Home – Home – Jornals – Contemporary Problems of Ecology 2009 number 5

Seasonаl dynamics of Anаbaena flos-aquae (Lyngb.) Breb., including vegetative cells, akinetes and akinete envelopes in bottom sediments and water column in a small Siberian reservoir was studied. It was assumed that even in a rather shallow mixed water reservoir, water bloom with cyanobacteriae starts in the littoral zone and then spreads over the whole water reservoir. Two types of akinetes were observed: in the first half of summer Anаbaenа formed akinetes, which served for vegetative reproduction and germinated in water column soon after differentiation, while in the second half of summer the akinetes served as resting stages, which were deposited to bottom sediments. It was demonstrated that even in the comparatively shallow unstratified reservoir the summer developments of the A. flos-aquae population started in littoral and no rise of akinetes from the sediments of the deeper central station occurred. Thereby, bottom sediments of the profundal parts of reservoirs seem to be a "cemetery" for akinetes of cyanobacteria, which never will germinаte from these sediments. At littoral and open-water stations, abundance and seasonal dynаmics of akinetes in water column and their sinking pattern were very similar. However, seasonаl dynаmics of the abundance of akinetes in sediments in these two reservoir locations differed: whereas the abundance of akinetes in open water increased permanently during the summer, that in the littoral decreased soon after their sedimentation. During winter, the abundance of akinetes in bottom sediments tended to decrease. The reasons of this phenomenon are unknown yet.