Metal behaviour in water, sediment and fish from the St Lucia system: implications for public health and ecosystem impact.

Abstract

The purpose of this study is to assess metal concentrations and their bioavailability, and relate them to concentrations in fish tissues (gill, muscle and skin) as part of the ecotoxicological and public health assessment of the St Lucia system. Eight metals from six sites (Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and five metals (Cu, Fe, Mn, Pb and Zn) from 60 fish, Oreochromis mossambicus, were analysed. Dissolved metal concentrations were highest in the north lake and lowest at the estuary. Sediment metal concentrations were highest in the north lake and lowest in the south lake. Most sediment metals displayed minimal to no anthropogenic enrichment. Normalisation with Fe showed all linear regressions as significant (p < 0.01) and Cr, Cu, Mn, Ni and Zn had R2 values well above 0.9. Only sediment Ni values were above the ERM. Tissue Cu, Fe and Pb concentrations were highest in the gills and Mn and Zn concentrations were highest in the skin. Skin Mn concentrations were highest as compared to the gills and muscle for all sites. The spatial differences in metal concentrations and BCF values for St Lucia suggest distinct populations of fish in the different areas of St Lucia. All concentrations of metals in fish tissues were below the permissible values indicating low human health threat. While higher sediment concentrations justified the economic benefit of mining, evidence of natural enrichment emphasised the need for continual conservation of the greater St Lucia area.