Zooplankton Assemblages in kamalpokhari, Bhaktapur and their Responses to Malathion Exposure

Abstract

The present study explored the zooplankton assemblages in Kamalpokhari, Bhaktapur and assessed the impact of Malathion exposure in lab. The physico-chemical parameters like water temperature, pH, dissolved oxygen, alkalinity and hardness were analyzed which were found to be 20℃, 8.8, 5.7 mg/l, 112.5 mg/l and 63 mg/l respectively. Water samples were collected from the pond for the qualitative and quantitative analysis. Zooplankton were collected by the help of plankton net (20 diameter) made of bolting silk (no. 30; mesh size 25 micron). Zooplankton were identified by using identification keys. A total of ten different genus of zooplankton i.e. Cyclops spp, Calanus spp, Daphnia spp, Moina spp, Hemicypris spp, Keratella spp, Brachionus spp, Polyarthra spp, Filinia spp and Paramecium spp were identified. The most abundant and dominant were Cyclops spp, Calanus spp, Daphnia spp and Moina spp which belong to two groups of Crustacea- Copepod and Cladocera respectively. Among the ten different genus of zooplankton, the two groups Copepod (Cyclops spp and Calanus spp) and Cladoceran (Daphnia spp and Moina spp) were cultured for about 15 days. The cultured species of Copepods and Cladocerans were counted and kept in different beakers of 100 ml and diferent concentrations of Malathion like 0.01 µl/L, 0.05 µl/L and 0.1 µl/L were injected. The number of species were counted every day after interval of every 24 hours for 4 days. The study showed that the number of copepod and cladoceran were affected by Malathion. The survivality rate of both the specimens decreased when 0.01µl/L, 0.05µl/L and 0.1µl/L doses of Malathion were injected with respect to the time period. Among the two species, the mortality of copepod increased slowly while the mortality of cladoceran increased rapidly than copepod. The survivality of copepod and cladoceran decreased upto 70% for both at 0.01µl/L till 96 hours. The survivality of copepod and cladoceran decreased upto 60% and 55% respectively at 0.05µl/L till 96 hours. The survivality rate of copepod and cladoceran decreased upto 35% and 30% respectively till 96 hours at the concentration of 0.1µl/L.