Effects of Water-Soluble Fractions of Used Crankcase Oil on Some Physiological Parameters of the Nile Tilapia (Oreochromis Niloticus)

Abstract

Used crankcase oil is disposed off indiscriminately and it eventually finds its way into the aquatic environment resulting in surface and ground water contamination by complex interacting chemicals and substances. Polycyclic aromatic hydrocarbons (PAHs), heavy metals, additives, antioxidants and trace levels of chlorinated solvents have been detected in used engine oil and these pose a great risk to fish populations and the human consumer of fish. This study (i) investigated the sublethal effects of water soluble fractions of used crankcase oil on feed conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR), length and weight and muscle and liver glycogen of Oreochromis niloticus fingerlings, (ii) investigated the sublethal effects of the water soluble fractions (wsf) of used crankcase oil on the condition factor of O. niloticus fingerlings, (iii) assessed the bioaccumulation of metals in the liver, gill and muscle of O. niloticus fingerlings exposed to wsf of used crankcase oil, (iv) determined the sublethal effects of used crankcase oil on the haemotological indices of O. niloticus fingerlings, (v) investigated the effects of used crankcase oil on some selected enzymatic activities in O. niloticus fingerlings.The water soluble fractions (wsf) of the used crankcase oil was prepared using the method described by Anderson, Neef, Cox & HighTower (1974) whilethe 96hr static renewal bioassay technique was employed to obtain the median lethal concentration (LC50) from which the sublethal concentrations (definitive values) were made.One-way analysis of variance (ANOVA) was used to interpret the data on the mean concentration of metals in the experimental water and fish organs as well as the variations in mean values of liver and muscle glycogen and the growth performance and feed utilization of the experimental fish.Fishshowed significantly reduced weight (P < 0.05) with values of 1.1, 1.5, 1.6 and 1.8 g respectively. However, fingerlings in the control (0.00 ml/L) and the least sublethal concentration of 8.75 ml/L had significant increases in weight from 6.30g initial weight to 20.10g and 16.81g in that order. There was a strong positive correlation between the weight and length of fish with r = 0.861. The analysis of variance of growth performance between groups and within groups was significantly different (P < 0.05) during the exposure period. Liver glycogen decreased with increasing time in the fish groups in the sublethal concentrations with glycogen values at 0.68, 0.80, 0.75, 0.55 and 0.30 mg/L. Similarly muscle glycogen decreased as exposure time progressed with reduced values at 0.04, 0.04, 0.03, 0.03, and 0.02 in the ascending order of the sublethal concentrations. Conversely, the liver and muscle glycogen values increased significantly (P < 0.05) in fingerlings in the control group. Statistically significant (P < 0.05) low values of FCR, and PER were observed in the control when compared with the higher sublethal concentrations.These statistical trends show evidence of stress and an impairment of carbohydrate metabolism in the experimental fish as well as a decreased capacity to efficiently utilize protein when exposed to used Crankcase Oil. O. niloticus fingerlings had a mean condition value of less than one (< 1) showing a condition below mean average. The concentration of metals and other elements in the used crankcase oil was in the order Ca> Zn> Na> Fe> Si> Al> Cu>Mn> Br > Pb, while the muscles, gills and liver had concentrations of metals in the following order: Fe > Zn > Mn > Cu > Pb > Cr. There was a decrease in circulating erythrocytes, from 1.16 to 0.62μl as well as decreases in MCV from 109.3 to 34.2μl and blood platelets from 274.0 to 0.0μl respectively. Conversely, the result showed increases in WBC, LY, MO, GR, and MCHC from 6.5 to 27. 8, 4.1 to 20.9, 0.7 to 2.8, 1.8 to 5.9 and 125.5 to 198.9μl in that order. There was a significant difference (P < 0.05), between WBC and RBC of fish in the control tank and those in the sublethal concentrations.The activities of the enzymes ALP and ALAT revealed a significant increase (P < 0.05) in both cases when compared to the control. The concentration levels for ALP in the highest sublethal concentrations were 256.06±0.441, 200.12±0.831, and 100.00±0.762 iu in the fish muscle, liver and gills respectivelely. While in the control, the levels were 35.00, 16.65 and 13.35 iu in the muscle, liver and gills in the same order. ALT concentration levels were 462.41±0.098, 430.425±0.126 and 398.00±0.056iu in the fish muscle, liver and gills respectivelely at the highest sublethal concentration. Concentration levels at the control tank were 5.712±0.031, 48.137±0.005 and 5.195±0.038iu in the fish muscle, liver and gills in that order. Exposure of the test fish to the wsf of used crankcase oil resulted in retarded growth as seen in the reduction in weight and constancy of length of fish in the higher sublethal concentrations.O. niloticus fingerlings had a poor feed conversion capability in the presence of used crankcase oil evidenced by decreases in muscle and liver glycogen at the higher sublethal concentrations. Metals are capable of accumulating in the tissues of fish when concentration levels are high.The unregulated disposal of used crankcase oil poses a great threat to the health of the environment. Consequently, government at all levels should control this indiscriminate practice through legislation and by creating collection centres forused crankcase oil. Bioremediation, recycling and other processes should be put in place to ensure proper disposal and to prevent the pollution of the environment.