Time-course nutrient uptake efficiency of intertidal red seaweeds in shrimp farm effluent: a sustainable bioremediation approach

Abstract Ammonium, phosphate, and nitrate are released into coastal waters through effluent discharge from shrimp aquaculture, the leading cause of eutrophication. These effluents also contribute to ecological degradation. This study evaluates the nutrient uptake performance of five intertidal rocky shore seaweed species, Sarconema filiforme , Gracilaria corticata , Scinaia carnosa , Gracilaria dura , and Acanthophora sp. , cultivated in shrimp farm effluent under controlled conditions. Colorimetric nutrient assays were used to evaluate absorption at time intervals of 0, 0.25, 0.50, 1, 2, 3, 4, 5, 6, 12, 24, 48, 72, and 96 h. The ability of all seaweed species to effectively absorb ammonium, phosphate, and nitrate from the shrimp farm effluent in less than 96 h demonstrated their potential for nutrient remediation. On the other hand, Acanthophora sp . exhibited a quicker nitrate removal pattern, reaching complete uptake in just 48 h, suggesting its adequate but short nitrate assimilation capacity. S. filiforme achieved the maximum nutrient removal efficiencies of 85.77 ± 5.27% phosphate (0.05 µM. g⁻¹ wet wt. h⁻¹), 100 ± 0% nitrate (1.18 ± 0.15 µM. g⁻¹ wet wt. h⁻¹), and 73.80 ± 7.968% ammonium (2.16 ± 0.35 µM. g⁻¹ wet wt. h⁻¹), but showed mortality in high ammonium conditions. Acanthophora sp. exhibited fast nitrate uptake and short-term survival, while G. corticata displayed superior durability with improved removal of nutrients. Among these three nutrients, seaweeds showed the highest absorption for nitrate than phosphate, and the least for ammonium, following the sequence: Nitrate > Phosphate > Ammonium. The study supports a sequential bioremediation strategy integrating multiple species based on uptake profiles and environmental tolerance, providing a sustainable alternative for nutrient reduction in shrimp farm wastewater. Graphical Abstract