Relationships between heavy metals in the catfish, <i>Chrysicthys nigrodigitatus</i>, water column and sediments of taylor creek, southern Nigeria

Abstract

Heavy metals in the aquatic environment have to date originated basically from naturally occurring geochemical resources. Nonetheless, this has been enhanced by anthropogenic activities resulting in pollution. Consequently, relationships and partitioning of heavy metals in the dissolved phase, suspended particulate matter (SPM), sediments and the catfish C. nigrodigitatus were investigated in five selected sites along Taylor creek, southern Nigeria. The degree of relationships between the various metals was dissimilar in each of the investigated matrices. In the matrices, not several significant relationships (PO.05) were obtained. Only Ni-Cd (r=0.95), Mn-Cd (r=0.63), Mn-Ni (r=0.64) were associated in the sediments and in SPM, Fe-Cr (r=0.54) and Zn-Ni (r=0.72), which suggests that the sources were not common for both matrices. In the dissolved phase, no strong relationships (PO.05) between the heavy metals were obvious. The best relationships were observed for Ni-Zn (r=0.72) and Cd-Pb (r=0.65). Partitioning coefficients (£d) of heavy metals between dissolved phase and SPM were generally low, which is typical for fresh water ecosystems and fairly stable over the creek all through the seasons. Furthermore, the bio-concentration factors (BCFs) of C. nigrodigitatus were low unlike those of other natural waters. Conversely, the state of the aquatic ecosystem indicates that the heavy metals could contribute to inferior biodiversity and shifts in community composition from sensitive to tolerant taxa that also signifies that the heavy metals in C. nigrodigitatus exceeded the Risk Based Consumption Limits, based on an adult body weight of 70 kg and 16 Fish Meals/Month, indicating that consumers of C. nigrodigitatus from the creek may be exposed to neurotoxins.

Keywords: Cat fish, Chrysicthys nigrodigitatus, heavy metals, Nigeria