The effect of humic substances on the toxicity of aluminium to adult rainbow trout, Oncorhynchus mykiss (Walbaum)

Authors

  • H. E. Witters,

    Corresponding author
    1. Belgian Nuclear Research Centre, SCK/CEN, Radionuclide Metabolism Section, Boeretang 200, B-2400 Mol, Belgium
    2. University of Antwerp, Department of Biology, Universiteitsplein 1, B–2610 Wilrijk, Belgium
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  • S. Van Puymbroeck,

    1. Belgian Nuclear Research Centre, SCK/CEN, Radionuclide Metabolism Section, Boeretang 200, B-2400 Mol, Belgium
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  • J. H. D. Vangenechten,

    1. Belgian Nuclear Research Centre, SCK/CEN, Radionuclide Metabolism Section, Boeretang 200, B-2400 Mol, Belgium
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  • O. L. J. Vanderborght

    1. Belgian Nuclear Research Centre, SCK/CEN, Radionuclide Metabolism Section, Boeretang 200, B-2400 Mol, Belgium
    2. University of Antwerp, Department of Biology, Universiteitsplein 1, B–2610 Wilrijk, Belgium
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†To whom correspondence should be addressed at the Belgian Nuclear Research Centre.

Abstract

Some physiological parameters were measured in adult rainbow trout during a 10-day exposure to 180 μg Altotal l−1 in acid water (pH 4.7) with or without humic substances (10 mg l). The fish were acclimatized to pH 5.0 for 7 days prior to the experimental treatments.

Chemical analyses revealed that, in the presence of human substances, 74–80% of the A1 was organic bound, while in the absence of humic substances most of the Al(987percnt;) occurred in the inorganic form.

Al bound to humic substances (13–150 μg l−1) did not alter the plasma NaCl-concentration, nor the haematocrit value, of rainbow trout during an exposure period of 10 days. This contrasts with the high death rate obtained within 2–3 days when most of the A1 (175 μg l−1) was in the inorganic form. The lethality was accompanied by a 25% decrease in the plasmaconcentration of NaCl and a doubling of the haematocrit value. Bulk analysis revealed that when the metal was present in inorganic forms the total Al content of the gills (75 μg A1 g−1 wet weight) was 15 times higher than when it was present as bound to the humic substances. These experiments showed that the accumulation of A1 at the gills was accompanied by physiological disturbances, both being a function of the chemical speciation of Al.

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