IOSR Journal of Environmental Science, Toxicology and Food Technology (IOSR-JESTFT) e-ISSN: 2319-2402,p- ISSN: 2319-2399.Volume 14, Issue 10 Ser. IV (October 2020), PP 15-20 www.iosrjournals.org DOI: 10.9790/2402-1410041520 www.iosrjournals.org 15 | Page Survey of Phytoplanktons in Makhana Pond Water of North Bihar Anupma Kumari C M Science College, L N Mithila University, Darbhanga Abstract During the present study, phytoplanktons were represented by Cyanophyceae, Chlorophyceae and Bacillariophyceae from Makhana Pond of Darbhanga district. The Chlorophycae was rich in species Diversity being represented by 17-species followed by Cyanophyceae and Bacillariophycae with 6 and 5 species, respectively, in Makhana pond. The phytoplankton density was recorded highest during April 2008 and the lowest during December 2008. It exhibited trimodal pattern of fluctuations during the study period. Among the three peaks, two were in November 2008 and April 2009, and one minor peak in June 2009. In November 2008 it was recorded as 3637 U/L. But in December 2008 its density dropped suddenly to 989 U/L and after that the increase continued till April 2009, where the total phytoplankton population recorded the highest peak (4208 U/L). But in May 2009 the number phytoplankton decreased to 1528 U/. During June to August 2009 there was a trend of decrease in its population. In order of dominance, the phytoplankton were as Chlorophyceae > Bacillariophyceae > Cyanophyceae contiributing 74.6%, 14.0% and 11.4% respectively. The total population of green algae dominated over blue greens and diatoms throughout the study period. The percentage composition of diatoms was more than that of blue greens but during July 2008 to November 2008, July 2009 and August 2009, the former was recorded lesser in number than the later. Gross Primary Productivity (GPP), which is the total rate of photosynthesis including the organic matter used up in respiration during the measurement period was maximum during summer months and minimum during winter months. Key Words: Phytoplanktons, Cyanophyceae, Chlorophyceae, Bacilliophyceae, Gross Primary Productivity --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 26-10-2020 Date of Acceptance: 06-11-2020 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction Phytoplanktons are the autotrophic components of the plankton community and a key factor of ocean, seas and freshwater basis ecosystem. Most phytoplankton are too small to be individually seen with the unaided eye. However when present in high enough numbers they may be appear as a green discoloration of the water due to the presence of chlorophyll within their cells. The growth of Phytoplankton depends on the availability of carbon dioxide, sunlight and nutrients. Phytoplanktons like terrestrial plants require nutrients such as nitrate, phosphate, silicate and calcium at various levels depending on the species. Some phytoplanktons can fix nitrogen and can grow in areas where nitrate concentrations are low. Phytoplanktons are minute and microscopic plants which are able to spend their whole life floating in water. These are important biotic components of an aquatic ecosystem which provide not only the most important food item of the fishes either directly or indirectly but also oxygenate water during their photosynthesis and can be used as an indicator of the trophic phase (Nasar and Dutta Munshi, 1976, Verma and Dutta Munshi, 1987). The density and diversity of phytoplankton are controlled by several physicochemical factors of water (Anupma, 2020: Communicated). Light plays a significant role as an energy source for photosynthesis by phytoplankton. This is the reason behind the presence of the highest number of phytoplankton during summer. Kaufman (1980) suggested that light is a limiting factor for phytoplankton growth. The temperature has been considered as a major environment factor to control their growth (Verma and Dutta Munshi, 1987; Bais et. al., 1995). The proliferation of phytoplankton during summer months could be attributed to the increasing water temperature. This confirms the findings of Wisharad and Mehrotra (1988). Baruah et. al., (1993) and Shivakashi et. al., (1995) also reported maximum growth of algae during summer months. Nutrients like nitrogen and phosphorus provide basic materials for phytoplankton development (Trivedi et. al., 1985; Agrawal et.al., 1990). The high content of phosphate and nitrogen favored phytoplankton growth during the present study. But during August’ 98 and May’ 09 the total phytoplankton population was recorded to be low inspire of high content of nitrogen and phosphate which was due to predation by the abundant zooplankton. The biological productivity of any system whether aquatic or terrestrial involves the trapping of solar energy by chlorophyll bearing plants and its transformation within the system by different organisms at different