Feeding response of Daphnia cf. similis to different concentration gradients of Microcystis and its implication for preventing algal blooming

Abstract

Daphnia are important components of zooplankton communities in lakes, ponds and reservoirs. Currently freshwater ecosystems are affected worldwide by Cyanobacterial blooms through the process of eutrophication. The objective of this study was to provide experimental evidence to the response of Daphnia to various concentrations of Microcystis. The experiment contained four treatments and two controls each with three replicates. The first control contained D. cf. similis without Microcystis and the second control contained Microcystis without D.cf. similis. The remaining four treatments contained both D. cf. similis and Microcystis at different concentration of Microcystis.. The results showed a significant negative relationships between D. cf. Similis and Microcystis across the treatments (F=294.5; p<0.00). From the four Microcystis concentration gradients, we found mortality of D. cf. Similis in HMC (high Microcystis concentration) and 67% of the original HMC gradient while in the other treatments, in 43% and 22% original HMC treatment, D. cf. Similis reproduce and attain high density. Therefore, from these results it is concluded that D. cf. similis can control the growth of Microcystis if the concentration is low but they cannot reduce an already existing bloom.