Acute toxicity of sugarcane and kraft pulp and paper mill effluents to the native Chironomus species (Diptera: Chironomidae)

Abstract

Toxicity to fish has potentially been influenced by anthropogenic activities in a lacustrine environment. This study aimed to determine the median lethal concentration (LC50) of Chironomus sp, subjected to different concentrations of industrial effluents from the sugarcane, kraft pulp and paper mill factories in the upper catchments of Lake Victoria Basin, Kenya, using the median (LC50) of fourth-instar larvae. Native Chironomus species for toxicity tests in the laboratory were sampled upstream and downstream in Rivers Nzoia and Mbogo within the LVB. They were then exposed to effluents taken from Chemelil and Webuye Paper Mill factories. Effluents were more toxic to midges sampled upstream of the two rivers. The dosage of the effluents required to kill 50% (LC50) and 90% (LC90) of the larvae varied significantly among stations. Lower values of LC50 and LC90 were observed in midges taken from downstream stations. Significant difference (p < 0.05) in the LC50 of the Chironomus species between the sampling stations of the rivers when exposed to different concentrations of industrial effluents was observed. hence the survival from exposure observation was found to be dosage dependent. The study concluded that Chironomus species are not very sensitive to pollutants; they can adapt to the prevailing environmental conditions and therefore reliable for biomonitoringl studies.