DIVERSITY OF CHLOROPHYCEAE IN THE MIRIK LAKE OF THE DARJEELING HIMALAYAN REGION

“Mirik Lake” is an artificial reservoir of Mirik town of the Darjeeling Himalayan region of West Bengal, India at an altitude of 1767 meters above mean sea level. This Lake was constructed in 1979 primarily for the facilitation of commercial tourism in Darjeeling and is fed by both perennial streams and rain water. The Lake is not only used for different recreational activities but also supplies drinking water to the local people of the Mirik Town. The Chlorophyceae constitute a large and diverse group of fresh water algae including members that are important ecologically and scientifically. Chlorophyceae are the photosynthetic organisms and one of the pioneer species in aquatic food web. Diversity of Chlorophyceae was studied in the Mirik Lake of Darjeeling Himalayan region for a period of two years at monthly basis from the surface water samples of seven selected sampling locations. A total of twenty five varieties of Chlorophyceae were recorded during the whole study period, of which Ankistrodesmus sp., Cosmarium sp., Chlorella sp. and Chlorococcum sp. were the most common species found throughout the year. Some pollution tolerant genera of Chlorophyceae were also observed during the investigation period among which Chlamydomonas sp., Scenedesmus sp. and Chlorella sp. were the most common indicator of anthropogenic pollution of the lake. The density of Chlorophyceae varied from 445 to 4596/ml and the highest diversity was recorded at sampling location 3 and 4. Highest density was observed at Site 3 and lowest density and diversity recorded in case of Site 2 might be due to greater anthropogenic activities of the site.