Nutrient uptake in Gracilaria corticata var. cylindrica with optimized AMPEP treatment under different nutrient conditions

The nutrient uptake, growth, and biochemical changes of the red seaweed Gracilaria corticata var. cylindrica, treated with Ascophyllum marine plant extract powder (AMPEP) (0.1 g L−1, 30 min) was, estimated after in vitro cultivation with inorganic synthetic chemical media for 14 days, to evaluate its potential for biofiltration in aquaculture systems. The time course nutrient uptake study demonstrated the impact of G. corticata var. cylindrica on ammonia, nitrate, and phosphate depletion in incubation media. The results indicated that AMPEP-treated seaweed influenced the depletion rate of all three nutrients, with maximum ammonia and nitrate depletion occurring after approximately 48 h and relatively stable phosphate levels over time (nutrient uptake rate). The maximum uptake of 270 μM g− 1 DW h− 1 of ammonium was observed, followed by nitrate (58.13 μM g− 1 DW h− 1) and phosphate (19.58 μM g− 1 DW h− 1). Seaweed fragments with 32 µg ml− 1 of phosphate showed a higher significant growth rate (2.41 ± 0.07% day− 1) than the control. The highest (1365.29 ± 78.61 µg g− 1) carbohydrate content was observed in 250 µg ml− 1 concentration of ammonia. The concentration of 128 µg ml− 1 of nitrate showed the highest (521.60 ± 50.5 µg g− 1) protein content. However, at 175 µg ml− 1 ammonia, the highest levels of R-phycocyanin (152.46 ± 28 µg g− 1) and R-phycoerythrin (237.19 ± 36.1 µg g− 1) were observed. Results show that the nutrient treatment positively affects G. corticata var. cylindrica growth and development and changes the biochemical composition, especially in carbohydrate, protein, and pigment concentration. G. corticata var. cylindrica has tremendous potential to be used in Integrated Multi-Trophic Aquaculture and reduce organic matter loading into the marine environment.