Unlocking synergies: Enhancing bioremediation, growth, and physiological responses of Penaeus vannamei co-cultured with seaweed

Seaweeds, an inorganic extractive species in the Integrated multi-trophic aquaculture (IMTA) system, offer the potential for mitigating coastal pollution and a source of nutrition aligning with Sustainable Development Goals. A co-culture strategy was hypothesized to address rising concerns over intensive shrimp farming, limited suitable seaweed cultivation areas, and production optimization. Initially, locally available seaweeds along the Maharashtra coast were screened, followed by co-culture with P. vannamei with selected seaweed to evaluate production performance and physiological responses in zero-water exchange system. The first four-week study was conducted in shrimp wastewater with six different seaweeds, where Gracilaria foliifera performed best with significant (p < 0.05) improvement in nutrient uptake efficiency (Total ammoniacal nitrogen- 64 %, Phosphate- 99.87 %, Nitrite-32 %, Nitrate-13 %) and yield (4.56 kg m⁻³), enhanced elemental profile, biochemical composition, and pigments. A further optimization study of G. foliifera in shrimp wastewater for 96 h identified the optimal stocking density of 1–3.5 gL⁻¹, based on nutrient uptake efficiency (TAN- 61 %, PO₄–72 %, NO₂–48 %, NO₃–27 %). In the second experiment, considering the highest uptake, G. foliifera stocking density was maintained at 3.5 gL⁻¹, and different stocking densities of P. vannamei (20, 40, 60, 80, 100 nos. m⁻²) were assessed with two controls, shrimp monoculture and Gracilaria monoculture. Results showed that co-culturing P. vannamei at 20 nos.m⁻² followed by 60 nos.m⁻² with G. foliifera at 3.5 gL⁻¹ yielded the highest mean weight gain, specific growth rate, and production with low feed conversion ratio, while also improving water quality. The co-culture system also led to lower stress enzyme levels, reduced serum glucose and cholesterol, and normal histological observations in the hepatopancreas compared to monoculture. This study suggests that the co-culture of P. vannamei at 60 nos.m⁻² with G. foliifera at 1–3.5 gL⁻¹ proved superior without compromising productivity and physiological responses over monoculture in a sustainable manner.