The use of herbicides for increased food production may pose risk to non-target organisms. This study evaluated the acute toxicity, genotoxic, biochemical, and histological biomarkers of subacute concentrations of paraquat and glyphosate in Oreochromis niloticus (Nile Tilapia) for 28 days following standard methods. Glyphosate (96 hLC50 value-1.23 mg/L) was 9x more toxic than paraquat (96 hLC50 value-11.20 mg/L) against O. niloticus. Average micronucleated cells were significantly higher in the erythrocytes of O. niloticus exposed to the higher (1.12 mg/L) concentration of paraquat at day 14, both subacute concentrations of paraquat at day 28, and lower concentration (0.01 mg/L) of glyphosate at days 14 and 28 compared to the other treatments and controls. Biochemical biomarkers (MDA and GST) activities were significantly higher at both subacute concentrations of the herbicides in the exposed fish compared to the controls at day 28 only. GSH activity was significantly higher in the 0.11 mg/L paraquat concentration while SOD activity was significantly lower at both subacute concentrations of glyphosate in exposed fish compared to controls at day 28. Histological alterations observed were mild to severe shortening of the gill primary lamellar and hepatic portal inflammation of exposed fish compared to the controls. This study demonstrates the risk to non-target organisms due to herbicides' run-off from agricultural farmlands into aquatic ecosystems at environmentally relevant or subacute concentrations. Sensitization on the responsible use of pesticides is recommended to promote responsible consumption and production and sustain life below water (United Nations Sustainable Development Goals 12 and 14 respectively).
