Organochlorine pesticides and heavy metals in fish from Lake Awassa, Ethiopia: Insights from stable isotope analysis

The levels and bioaccumulation of organochlorine pesticides (OCPs) and heavy metals were studied in muscle and liver of three fish species, with two trophic levels, from Lake Awassa, Ethiopia. DDTs were the predominant organic pollutant in all species with a maximum level of 73.28 ng g−1 wet weight (ww). p,p′-DDE was the predominate congener and showed a significant (p < 0.001) relationship with δ15N, which indicates that DDTs could biomagnified in the food web of the lake. Generally, high levels of heavy metals (Cd, Co, Cr, Cu, Ni, Pb, Zn and Hg) were found in liver samples as compared to muscles. The levels of Cd, Co, Cu, Ni, and Pb in liver samples showed negative correlation with δ15N. They were found markedly higher in the lower trophic level fish species (p < 0.05) that indicates biodilution whereas; Zn level showed positive correlation with δ15N.

► OCPs and heavy metals bioaccumulation examined in fish species from Lake Awassa - Ethiopia. ► Levels of DDTs and heavy metals varied among the studied fish species. ► p,p′-DDE, predominate congener, showed significant relationship with δ15N. ► Most of the heavy metals showed negative correlation with δ15N.