Bioaccumulation Of Heavy Metals In The Catfish Chrysicthys Nigrodigitatus From Taylor Creek, Southern Nigeria

Abstract

The discharge of liquid effluents either untreated or with only primary treatment into Etelebou Creek, a tributary of Taylor Creek has led to the extensive contamination of Taylor Creek by heavy metals. The catfish species, C. nigrodigitatus and other environmental segments were collected from five sites along Taylor Creek, southern Nigeria, and some metals determined by flame atomic absorption spectrophotometry. The concentration levels of the metals in C. nigrodigitatus were higher than values reported in the literature for fresh fish and may lead to a higher risk and harmful effects. The bivariate regression models relating metals in C. nigrodigitatus and metals in the surface waters were significant (R2 ≥ 0.7134). The Log (bio-concentration factors or BCF) of Cr and Zn in C. nigrodigitatus were the highest, whereas Ni was the lowest. The ecological distribution of the log (BCF) values was, for all the heavy metals, moderately stable over the Creek. All log-transformed biomagnification factors (BMF) in the Creek were positive, which indicates that the metal concentration was higher in C. nigrodigitatus than in suspended particulate matter (SPM). The absolute log (BMF) values of heavy metals can therefore be ranked in order of decreasing magnitude: Fe (4.06) > Zn (2.87) > Mn (2.59) > Cr (1.95) > Pb (1.90) > Ni (1.82) > Cd (1.55). This sequence indicates that toxic metals such as Cd, Cr and Pb are undergoing significant bio-reduction from SPM to C. nigrodigitatus. The degree of
correlation between the metals was different in C. nigrodigitatus, which suggests that the sources of the metals, polluting Taylor Creek were diverse.