Phytoplankton diversity in relation to physico- chemical environmental variables of Nachiketa Tal, Garhwal Himalaya Submit Manuscript | http://medcraveonline.com Introduction Lakes are the important natural resources present on the Earth. These are the type of productive ecosystem important for any geographical region, as they play signifcant role in its ecological stability. 1 The Nachiketa Tal is an important lake of Garhwal Himalaya. This lake is surrounded by dense forest of Querecus, Abies, Rhododendron and Myrica, etc. and receives its water from the watershed. The variations and distribution of phytoplankton in freshwater lake depend on its physiochemical features. 2 Phytoplanktons are the primary producer and play a vital role in food chain of aquatic ecosystem. 3,4 Due to this reason, phytoplanktons are usually used as an ecological indicator to assess the ecological health and the stress effects of chemical contaminants on aquatic ecosystems and they are also necessary to sustain a healthy aquatic ecosystem. 5‒8 Dynamics in the phytoplankton biomass are the result of the complex interaction of physical, chemical and biological processes. The availability of nutrients infuences the diversity of the phytoplankton. From the past few decades, there is much interest to study various factors infuencing the development of phytoplankton in relation to the physico-chemical attributes. 9‒12 Changes in the phytoplankton community of different types of lakes also assessed the trophic status and environmental quality of the lakes. Algae (Phytoplankton) are photoautotrophic organisms having chlorophyll ‘a’ and unicellular reproductive structures. It is highly diverse group, which are important for aquatic habitats. 13 A preliminary study on the primary productivity of Nachiketa Tal has been done by Singh et al. 14 A factual report of the water quality of the lake is also available. 15 So the present study was carried out in order to determine the composition, density and diversity of Phytoplankton of Nachiketa Tal and the infuence of physico-chemical variables on them. Materials and methods Nachiketa Tal is located between latitude N 30°38.666’ N and longitude E 078°28.362’ E at an altitude of 2,453m above m.s.l. in Garhwal Himalaya. The area of Nachiketa Tal is 0.49 ha. It is elliptical in shape, measuring about 132 m in length and 58 m width (Figure 1). The lake remains occasionally covered with thin sheet of ice during the winter months of January and February. The lake depth varies from season to season and attains its maximum depth during rainy season and has no noticeable inlet as well as outlet. During the major part of the year, Nachiketa Tal remains shallow. The runoff from the forest deposited sediments in the lake bed. Monthly sampling was undertaken at 08:00 to 10:00 hrs during the one annual cycle (May 2014 to April 2015). Four sampling sites (S 1, S 2, S 3, S 4 ) were identifed for covering the entire ecosystem for collecting data on the physico-chemical parameters and phytoplankton community of the Nachiketa Tal. For physico-chemical parameters, fve replicates of samples from each sampling site were taken for each parameter and their mean value was computed. Water temperature was recorded with the help of the Centigrade (0-110°C) thermometer; electrical conductivity and pH of the sample were measured with the help of the Toshcon Multiparameter Analyser. Nitrates, phosphates, sulphates were determined by using Spectrophotometer (Model –UV-VIS Systronics 117 series). Dissolved Oxygen, total hardness, BOD, alkalinity, calcium, magnesium etc. were measured followed the method outlined in Wetzel and Likens, 16 APHA. 17 For phytoplankton, from each sampling site, fve liter of sample was passed through silk plankton net of mesh size 20 µm and was fxed through 4% formalin solution into sample bottles. Enumeration Volume 2 Issue 2 - 2018 Ramesh C Sharma,Vijayta Tiwari Department of Environmental Sciences, HNB Garhwal University, India Correspondence: Vijayta Tiwari, Department of Environmental Sciences, HNB Garhwal University (A Central University), Srinagar-Garhwal, Uttarakhand, India, Email vijayta29@gmail.com Received: December 23, 2017 | Published: March 02, 2018 Abstract The study deals with the assessment of physico-chemical parameters and phytoplankton diversity of Nachiketa Tal. The lake was monitored for one annual cycle (May 2014-April 2015). A total of 71 taxa of phytoplankton belonging to 57 genera were recorded. Phytoplankton in the lake are represented by six major families, Bacillariophyceae (22), Chlorophyceae (37), Cyanophyceae (6), Xanthopyceae (2), Dinophyceae (2) and Euglenophyceae (2). The overall phytoplankton density was found to be abundant (1401±325.60 ind. l -1 ) in winter season, declined in monsoon season (457.50±17.83 ind. l -1 ) but the population of Cyanophyceae and Euglenophyceae was found to be high (174.33±37.09 ind. l -1 ) and (24.33±5.89 ind. l -1 ) respectively in summer season. Results showed that the increases in turbidity, TDS in monsoon season are the driving factors for decreasing the phytoplankton density in the lake. Pearson’s correlation and CCA calculated between environmental variables and phytoplankton diversity showed that the distribution of phytoplankton in the lake is dependent on the variabilities of physico-chemical variables. Keywords: phytoplankton, himalaya, lake, physico-chemical Biodiversity Int J. 2018;2(2):102-110 © 2018 Sharma et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 102 Biodiversity International Journal Research Article Open Access