Investigations on the Photosynthetic Activity of Cyanobacteria of the Baltic Sea Using a Mobile Picosecond-Fluorimeter

Abstract

Pollution and eutrophication of marine waters continue being important environmental problems. High amounts of sulfide and therefore a deficiency of oxygen are found in shallow coastal regions of the Baltic Sea. Some cyanobacteria species can survive under such sulfidic conditions and still introduce oxygen into the sediment and the overlying water thus improving environmental conditions. These organisms are either tolerant of high sulfide concentrations or adapt their photosynthesis by switching from an oxygenic type to an anoxygenic one. Different cyanobacteria were isolated from the island of Hiddensee (southern Baltic Sea) and used for laboratory experiments. Using our recently developed mobile picosecond-fluorimeter [1] we observed variations in the photosynthetic activity of pure cultures of these cyanobacteria due to their response to different sulfide concentrations in the medium. The analysis of the data revealed a correlation of the fluorescence decay to the adaption of the cyanobacteria to sulfide stress and to the production of oxygen. In a first in situ experiment the device was proved at the Zwischenahner Meer (Fig. 1).