in the area, persistent blooms of the cyanobacterium Oscillatoria agardhii do not occur. The severe variations in the available light energy, caused by an excessive resuspension of sediment, are held responsible for this absence. Field experiments were conducted in the Markermeer, to investigate the relations between O. agardhii and the specific light climate in the Markermeer, emphasizing the adaptation rate and extent to light energy level variations. In experiments with traditional light and dark bottles, and bottles moving up and down the water column it was observed that vertical mixing tended to increase the net production of oxygen, as the exposure time near the water surface is too short to cause light inhibition. From experiments with a vertical perspex tube it was concluded that during days with maximum hourly light energy levels above 200 μE·m −2 ·s −1 , the light utilization efficiency was much higher in the morning hours than during the afternoon. This phenomenon did usually not occur at days with lower mean irradiance levels. After prolonged periods of low energy levels (below 50 μe·m −2 ·s −1 ), the light utilization efficiency increases significantly but the maximum production level does not increase.