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Toxicity to aquatic plants other than algae

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Two aquatic plant (other than algae) studies were conducted. In the first study (Maki 1981), the long term toxicity of C11.6LAS to the aquatic plant (Elodea canadensis) was determined in a 28 day model ecosystem test. The nominal test concentrations were 0.5, 1.0, 2.0, and 4.0 mg/L, and were confirmed by analytical measurements.Growth inhibition was not observed even at highest tested concentration (4 mg/L). Growth throughout the exposure period approximately doubled the initial biomass of the vegetative shoots used at the start of the exposure. Hence, the NOEC was found to be >4 mg/L. The data are for C11.6 LAS and no normalization is required.

In the second study (Bishop and Perry 1981; Bishop 1980; van de Plassche et al 1999), the duckweed, Lemna minor, was exposed to C11.8LAS. Endpoints included frond count, dry weight, growth rate, and root length after a 7 day exposure period in a flow through study. The measured test concentrations were 0, 2.1, 3.8, 8, 17 and 34 mg/L. The resultant EC10 value, based on frond number, was 0.21 mg/L. The EC50 value, also based on frond number, was 2.30 mg/L C11.8LAS. Normalizing the EC10 of 0.21 mg/L to C11.6LAS results in a final value of 0.30 mg/L.

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Additional information

In general, algae were not affected by C12LAS or increased in density, particularly blue-green algae, and autotrophic activity increased with increasing C12 LAS. In contrast, some invertebrates declined in density at concentrations >0.293 mg/L, as a result of increasing drift from the shock of the initial dose or from long-term toxicity and habitat changes. Microbes acclimated to mineralizing C12 LAS. Overall, the heterotrophic periphyton community remained robust and did not change their food (amino acid) uptake rate.