Study of vertical distribution dynamics of zooplankton in a thermally stratified warm monomictic lake of Kashmir Himalaya

In the present study, we investigated how stratification patterns and the related physico-chemical characteristics impact the vertical distribution of zooplankton community during the two consecutive stratifications in a warm monomictic lake (Manasbal Lake) in the Ganderbal area of Central Kashmir. Two consecutive events of stratification and deepening of thermocline recorded during the sampling period led to significant changes in the vertical distribution of zooplankton community. Physico-chemical characteristics displayed significant changes with the stratification pattern. Temperature of the surface water (0 m) increased gradually from 13 degrees C to 29 degrees C, resulting in a higher thermal gradient. pH and dissolved oxygen (O-2) displayed clinograde curves with vertical depth. Keratella cochlearis and Polyarthra vulgaris (Rotifers) were most dominant in terms of density and abundance at the thermocline and significantly decreased at the hypolimnion. Cladocera with significant difference along the vertical column showed an epilimnetic distribution with Ceriodaphnia reticulata and Ceriodaphnia quadriangularis being the major contributors. Among copepods, Cyclops viridis was recorded at all depths in greater dominance. Acanthodiaptomus denticornis (Diaptomidae) showed higher abundance from epilimnion to thermocline but decreased at hypolimnion. The results showed that the strong vertical gradient of environmental factors occurs in the Manasbal lake. Among them, dissolved oxygen, water temperature, and nutrients controlled the zooplankton community with higher aggregation above the thermocline. Therefore, the present investigation regarding the dynamic patterns of zooplankton community along the vertical gradient in a stratified lake could be important in monitoring habitats and to understand the ecology of warm monomictic lakes.