2. SEASONAL VARIATIONS OF PHYTOPLANKTON AND THEIR CORRELATION WITH PHYSICO-CHEMICAL PARAMETERS OF KANJIALAKE, NANDANKANAN ZOO, BHUBANESWAR by G.N.INDRESHA1, S.P.PARIDA2 AND A.K.PATRA3
Phytoplankton plays an important role in fresh water ecosystems as bio-indicators and are used as a tool for assessing the water quality. It is necessary to study population dynamics, community structure, species composition, species diversity of phytoplankton while undertaking ecological investigations in aquatic ecosystems, particularly in fresh water ecosystems like Kanjia Lake of Nandankanan Sanctuary. Sampling points were decided by keeping in mind that the sampling points must include shallow and deep regions of the water body, points of inflow, and outflow of water in the lake and anthropogenic activities. The grab samples were collected from four different sites, enough to accurately represent the whole water body to assess their physical and chemical and biological parameters at monthly intervals in the middle of every month between 9:00- 11:00 am.To minimize the changes from collection to analysis, the sample was preserved soon after collection by adding with 10ml of 1% Lugol’s solution.Different physicochemical parameters were measured in the field itself by physical methods or by using Systronics P-4 water analysis kit (E-Merck).The present study shows the phytoplankton density ranged from 3485.625 to 3823.125 nL-1 with mean ± S.D. (3670.312± 157.956) during winter season, 5941.875 to 6751.65 nL-1 with mean ± S.D. (6269.475± 383.2973) during summer season and 3213.75 to 4021.875 nL-1with mean ± S.D. (3521.25± 348.390) during monsoon season.The variations across sites were insignificant and significant over seasons.The total densities of phytoplankton were found to be maximum during summer and minimum during monsoon season. Among different groups of phytoplankton, chlorophyceae, cyanophyceae were found to be maximum during summer and minimum during monsoon whereas bacillariophyceae were found to be maximum during summer and minimum during winter season followed by monsoon. Average of four year density also found to be minimum during monsoon and maximum during summer season. In general higher phytoplankton density was much more pronounced during the summer season than the monsoon periods in the lake.The correlations between phytoplankton density with one or other physicochemical parameters indicate that the density of phytoplankton is dependent on different abiotic factors either directly or indirectly indicating the seasonal variation in physico-chemical and biological parameters, it can be concluded that changes in physicochemical parameters play an important role in seasonal variation in density and diversity and distribution of phytoplankton.
KEY WORDS: Kanjia Lake, phytoplankton, seasonal variation, physico- chemical parameters.