Abstract
Urban ecosystems are often characterized by the receipt of pollutants, especially heavy metals from diverse anthropogenic activities. To better understand the distribution of heavy metals (Cd, Cu, Pb, Mn and Zn), Austroaeschna inermis from five different sites (Unilag, Mile 12, Olushosun Dump site, Imoshe and Badagry) in Lagos, sediments from the respective sites were assessed. This was followed by assessment of lipid peroxidation product; Malondialdehyde (MDA) and antioxidative stress enzymes; superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and reduced glutathione (GSH) in A. inermis. The results indicate widespread heavy metal distribution with Mn and Zn having the highest concentrations of 13.369±0.800 mg/kg and 21.473±2.001 mg/kg in sediment samples from Mile 12 and Olushosun Dump site respectively. Only Cd was bioaccumulated at two sites (Unilag and Badagry) with biota to soil accumulation factor (BSAF) of approximately 2. The oxidative stress biomarkers assessment in the insects did not indicate any trend to link heavy metal concentrations with respective sites. However there was strong (r ≥ 0.5 < 0.7) to very strong (r ≥ 0.7) positive correlation between Pb concentrations in A. inermis and most biomarkers. All enzymes and MDA showed negative correlation with the other heavy metals with values mostly between strong (r ≥ -0. 5< -0.7) to very strong (r ≥ -0.7) negative. The findings from this study reaffirms the ubiquity of heavy metals in the City of Lagos and the relevance of the insects as pollution indicators were discussed.
Key words: Biomonitoring, urban ecology, pollution, biomagnification.
