Evaluation of Some Heavy Metals and Total Petroleum Hydrocarbon in Water and Palaemonid Shrimps (Macrobrachium vollenhovenii) of Egboko River, Warri, Delta State, Nigeria

Aims: To compare the levels of heavy metals and total petroleum hydrocarbons in water and Macrobrachium vollenhovenii samples from different locations of anthropogenic activities.

Study Design: Factorial design.

Place and Duration of Study: Egbokodo River, located in Warri South Local Government Area of Delta State, Nigeria, between October, 2014 and March, 2016.

Methodology: Four (4) stations were surveyed. Station 1 (control) was located upstream and undisturbed, Station 2 had various domestic disturbances, Station 3 was disturbed with dredging activities and Station 4 was exposed to oil spill. Surface water samples were collected from each stations using 250 ml sampling bottles and were analysed in the laboratory for heavy metals (Fe, Mn, Cu, V, Pb and Cd) using a Perkin Elmer 3110 model Atomic Absorption Spectrophotometer (ASS) and total hydrocarbons (TPH) was analysed using an infrared spectrophotometer (IR-Spec) at a wavelength of about 3.425 μm. All values were recorded in mg/L. 30 representatives of Macrobrachium vollenhovenii were collected from each station and were digested and analysed for Fe, Mn, Cu, V, Pb, Cd using a Perkin Elmer 3110 model Atomic Absorption Spectrophotometer (ASS), and TPH in whole shrimp was analysed using Gas chromatography with flame ionization detector (GC-FID). Data was analysed using one way analysis of variance (ANOVA) at probability level of 0.05. Duncan multiple range test was used to detect the locations of the significant differences.

Results: The concentrations of iron and lead in the water and Macrobrachium vollenhovenii at Station 4 > Stations 3 and 2 > Station 1. This indicates correlation between the levels of parameters observed in the water and Macrobrachium vollenhovenii samples with the anthropogenic activities carried out at the respective locations. A constant increase in the levels of lead on advancement towards Station 4 further suggests anthropogenic impacts. The sequence of the parameters in the entire shrimp samples was Fe > Cu > TPH > V > Cd >Pb>Mn; while the sequence in the water was Fe > TPH > Cd > V > Cu >Pb>Mn. This sequence indicates a high affinity for iron and copper in the shrimps. This is due to the essentiality of iron in cytochromes and protein and copper in respiratory pigment haemocyanin and metalloenzyme. Distinctively high levels of cadmium, lead and total petroleum hydrocarbon observed in the tissues of Macrobrachium vollenhovenii representatives at impacted stations can be traced to the background levels in the aqueous phase.

Conclusion: Results indicate that the differences in activities at the impacted sites were associated with differences in metals among the sites and shrimp. This implies that anthropogenic activities had impacts on the aquatic equilibrium of Egbokodo River and there was corresponding response of the physiology of the palaemonid shrimps to the perturbations.