Kifle, Demeke (PhD)Fetahi, Tadesse (PhD)Tialye, Aynalem2019-08-012023-11-182019-08-012023-11-182018-07-05http://etd.aau.edu.et/handle/12345678/18705Blooms of Microcystis aeruginosa frequently occur in many eutrophic lakes in Ethiopia,however, there is very little experimental study on the relationship between Microcystis and Zooplankton from Ethiopian waters. The effects of different concentrations of toxic M. aeruginosa on two common freshwater zooplankton Cladoceran (Moina micrura)and Cyclopoid were investigated in laboratory experiments. The main purpose of this study was to examine if there is a difference in the development of tolerance to toxic Microcystis among two species of zooplankton copepoda (Cyclopoid) and a cladocera (Moina micrura )exposed to toxic Microcystis. We tested whether exposure to a toxic strain of cyanobacteria (Microcystis) affects survival, and growth, of a common herbivore, Cyclopoid and cladoceran(Moina micrura). In the experiments, cultures from the lakes will be test at five concentrations of toxic Microcystis aeruginosa: 0%, 20%, 50%, 80% and 100%.After 16 days, we compare the ability of these two populations to withstand the toxic Microcystis by assessing survivorship, and growth rate.Field study showed that Surface water temperatures of all sampling sites were within the range of variation reported for most tropical water bodies (23- 25ºC). Surface water DO(mg L-1), which was varied from 5.48 of the HEPP site to 6.99 of the MetoAleka shore site. Mean levels of nitratevaried between 0.11 HEPP and 0.224 mg L-1 Tannery, while those of ammonia ranged from 0.054 of the MetoAlekashore site to 0.033 Tannery mg L-1. Mean SRP (in mg L-1) 0.083 and 0.09 MetoAleka shore, TP, ranged from 0.254 mg L-1 Tannery of the site to 0.298 mg L-1 of the MetoAleka shore). The phytoplankton communities of all sampling sites were dominated, in terms abundance, by three alga groups, Cyanobacteria (blue-green algae), Bacillariophyceae (diatoms) and Chlorophyceae (green algae). Chlorophyceae was the most species-rich taxonomic group, followed by Cyanophyceae and Bacillariophyceae. The most abundance species were Microcystis sp, and Planktothrix cf.agardhii in Lake Koka. The zooplankton community in Lake Koka was dominated by the copepod which accounted for about 56% of total zooplankton abundance. From experimental result we get more survival rate for cladoceran treatment and low for copepod treatment. It can be suggested that biomanuplation controlling methods can be used to improve water quality in Lake Koka .enBiomanuplationCyanobacterial BloomEutrophicationGrazingMicrocystis SppZooplanktonThesis