Lead Dynamics in Saline Aquaponics: Tissue Accumulation in Litopenaeus vannamei and Sesuvium portulacastrum and Root-Associated Bacterial Communities

Abstract

Simple Summary Coastal communities in tropical regions may rely on groundwater containing trace concentrations of heavy metals, including lead (Pb). When this water is used for aquaculture, Pb can enter the production system and accumulate in farmed organisms. This study monitored an eight-week saline aquaponic system supplied with naturally Pb-enriched water and examined Pb concentrations in water, the salt-tolerant plant Sesuvium portulacastrum, and farmed white shrimp (Litopenaeus vannamei), together with root-associated bacterial communities. Dissolved Pb concentrations were, on average, 75% lower at the hydroponic outlet than at the sampled inlet. This difference represents retention by the aquaponic system as a whole and may involve plant uptake, sedimentation, biofilter media, pipe surfaces, and biofilms. Pb was detected in plant tissues, showing that S. portulacastrum participated in Pb retention, although its specific contribution could not be quantified. Shrimp accumulated Pb mainly in the cephalothorax and showed temporal variation in several physiological indicators. Root-associated bacterial communities also differed descriptively between aquaponic plants and dune reference plants. Because the study involved one aquaponic system without an uncontaminated control system, these observations cannot establish Pb-specific effects. Nevertheless, the combined assessment of water, plants, shrimp, and microbial communities provides an exploratory framework for monitoring metal dynamics in saline aquaponics.