Spatial heterogeneity and seasonal succession of phytoplankton along the longitudinal gradient in a eutrophic reservoir

Spatial distribution and seasonal succesion of phytoplankton along the longitudinal axis of a eutrophic Římov reservoir (Czech Republic) was investigated from April to October 2007, at 1?2 week intervals. Phytoplankton spatial heterogeneity was the most apparent during the summer reflecting a pronounced gradient of environmental parameters from the river inflow to the dam. The riverine zone differed markedly from downstream parts of the reservoir, being dominated by functional groups D and J (large cryptophytes and colonial diatoms). While a dense cyanobacterial bloom (groups H1 and M) occurred in the transition zone, considerably lower biomass of desmids (Group N) was found at lacustrine zone at the same time. A sudden flood event considerably altered nutrient and light availability, and later even resulted in cyanobacterial dominance in the whole reservoir