Abstract
BackgroundPollution arising from the noxiousness of palm oil mill effluent (POME) has become a serious threat to aquatic biotas. However, a paucity of information exists on fish response to POME-mediated oxidative stress, lipid peroxidation, haemato-biochemical, enzymatic and ionic changes. This study, therefore, evaluates the effects of 28-day exposure of Heteroclarias, a hybrid catfish, to POME. Juvenile Heteroclarias (n = 350, average weight: 11.90 ± 0.70 g and average length: 9.04 ± 0.71 cm) were exposed to sublethal concentrations (0-control, 4.00, 8.00 and 12.00 mg/l) of POME to determine its effects on red blood cells (RBC), haemoglobin (HB), packed cell volume (PCV), white blood cells (WBC), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC) and mean cell volume (MCV). The activities of alanine aminotransaminase (ALT), aspartate aminotransaminase (AST), lactate dehydrogenase (LDH), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and the levels of malondialdehyde (MDA), calcium (Ca+), potassium (K+), magnesium (Mg2+) and sodium (Na+) ions were also assayed in the gill and liver.ResultsExposure to POME caused significant (p < 0.05) concentration-dependent decrease in RBC, HB, PCV, MCV, MCH and MCHC values, whereas a significant (p < 0.05) concentration-dependent increase in WBC was observed in POME-exposed fish compared to the control. ALT, AST, LDH, GPx, SOD and CAT activities in the gill and liver significantly (p < 0.05) increased in a concentration-dependent manner. MDA level significantly (p < 0.05) increased in the gill relative to control, while in the liver it was insignificantly different. Both tissues exhibited an increase in Ca+, K+, Mg2+ and Na+ levels at the highest toxicant concentration with a rise of 77.93, 38.46, 109.54 and 41.99% recorded for the electrolytes in the gill and 79.17, 26.92, 55.48 and 38.78% in the liver above the control value, respectively. The levels of all the electrolytes except K+ were higher in the gill than the liver and were in the order: Na+ > K+ > Mg+ > Ca2+ in both tissues.ConclusionsThese results may be used as a suitable tool for pollution assessment and policy formulation to mitigate the discharge of untreated POME into aquatic ecosystems and their impacts on resident organisms.
Highlights
Pollution arising from the noxiousness of palm oil mill effluent (POME) has become a serious threat to aquatic biotas
white blood cells (WBC) exhibited a significant (p < 0.05) concentration-dependent increase in the palm oil mill effluents (POME)-exposed fish compared to the control groups (Fig. 1)
The characterised water quality parameters were more than the maximum desirable thresholds recommended by both the local (NSDWQ 2005; Nigeria Industrial Standard (NIS) (Nigerian Industrial Standard) 2007; National Environmental Standard Regulation Enforcement Agency (NESREA) 2011) and international (TDIW 1997; United States Environmental Protection Agency (USEPA) (United States Environmental protection Agency) 2011; World Health Organization (WHO) (World Health Organisation) 2011) regulatory bodies, indicating the extent of POME toxicity
Summary
Pollution arising from the noxiousness of palm oil mill effluent (POME) has become a serious threat to aquatic biotas. Owolabi et al Bulletin of the National Research Centre (2021) 45:220 where oil palm is grown It provides income for farmers and their dependants and has contributed to the Nigerian gross domestic product (GDP). Studies have shown that during oil extraction, 5–7.5 tonnes of water could end up as effluent for every one tonne of palm oil extracted (Okwute and Isu 2007; Wu et al 2009). Most of these palm oil mill effluents (POME), those produced from the small-scale industries, are channelled from the production units, directly without prior treatment, into the aquatic ecosystems. Considering the likely impacts POME may have on fish species, livestock and humans upon being discharged into water bodies, in which hitherto there are no toxicological guidelines concerning its exposure; the need to document vital information that may be useful in mitigating environmental challenges arising from POME is pertinent
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