Comparative Studies of the Mineral Composition of Two Age-Groups of Heterobranchus bidorsalis Exposed to Graded Concentrations of Bonny-light Crude Oil

Abstract

The macro-and trace-element component of the mineral composition of Heterobranchus bidorsalis juveniles (JVs)(14.06 ± 0.38g) and adults (Ads) (138.24 ± 0.16g) were studied on exposure to graded concentrations (1.00 – 8.00 ml L^-1‑) of Bonny-light crude oil (BLCO).  The experiment was monitored for 4 days (toxicity) and 42 days (recovery) periods.  Insignificant decreases (P > 0.05) in the values of sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), phosphorus (P), iron (Fe), vanadium (Va), lead (Pb) and manganese (Mn) in the H. bidorsalis JVs and Ads corresponded with the increasing concentrations of BLCO in water.  The values of Na, K, Mg, Ca, P, Zn Fe, Va Pb and Mn recorded in the JVs were generally lower than those recorded in the ADs and the control fish.  Although the removal of the oil pollutant elicited increases in the values of the macro elements (Na, K, Mg Ca and Pb) in the magnitudes of 15% at day 14, 20% at day 28 and 20% at day 42, no definite pattern of increases was established for the trace elements (Zn, Fe, Va Pb and Mn).  The apparent depletion in the values of the macro elements with the increasing concentrations of BLCO implies that the crude oil compounds might have impacted negatively on the deposition of these elements in the fish tissues.  In addition, the higher values of the trace elements in the ADs than in the JVs implies that irrespective of the BLCO concentration, the Ads incorporated more trace elements in their body tissues than the JVs although the differences in values were insignificant