Sodium Chloride in Aquaculture: A Double-Edged Sword in Achieving SDG2, SDG3 and SDG14

Objective: This study aimed to investigate the genotoxic impact of sodium chloride (NaCl) on Oreochromis niloticus (Nile Tilapia), a globally significant aquaculture species. Specifically, it focused on DNA damage induced by NaCl concentrations substantially below the standard recommended range of 4–8 g/L, using the comet assay as a molecular biomarker. Theoretical Framework: Rooted in ecotoxicology and molecular biology, the study explores how commonly used aquaculture additives like NaCl may affect fish health at the cellular level. By integrating principles from both disciplines, the research examines the intersection of environmental exposure and genetic integrity, with implications for aquaculture sustainability and fish welfare. This aligns with global goals such as SDG 2 (Zero Hunger), SDG 3 (Good Health and Well-being) and SDG 14 (Life Below Water) emphasizing the role of responsible aquaculture practices. Method: Experimental groups of Nile Tilapia were exposed to two NaCl concentrations: 0.8 g/L (Low, L) and 1.6 g/L (High, H), over durations of 10 and 30 days. A control group was maintained in NaCl-free water. Blood samples were collected post-exposure, and single-cell gel electrophoresis (comet assay) was employed to detect DNA strand breaks. Comet parameters such as comet length and tail length were quantified using image analysis software to assess the extent of DNA damage. Results and Discussion: The results revealed a clear dose- and time-dependent increase in DNA damage. After 30 days at H levels of (1.6 g/L) NaCl, comet lengths averaged 44.5 px, significantly higher than the 29.78 px recorded in controls. Correspondingly, tail length increased from 3.01 px (control) to 10.6 px. At L levels of (0.8 g/L) NaCl for 30 days, comet lengths averaged 38.5 px, with tail length rising to 5.1 px. These findings indicate that even sub-recommended NaCl levels can induce significant genotoxic stress in O. niloticus, challenging its perceived resilience to salinity. Research Implications: Given the widespread use of salt in aquaculture for health management and stress mitigation, these findings call for a critical reassessment of NaCl application protocols. Understanding sub-lethal molecular effects is essential for informed decision-making in sustainable aquaculture practices, particularly in regions dependent on tilapia farming for food and livelihood security. Originality/Value: This study is among the few to demonstrate that NaCl, though traditionally considered a benign and beneficial additive, can act as a DNA-damaging agent in fish under chronic exposure, even at low concentrations. By highlighting genotoxic risks in a key aquaculture species, it contributes original insights into aquaculture toxicology and prompts a paradigm shift in the evaluation of routine inputs.