ACUTE LETHAL TOXICITY TEST OF HYPOCHLORITE AGAINST POPULATION CELL DENSITY OF Nannochloropsis sp.

Abstract

This study aimed to determine the acute lethal concentration of hypochlorite causing 50% mortality of Nannochloropsis sp. cell population within a 2-hour exposure period (LC50-2 hours). The study employed a Completely Randomized Design (CRD) with five concentration levels (0, 7.5, 15, 22.5, and 30 ppm) and four replications. Mortality percentage data were analyzed using probit analysis. The results showed that increasing hypochlorite concentration was linearly associated with increasing cell mortality, yielding the probit regression equation y = 1.5657x + 2.2921 (R² = 0.9101). The resulting LC50-2 hours value was 53.64 ppm. This threshold value is expected to serve as a reference for determining safe application concentrations of calcium hypochlorite in mass culture of Nannochloropsis sp., as well as a basis for further research on its selective effectiveness against zooplankton contaminants.