Effect of increasing salinity on the toxicity of methidathion to freshwater rotifers (Philodina Acuticornis Odiosa)

Methidathion is used on fruit and vegetable crops and has been identified by regulators in Australia as potentially posing a risk to the environment. Further ecotoxicological data for methidathion are required to enable water quality trigger values to be derived for use in risk assessment. Rotifers are a dominant zooplankton species in many inland freshwater lakes in Australia; such lakes can also experience increased salinities. Acute toxicity tests (24-h) were conducted to determine the toxicity of methidathion to the freshwater rotifer Philodina acuticornis odiosa and to investigate the influence of increasing salinity on methidathion toxicity. Rotifers were found to be relatively tolerant to methidathion with a 24-h LC50 of 3.5 mg/L. Results also suggested that there are no interactive effects of salinity on methidathion toxicity.