The Effect of E-waste Dumpsite Soil on Cultured Tilapia Fish and Associated Microorganisms

Aim: To evaluate the toxicological effect of e-waste on cultured tilapia and identifying microorganisms associated with the tilapia aquaria polluted with soil from e-waste dumpsite.

Study Design: The soil samples, water from the polluted aquaria and the harvested fish were then subjected to physicochemical, microbiological, proximate and toxicological analyses.

Place and Duration of Study: Lagos State and the study were undertaken for five weeks.

Methodology: The organic contents were determined using gravimetric techniques, nitrogen content was determined using kjeldhal method, exchangeable bases were determined using flame emission spectrometry and EDTA classical methods titration, heavy metals determination were estimated using atomic absorption spectrometer, the toxicological study and the microbiological analyses were carried out using standard methods.

Results: The physiochemical parameters of the soil samples differs with higher heavy metals values in e-waste soil sample. Some of microorganisms isolated were of the genera; Bacillus, Proteus, Listeria, Pseudomonas, Lactobacillus, Aspergillus, Articolospora, Penicillium, Rhizopus, Mucor, and Zoopage. The types and number of microorganisms from the e-waste dumpsite soil, aquaria polluted with soil from e-waste dumpsite differs from those from controls. The ash content (9.68a±0.08 - 14.29e±0.51) showed improvement over the control (9.49a±0.20). Rise in fibre content of the tissue (0.86b±0.02 - 0.98c±0.01) was also observed over the control. Deformities of the gills and livers of the fish were observed while the packed cell volume, haemoglobin, oxygen carrying capacity and the red blood cell of fish from polluted aquaria were lower than that of fish from unpolluted aquaria. Immunological responses were also observed.

Conclusion: The histopathological and the haematological effects alongside the effect on the proximate composition and the microbial isolate variation in the soil samples and aquaria showed the adverse effect of the e-waste on the fish and its environment.