Seasonal variation in zooplankton dynamics of lake Siliserh, India

Siliserh Lake is an important water body of Rajasthan state. In Siliserh Lake, zooplankton community composed mainly of Crustaceans (particularly Copepoda and Cladocera) and Rotifers. Other plankton groups were also observed at low density and frequency, such as Protozoa, Ostracoda and Insecta. Plankton samples were collected by means of horizontal haul, using plankton net (No.25) with a mesh size of 55 µm. In the present study. The correlation between various physico-chemical parameters and zooplankton groups were tested using Pearson-Moment Correlation. Zooplankton population was observed to be composed of 37 species belonging to 29 genera. Out of 37 species, 16 represented Rotifera, 6 Copepoda, 7 Cladocera, 3 Protozoa, 3 Ostracoda and 2 Insecta. The total density of zooplankton varied between 12.44 x 101 L-1 and 144.84 x 101 L-1 during the study period. Minimum species density was recorded in the monsoon season, while the summer season was characterized by maximum zooplankton density. Total zooplankton density was found positively correlated with total hardness, Mg hardness, and free CO2 and negatively correlated with conductivity, TS, TDS of water. Copepoda was the dominant group both in winter and summer season. So the present study validates the fact that this freshwater lake remains oligotrophic during summer and winter season but becomes loaded with nutrients during monsoon season reaching eutrophic condition.