Acute toxicological effects of Z-germicide on the aquatic beetle Orectogyrus bedeli

Abstract

Z-germicide, a phenolic disinfectant released into aquatic environments through industrial, agricultural, and domestic effluents, poses significant ecological risks. Although its toxicity to vertebrates is relatively well studied, little is known about its effects on aquatic insects that perform vital ecological functions. This study investigated the acute toxicity of Z-germicide on the whirligig beetle Orectogyrus bedeli Regimbart, 1884, by determining median lethal concentrations (LC₅₀) over different exposure periods. Laboratory bioassays were conducted at 20–22 °C, where beetles were exposed to graded concentrations of Z-germicide. Mortality was recorded at 24, 48, 72, and 96 hours, and LC₅₀ values were calculated using probit analysis. Water quality parameters, including dissolved oxygen, pH, conductivity, and total dissolved solids, were also measured. Results showed declining LC₅₀ values with increasing exposure time: 47.846 mg/L at 24 hours, 36.7891 mg/L at 48 hours, 8.670 mg/L at 72 hours, and 7.769 mg/L at 96 hours. Mortality followed a clear concentration and time-dependent trend. Conductivity and total dissolved solids increased significantly, while dissolved oxygen and pH remained relatively stable. These findings demonstrate the acute toxicity of Z-germicide to O. bedeli and highlight the ecological risks posed by phenolic pollutants. Effective pollution control and wastewater management are essential to protect aquatic biodiversity.