Acute toxicity of industrial detergent (Neatex) and corrosion inhibitor (Norust CR486) to early stages of cichlids: Tilapia guineensis

Abstract

The biological effects of uncontrolled discharge of industrial chemicals into the Niger Delta environment of Nigeria need to be investigated, and the acute toxicity assay represents a useful tool. This study investigated the toxicity of two chemicals (Neatex and Norust CR 486) to early life stages of an economically important fish (Tilapia guinensis) from fresh and brackish waters of the Niger Delta environment. The American Society for Testing and Material-recommended semi-static renewal bio-assay was adopted. Tilapia guineensis (7 d old) were exposed to varying concentrations of the chemicals, and LC50 values were measured at 96 h. Results indicated that exposure durations, concentrations and environmental conditions influenced the effects of the chemicals. The estimated 96-h LC50 values from the fresh and brackish water tests were 7.91 and 15.32 mg l−1 for Neatex and 4.03 and 5.30 mg l−1 for Norust CR 486, respectively. The results showed that Norust CR 486 was more toxic than Neatex. The estimated 96-h LC50 and mean percentage mortality values for fresh and brackish water tests were statistically significant only for Neatex at P<0.05 (t-value=11.91) and P<0.05 (t-value=3.21), respectively. There were also significant differences between the test and control experiments for both chemicals at P<0.05. The observed sensitivity of the fish to both chemicals provides a rationale for regulatory surveillance of the chemicals in the Niger Delta environment.