Acute Toxicological Response of Daphnia and Moina to Hydrogen Peroxide

Hydrogen peroxide (${\mathrm{H}}_2{\mathrm{O}}_2$) is suggested to be an environmentally benign chemical that may be used for wastewater purification. A recent study on the application of ${\mathrm{H}}_2{\mathrm{O}}_2$ in a wastewater stabilization pond (WSP) showed that ${\mathrm{H}}_2{\mathrm{O}}_2$ is a promising method to decrease high amounts of potentially toxic cyanobacteria. However, WSPs are complex biological systems that require healthy bacterial, phytoplankton, and zooplankton communities for optimal performance. Therefore, if ${\mathrm{H}}_2{\mathrm{O}}_2$ is to be regularly used in WSPs, its effect on all components of a healthy WSP food web, including zooplankton, must be assessed. This study quantifies the acute toxicity of ${\mathrm{H}}_2{\mathrm{O}}_2$ to Moina and Daphnia, two zooplankton genera that are common in WSPs in Western Australia’s Mediterranean climate. The results indicate that Daphnia carinata is less susceptible to ${\mathrm{H}}_2{\mathrm{O}}_2$ than Moina sp., as mean survival time was significantly higher at concentrations $\ge 2\mathrm{mg}{\mathrm{H}}_2{\mathrm{O}}_2/\mathrm{L}$. Additionally, the $\mathrm{L}{\mathrm{C}}_{50}$ was $5.6\mathrm{mg}{\mathrm{H}}_2{\mathrm{O}}_2/\mathrm{L}$ in Daphnia and $2\mathrm{mg}{\mathrm{H}}_2{\mathrm{O}}_2/\mathrm{L}$ in Moina, whereas the no observed adverse effect concentration (NOAEC) was 3 and $1.5\mathrm{mg}{\mathrm{H}}_2{\mathrm{O}}_2/\mathrm{L}$ for Daphnia and Moina, respectively. These values are below ${\mathrm{H}}_2{\mathrm{O}}_2$ doses that effectively removed toxic cyanobacteria from WSPs, and therefore indicate the urgent need to critically assess the effect of ${\mathrm{H}}_2{\mathrm{O}}_2$ on biological communities during field trials to ensure continuous performance of WSPs.