Effect of climate changing pattern on phytoplankton biomass in Bhimtal lake of Kumaun Himalaya

Climate changes are recognized as important environmental regulatory factors to assess the primary productivity in relation to changing pattern of abiotic and biotic characteristics in lake ecosystem. Bhimtal Lake is the largest lake approximately 85.26 ha among all Kumaun lakes in Uttarakhand. The comparative data of last twenty years of Bhimtal lake catchment basin revealed that air temperature has been increased 1.5 to 2.1 °C in summer, 0.2 to 0.8 °C in winter, relative humidity increased 4-6% in summer and rainfall pattern changed erratically in rainy season. The surface water temperature of lake showed an increasing pattern as 0.8 to 2.6 °C, pH value decreased 0.2 to 0.5 in winter and increased 0.4 to 0.6 in summer and dissolved oxygen level showed a decreasing trend as 0.4 to 0.7 mg/l in winter. The lake ecosystem productivity mainly depends upon the phytoplankton species composition and their biomass as primary producers in the food web cycle. The changing pattern of phytoplankton indicated that biomass of Chlorophyceae and Bacilleriophyceae families were decreasing as 1.99 and 1.08% respectively in Bhimtal lake. The biomass of Cynophyceae was increasing as 0.45% and contributing the algal blooming in summer season. The phytoplankton species composition exhibited their correlationship with pH, water temperature, dissolved oxygen and other nutrient parameters of lake water. The present research paper emphasized on the effects of climatic variables on phytoplankton biomass in Bhimtal lake of Kumaun region. The present research will be contributed significantly to assess the current change status of ecosystem productivity of Bhimtal lake with different time scale.