Doctoral theses

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    Evaluation of the toxicity of some fertilizers on an animal model bioindicator of pollution ( earthworms). " Evalution de la toxicité de quelques engrais sur un modèle animal bioindicateur de pollution ( vers de terre)."
    (2024) Aouaichia Khaoula
    The present study applied the adult earthworm species Aporrectodeatrapezoides (Dugès, 1828) as a sentinel bioindicator for assessing the potential risks of ammonium sulfate (AS) and potassium nitrate (NK) fertilizers. Two complementary toxicity tests (lethal and sub-lethal) were conducted in order to determine : the 50 lethal concentration (LC) values of both fertilizers, growth rate, morphological aspect, total protein content, and enzymatic and non-enzymatic oxidative stress biomarkers, as well as the histological alterations in diverse body regions of worm. The lethality tests revealed significantly that the 50 LC values of both AS and NK fertilizers at 14 days (2698.67 and 4955.70 mg/kg of dry soil weight (d.s.w.)) are inferior to the 50 LC values at 7 days (4831.13 and 5530.43 mg/kg d.s.w.), respectively, and that AS fertilizer are more toxic to A. trapezoids than NK fertilizer. Indicates evidently strong toxicological effects at long exposure periods, even with low concentrations. Notably, earthworms exhibited a significant reduction in growth rate under different concentrations (of both AS and NK fertilizers) and exposure time-dependence. Severe morphological alterations were accentuated mainly with increasing concentrations of both AS and NK fertilizers. In addition, an induced depletion of total protein content instigates the activation of the detoxification system through a decrease in GSH levels, accompanied by an increase in GST and GPx activities, and an induction of CAT activity and MDA levels in A. trapezoides under different concentrations and time exposure dependence. Finally, sharp histological texture destruction was observed at different body parts of the worm (body wall, pharynx, digestive tract, and intestinal wall). The study highlights the strong relationship between concentrations and exposure time responses of such inorganic fertilizers and underscores the ability of A. trapezoides earthworm as a valuable biological control agent for soil toxicity. Decisively, this research contributes to the use of biomarkers in evaluating soil toxicity and the biological control of environmental risk assessment that associated with chemical fertilizers.