Phytoplankton dynamics and water quality of Prashar Lake, Himachal Pradesh, India

Prashar Lake, an unexplored, high-altitude, shallow, and cold water body located in Himachal Pradesh (India) was studied through monthly surveys in two consecutive years (March 2008 to February 2010). The seasonal variations in chlorophyll a, abundance, and species composition of plankton in relation to hydrography were studied. A total of 67 species belonging to eight groups of phytoplankton were identified. Among 67 phytoplankton species, 19 species exhibited perennial habit. Both plankton and chlorophyll a showed bimodal pattern of fluctuation with peaks in May and September. Annual mean concentrations of chlorophyll a (mg L⁻¹) were recorded as 4.87 in 2008–09, and 4.03 in 2009–10. Palmer pollution index indicated absence of all the 20 pollution tolerant algal species. Pearson correlation revealed a significant relationship between physicochemical parameters and different algal groups. Important physicochemical parameters responsible for distribution of phytoplankton have been studied taking into account the portability of water for irrigation and drinking purposes as per permissible limits of WHO, ICMR, and ISI standards. The values of water quality index were 14.42 during 2008–09 and 16.51 during 2009–10. Based on water quality standards given by Central Pollution Control Board, the water quality at Prashar Lake was between “A and B”. Carlson’s trophic status classified Prashar Lake as oligotrophic with TSI values 17.085 (2008–09) and 14.57 (2009–10). The phytoplankton assemblage, as well as water quality data, suggest that water at Prashar Lake is unpolluted and could be used for various human purposes after disinfection.