Ecological restoration of a mid-Himalayan lake through biomanipulation and aeration

Abstract

The impact of biomanipulation and aeration activities on trophic structure and water quality of Lake Naukuchiatal was assessed for four years. To restore the ecosystem, manipulation of trophic structure through stocking of fingerlings of golden mahseer, silver carp, Indian major carps, etc. and aeration was done. Water quality parameters (temperature, transparency, pH, dissolved oxygen, nitrate, phosphate, phytoplankton, zooplankton and macrophytes) were analyzed weekly. Wide variations in physico-chemical parameters at initial stage of the work, viz. water temperature (15.3- 24.1 oC), Secchi disc transparency (113- 240 cm), DO (0.1- 11.4 mg L-1), pH (6.9- 8.8), total alkalinity (88- 115 mg L-1), nitrate (0.4- 2.2 mg L-1), phosphate (0.01- 1.53 mg L-1) had stabilized with progression of the restoration activities. Trophic state of the lake had also improved. Mass mortality of fishes that occurred regularly in winter subsided following restoration of the lake in last four years.