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<p>Water pollution with heavy metals, particularly cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), and iron (Fe), represents a major challenge for sustainable aquaculture, particularly in freshwater ecosystems receiving anthropogenic discharges. This study evaluated the influences of different water sources and qualities on growth performance, physiological status, immune response, oxidative stress, and microbial load in Nile tilapia during a 90-day rearing phase. Fish (initial weight: 12.59 ± 0.14&#xa0;g) were reared under three treatments: clean freshwater without biofloc (control), contaminated lake water (LW), and lake water integrated with biofloc technology (BFT-LW: a microbial-based system that converts nitrogenous wastes into microbial biomass and sequesters contaminants within the floc matrix). Water quality analysis confirmed elevated heavy metal concentrations and microbial load in LW, while biofloc application significantly modified physicochemical characteristics and reduced metal availability. Fish reared in LW exhibited reduced growth performance, impaired feed efficiency, suppressed growth hormone levels, and elevated stress biomarkers. Additionally, these fish showed altered hematological and biochemical indices, increased oxidative damage, and higher intestinal pathogenic bacterial loads. In contrast, the BFT-LW treatment markedly improved growth parameters (specific growth rate restored to levels comparable with clean freshwater), restored endocrine and hematological balance, enhanced innate immune and antioxidant responses, and significantly reduced heavy metal accumulation in vital organs and edible muscle tissue by 19–82% across all measured metals and tissues relative to the LW group. Bioaccumulation factors further confirmed the reduced uptake efficiency of metals under biofloc conditions. Overall, the integration of biofloc technology effectively alleviated the adverse physiological and microbial impacts associated with heavy metal-contaminated lake water. The resulting fish health and productivity indicators were comparable to those observed under clean freshwater conditions, establishing biofloc technology as a practical and sustainable strategy for aquaculture in polluted environments.</p> Graphical Abstract <p></p>

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Biofloc technology mitigates heavy metal stress and improves growth, health, and microbial balance of Nile tilapia cultivated in contaminated lake water

  • 期刊论文

  • 发表日期：

    2026年5月25日

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  • Walied M. Fayed,
  • Ghada R. Sallam,
  • Tarek A. Srour,
  • Adel H. Elsenbawi,
  • Omneya Ibrahim,
  • Ahmed E. Sallam,
  • Akram Ismael Shehata,
  • Mohammed F. El Basuini

摘要

Water pollution with heavy metals, particularly cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), and iron (Fe), represents a major challenge for sustainable aquaculture, particularly in freshwater ecosystems receiving anthropogenic discharges. This study evaluated the influences of different water sources and qualities on growth performance, physiological status, immune response, oxidative stress, and microbial load in Nile tilapia during a 90-day rearing phase. Fish (initial weight: 12.59 ± 0.14 g) were reared under three treatments: clean freshwater without biofloc (control), contaminated lake water (LW), and lake water integrated with biofloc technology (BFT-LW: a microbial-based system that converts nitrogenous wastes into microbial biomass and sequesters contaminants within the floc matrix). Water quality analysis confirmed elevated heavy metal concentrations and microbial load in LW, while biofloc application significantly modified physicochemical characteristics and reduced metal availability. Fish reared in LW exhibited reduced growth performance, impaired feed efficiency, suppressed growth hormone levels, and elevated stress biomarkers. Additionally, these fish showed altered hematological and biochemical indices, increased oxidative damage, and higher intestinal pathogenic bacterial loads. In contrast, the BFT-LW treatment markedly improved growth parameters (specific growth rate restored to levels comparable with clean freshwater), restored endocrine and hematological balance, enhanced innate immune and antioxidant responses, and significantly reduced heavy metal accumulation in vital organs and edible muscle tissue by 19–82% across all measured metals and tissues relative to the LW group. Bioaccumulation factors further confirmed the reduced uptake efficiency of metals under biofloc conditions. Overall, the integration of biofloc technology effectively alleviated the adverse physiological and microbial impacts associated with heavy metal-contaminated lake water. The resulting fish health and productivity indicators were comparable to those observed under clean freshwater conditions, establishing biofloc technology as a practical and sustainable strategy for aquaculture in polluted environments.

Graphical Abstract