Antibiotics, algal evaluations and subacute effects of abattoir wastewater on liver function enzymes, genetic and haematologic biomarkers in the freshwater fish, Clarias gariepinus

Abstract

Abattoirs are positioned close to freshwaters in most developing countries where untreated wastewaters are discharged into with potential risk to aquatic life such as fish and ultimately human health. We assessed physicochemical parameters, antibiotics (oxytetracycline and diclofenac) and algal load of effluent collected from a major abattoir in Nigeria. Furthermore, liver function enzymes, genotoxic and haemotoxic effects of subacute concentration (10% of 96 hLC₅₀ value) of the wastewater were evaluated over a period of 28 d in Clarias gariepinus (The African Sharptooth Catfish). The 96 hLC₅₀ value of the abattoir wastewater against C. gariepinus was 154.14 mL/L (15.4%). Nitrates, phosphates, sulphates, chloride, ammonia, TDS, TSS, BOD₅ and heavy metals (Fe and Pb) in the wastewater were above permissible limits while diclofenac and oxytetracycline were below detection limit (BDL). Microalgae in the wastewater were mostly Bacilliariophyta (Navicula spp.) (45.64%) and euglenoids (Euglena and Phacus spp.) (49.48%). Liver function enzymes (LDH, AST, ALT) level were higher in exposed fishes except for ALP which was lower at day 28 compared to control levels. Erythrocytic genotoxic indices (nuclear abnormalities) were significantly higher (p < 0.05) in the exposed fishes particularly at day 28 compared to control. Haematologic indices level such as WBC, MCV MCH, MCHC increased significantly (p < 0.05) while lymphocytes, HGB, RBC, HCT levels decreased significantly (p < 0.05) in the exposed C. gariepinus by day 28 compared to control. These results demonstrate potential adverse effects posed to aquatic fish species in the Ogun River by the discharge of the abattoir effluent. The microalgae species identified in the effluent may be explored for pre-treatment of the effluent before discharge in order to prevent eutrophication and increased pollutant load in the River. The study results will contribute to evidence-based environmental risk management of the River which is relevant to the UN SDGs 6 (clean water and sanitation), 11 (sustainable cities and communities) and 14 (sustaining life below water).