Integrated response to lead in saline aquaponics: plant-based remediation, microbial community shifts, and shrimp health

This study aimed to evaluate the multiscale biological responses to subchronic lead (Pb) exposure in a saline aquaponic system, using Sesuvium portulacastrum and Litopenaeus vannamei as model organisms. Physiological, biochemical, and microbiological indicators were assessed to characterize the impacts of dissolved Pb. S. portulacastrum demonstrated high Pb retention efficiency, exceeding 90% and achieving complete removal in certain weeks. However, retention fluctuated over time, modulated by nutrient dynamics, especially ammonium and phosphorus levels, suggesting ionic competition and phosphate precipitation as factors influencing metal bioavailability. Pb accumulated in all plant tissues, with patterns indicating active translocation from roots to aerial parts, and triggered a complex antioxidant response, characterized by dynamic changes in peroxidase and catalase activity. In L. vannamei , Pb bioaccumulated predominantly in the cephalothorax, causing metabolic disruptions, including elevated hemolymph protein and lipid levels, alongside marked immunosuppression. Reductions in hemocyte counts, lysozyme activity, and NBT reduction confirmed compromised immune and oxidative function, while catalase activity increased as a potential compensatory mechanism. Rhizospheric microbiota of Pb-exposed plants exhibited significant structural shifts, with increased alpha diversity and taxonomic enrichment of metal-tolerant genera such as Neptunomonas , Ferrimonas , and Arcobacter . These genera were strongly correlated with physiological and enzymatic stress indicators, supporting their role as functional microbial biomarkers of Pb exposure. Our findings highlight the multidimensional effects of lead in aquaponics, impacting plant physiology, shrimp health, and microbial ecology. This integrated evaluation provides a robust framework for microbiome-assisted phytoremediation strategies and the development of more resilient, metal-tolerant aquaponic systems.