Water resources plays a key role in the aquaculture, wild fish, domestic use enhances socio-economic development and hence contribute immensely to realization of food and nutritional security. However, since the onset of fish cage culture in the lake, increasing human population created similar increasing demands in agricultural lands, water and with expanding settlements. The changing climatic conditions and fluctuating precipitation, emerging micropollutants and environmental stressors, all contribute to the multiple environmental pressures which threatens the water quality in the lake at large, resulting in degradation of fish and other flora and faunal habitats, increasing vulnerability of endangered species, risks to public health and livelihoods.This pushed for environmental assessment study of the ecological status of the water quality and characterization of pollutants at selected sites from January 2022 to April 2023. In-situ measurement of key water quality parameters was made at eight sampling sites, each having three points using a HANNA HI9829 multi-parameter meter. Ekman grab was used to collect triplicate hauls of the benthic macroinvertebrates samples sieved using 500 micron sorted to species level, nutrients and chlorophyll-a samples was collected and analyzed following standard methods of analysis. Dissolved oxygen, temperature, pH, ORP, Total nitrogen, Total phosphorous ranged from 1.87 – 8.19 mg/L, 23.48 – 29.65 ⁰C, 6.02 – 8.82, -304.40 – 478.3mV, 86.53 – 321.79µg/L, 14.71 – 384.71µg/L respectively. Thus an indication of hypoxic, acidic and toxic environment of pollutants in increased concentrations and lots of dead and decaying material in the water column that cannot be easily cleared or decomposed. Chlorophyll- a as primary productivity and algal biomass indicator tool, recorded a range of 8.96- 294.75µg/L thus an indication of intense eutrophication. TN:TP ratio determines the limiting nutrient in the waterbody, during the study all stations exhibited nitrogen limitation because the ratio of all the sites was below the required standard of > 15. All sites sampled had high tolerance values >5 in benthic macroinvertebrates an indicator of highly polluted ecosystem where an organism resides. This endurance to pollutants for a period of time in a disturbed environment with poor water quality, needs to be regenerated through policy formulation to stem the menace. Waste water planning and management, long term monitoring needs to be sustained to guide on expanding urban development, anthropogenic pressures, impact of climate change and better management of Lake Victoria aquatic ecosystem for harnessing the blue economic growth.
Keywords: Cage culture, point source, non-point source, pollution, macroinvertebrates, Ecology, Lake Victoria, Winam gulf.