Spatial-Temporal Variations of Zooplankton in Relation to Selected Limnological Parameters: A Case of Kisii Town Wastewater Treatment Plant, Kisii County, Kenya

Zooplankton have been used as bioindicators of water quality. In this study, we assessed the spatial-temporal variations of zooplankton in the Kisii town wastewater treatment plant and how they were influenced by limnological parameters between May and August 2021. Triplicate zooplankton samples were collected monthly for laboratory analysis. Physical parameters were measured in situ using a YSI multi-parameter probe while triplicate wastewater samples were collected for chemical parameters analyses ex situ. Eleven (11) zooplankton species were identified belonging to three groups. Cladocera was represented by 5 species (45.5 %), Rotifera by 4 species (36.4 %), and Copepoda by 2 species (18.2 %). The total zooplankton density recorded was 515IndL-1 with the family Cladocera dominating (57.7 %) followed by Copepoda (22.8 %) then Rotifera (19.5 %) with the least number in the population density. The limnological parameters measurements indicate considerable wastewater pollutant removal during polishing but negatively influenced zooplankton diversity. Therefore, zooplankton can be used to monitor wastewater treatment progress.