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Laboratory cultures of Daphnia magna were maintained in hard well water and fed one of five different diets. Algal diets, trout chow diets, and diets combining algae and trout chow were evaluated.
The acute toxicity (48-h LC50) of C11.8 LAS (linear alkylbenzene sulfonate) to D. magna reared on the five different diets ranged between 3.6 and 4.7 mg/L. For daphnids that were fed during the acute test, the LC50s ranged between 4.4 and 8.1 mg/LLAS. The addition of food to the acute test generally increased the LC50.
Diet had a statistically significant effect on the sensitivity of D. magna to the chronic toxicity of LAS. Chronic no-observed effect concentrations (NOECs) varied about three-fold (1.2 to 3.2 mg/L) and 21-day LC50s about two-fold (2.2 to 4.7 mg/L) for daphnids fed the five diets. Survival was generally the most sensitive indicator of chronic effects. Food concentration also had a significant effect on the response of D. magna to the chronic effects of LAS. Daphnia cultures receiving lower concentrations of food were less sensitive to LAS than Daphnia cultures receiving higher food concentrations.
Diet had at most a three-fold effect on the results of Daphnia toxicity tests. A three-fold variability can be expected in Daphnia toxicity tests themselves. Therefore use of any of the diets in this study should not affect the utility of the test results in assessing the environmental effects of detergent chemicals such as LAS.
Daphnia, diet, nutrition, surfactant, acute, chronic
Aquatic Toxicologist, The Procter & Gamble Company, Ivorydale Technical Center, Cincinnati, Ohio