COMPARATIVE ANALYSIS OF ACUTE TOXICITY OF SODIUM HYPOCHLORITE ON GAMBUSIA HOLBROOKI (MOSQUITOFISH ) IN DIFFERENT EXPERIMENTAL SYSTEMS

The aim of this study is to determine the acute toxicity of sodium hypochlorite (NaClO), which has become a common pollutant in aquatic ecosystems, on the model organism Gambusia holbrooki and to comparatively analyze the effect of three fundamental experimental systems (Static, Renewal, and Flow-through) used in ecotoxicology on LC50 values. Of the study, G. holbrooki individuals obtained from inland waters of the Thrace Region were exposed to different concentrations of NaClO for 96 hours. Mortality data were evaluated using Probit Analysis with IBM SPSS Statistics (v.26.0). According to the research findings, the 96-hour LC50 values were determined as 0.804 ppm in the static system, 0.404 ppm in the flow-through system, and 0.342 ppm in the renewal system. The results indicate that sodium hypochlorite falls into the "Highly Toxic" category for G. holbrooki. Moreover, it was determined that the choice of experimental system statistically significantly alters toxicity data; the renewal system, where the chemical is constantly refreshed and organisms are exposed to manipulation stress, yielded the most sensitive results. This study highlights the importance of experimental design selection in risk assessment protocols.