Phytoplankton community succession in a lake subjected to artificial circulation

East Sidney Lake, a small, eutrophic bottom release impoundment in NY, has undergone artificial circulation for three seasons. The artificial circulation system resulted in an overall reduction in the physical stability of the water column, making the lake subject to alternating periods of weak chemical stratification and mixing. Phytoplankton community succession exhibited a high degree of regularity from year to year, culminating in mid summer dominance by heterocystous cyanophytes in all years. Changes in the physical structure of the water column, with attendant changes in Z _eu :Z _mix , were not important determinants of phytoplankton community makeup in East Sidney Lake. Seasonal patterns and community characteristics were not affected by artificially induced alterations in stability, but instead were most sensitive to surface temperatures, flushing rate and TN:TP. The timing of cyanophyte blooms was not affected by artificial circulation, nor was maximum seasonal phytoplankton biomass reduced.