Detection of suitable zooplankton from three taxonomic groups for application in biomanipulation

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Many lentic water bodies of the world are under the threat of cultural eutrophication and experience problems associated with algal blooms. Biomanipulation is a useful technique applied to control algal blooms by deliberate alteration of an ecosystem through addition and removal of organisms. The feeding behavior of zooplankton has been applied in biomanipulation in controlling algal densities and to accelerate ecosystem recovery. For this, it is important to select the most efficient filter feeders. The present experiment was carried out to assess the grazing ability of five different zooplankton species belonging to three taxonomic groups, Cladocera, Copepoda and Ostracoda. Filtering efficiency of each algal species by selected zooplankton species were assessed by counting algal cells in each zooplankton introduced systems. Specific growth rate was calculated using the equation (ln N 1 -ln N 0 ) / (t 1 -t 0 ) where, N 0 (cells/µl) and N 1 (cells/µl) are cell counts at times t 0 (day) and t 1 (day) respectively. The results indicated that zooplankton used in the experiment possess varied capacities of grazing on different species of algae. Chlorella sp. was well controlled by Ceriodaphnia cornuta whereas Crucigenia sp. was controlled better with the Stenocypris sp. Although species of Scenedesmus are favored by many zoopklankton as a food, it was better controlled by the members of the group Ostracoda and also by C. cornuta. Even though Monoraphidium sp. was controlled better by all the study species of zooplankton, C. cornuta showed the highest performances followed by ostracods.