Diversity and functioning of phytoplankton in the Dubasari water accumulation reservoir [Articol]

Abstract

During the period 2009-2011 the Dubasari lake phytoplankton was represented by a total of 90 species and intra-specific taxons, where Bacillariophyta, Cyanophyta and Chlorophyta species are prevailing. Numbers of phytoplankton ranged from6.16 to 13.76 mln.cel/l with the biomass from 4.27 to 18.41 g/m3 in the spring and from2.13 to 35.99 mln.cel/l with the biomass from 7.02 to 24.13 g/m3 in the summer, and from 3.5 to 13.3 mln.cel/l with the biomass from 2.91 to 17.61 during autumn. Share in the phytoplankton numbers belongs to cianofite algae, and in the algal biomass to bacilariofite algae. The maximum intensity of production processes was recorded in the summer, primary production values being located within 0.84 to 9.95 gO2/m-2 24 h. Seasonal and spatial fluctuations in lake primary production are accompanied by fluctuations in phy- toplankton biomass, community structure of plankton algae succession, changes in nutrient elements concentrations and water transparency values oscillations. There were established variations of the saprobe index values within 1.68 to 2.72. Most saprobe index values were within limits of the β-mezosaprobe zone and indicate attribution to the water the quality classes 3a -”satisfactory pure” – 3b “moderately polluted”.