This acute toxicity test with the water flea Daphnia magna is based on counting the number of immobilized organisms after 24 and 48 h of exposure to a series of dilutions of a water sample.
The purpose of the test is to measure and quantify the acute toxicity of the sampled water for this organism.
The effects are reported in terms of EC50 for immobilization. Eventually, also NOEC and LOEC are reported.
This kind of acute toxicity tests on water organisms are complementary to chemical analyses and organic screenings, because they give the overall effect of the mix of pollutants, present in the water sample. This combined effect is not always predictable, even when toxicity data on all the compounds in the sample would be available. Compounds can either inhibit or reinforce each other’s toxicity.It is particularly useful to perform the test on effluents that are discharged in rivers and channels.
The test is performed in two steps:
- A range finding test, by making log 10 dilutions.
- The final test with more refined dilutions within the effect-range
Four replicas of all dilutions are tested.
The test is performed according to ISO 6341 using a standardized test kit with built-in quality control.