PHYTOPLANKTON RESPONSES TO HYPOLIMNETIC AERATION IN LAKE NAUKUCHIYATAL, CENTRAL HIMALAYA, UTTARAKHANDMamta Pant, Pragya Singh and P.K. Gupta
In this paper we report the results of impact of hypolimnetic aeration on phytoplankton assemblages in a subtropical lake of India. The study was conducted for a period of two years (2017-2018), and the data obtained were compared with those of unaerated time. The aeration in the hypolimnion was done by a high speed aerator. The aeration appeared to change the phytoplankton assemblage significantly. It reduced the number of species and the standing crop of phytoplankton. Most importantly, due to aeration the Cyanophyeae was completely eliminated while the Chlorophyceae and Bacillariophyceae were increased in number. In general, the light weight species of phytoplankton disappeared or reduced in number as a result of aeration. The Shannon-Weiner diversity index as well as concentration of dominance was also found to be reduced. The share of Chlorophyceae and Bacillariophyceae were increased due to reduced pH and release of competition from Cyanophyceae during aeration.