Effect of Nutrient and Light Intensity on Nutrient Uptakes of Gracilaria manilaensis

Nutrient and light are two important environmental factors in seaweed growth. Gracilaria has high potential for uptake of nutrient in sea water. Ammonium (NH4 -N) and nitrate (NO3 −N) uptake rates under different concentrations of nitrogen (N) level separately for ammonium and nitrate with incubated phosphate 10:1, (20/2, 50/5, 120/12, 200/20, 300/30 and 500/50 μM), during 24 hour. Second part of experiment was done under different light intensities (30, 50, 100 and 150 μmol photons m s) counting single (50 μM of NH4 -N or NO3 −N) and phosphorus 5 μM) during 24 hour. Results showed that the most elevated nitrate uptake was assessed after 1h (9.029 μmol gFW h) under 300 μM concentration and phosphorus uptake rate demonstrated the most outstanding uptake rate in same time under 50 μM phosphorus (3.89 μM gFW 1 h). The highest uptake rate of ammonium was evaluated after 1h as (17.01 μM gFW h) under 500 μM concentration. While, phosphorus results showed highest uptake rate under 50 μM (5.80 μmol gFW h). Furthermore, in second part nutrient uptake rates revealed increasing trend with increasing light intensity. The maximum uptake of ammonium, nitrate and phosphate is 3.06, 1.97 and 0.39 μMl gFW h respectively under 150μmol photons m s in the first hour of experiment. Nitrate and phosphate absorption capacity highly correlated to light intensity conditions meanwhile, no significant effect on ammonium uptake rate collected. Nitrogen removal under different concentrations of nitrate and ammonium were strongly dependent on the concentrations of inorganic concentration N and P.