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Influence of growth conditions on the results obtained in algal toxicity tests

Authors

  • Philipp Mayer,

    Corresponding author
    1. Institute for Environmental Science and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
    Current affiliation:
    1. The current address of P. Mayer is Environmental Chemistry Group, Research Institute of Toxicology, Utrecht University, P.O. Box 80058, 3508 TB Utrecht, The Netherlands
    • Institute for Environmental Science and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
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  • Jesper Frickmann,

    1. Institute for Environmental Science and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
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  • Erik R. Christensen,

    1. Department of Civil Engineering, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin 53201, USA
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  • Niels Nyholm

    1. Institute for Environmental Science and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
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Abstract

The influence of test conditions on results from algal growth inhibition tests was investigated for the toxicants atrazine, 3,4-dichloroaniline, 3,5-dichlorophenol, and potassium dichromate. Emphasis was put on the following four main factors: light, temperature, nitrogen source, and pH. The green alga Selenastrum capricornutum was grown in batch cultures, and the toxic response was measured as reduction in average growth rate, relative to controls. Multifactor experiments were carried out to investigate the effects of the above four factors as well as the interactions between them: light intensity (44 and 198 μE/m2/s), temperature (16 and 26°C), nitrogen source (NHmath image and NOmath image), and pH of the medium (7.5 and 8.6). Within the data set generated, the highest and lowest median effective concentration estimate differed by a factor of 3.8. The sensitivity of the test system to 3,4-dichloroaniline, potassium dichromate, and 3,5-dichlorophenol was less under light limitation than under light saturation. Conversely, with the photosynthetic inhibitor atrazine a reduced sensitivity was found at high light intensity, which, however, was high enough to cause slight photoinhibition. The inhibitory response to the weak organic acid 3,5-dichlorophenol was less at the high than at the low pH level, which stems from the fact that neutral species of ionizable compounds are usually more toxic than charged species. No effect of the nitrogen source on inhibitory responses could be ascertained, and temperature influenced the results only indirectly by interacting with light (the saturation intensity increases with temperature). It is concluded that the light intensity in standardized algal toxicity tests could preferably be increased to achieve light-saturated photosynthesis as this may potentially reduce test result variability.

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