Effects of Nitrogen Source and Concentration on the Growth and Biochemical Composition of the Red Seaweed Grateloupia turuturu (Halymeniaceae, Rhodophyta)

Seaweeds, as biofilters that remediate seawater eutrophication, have been widely applied in integrated cultivations for both ecological and economic benefits. Although Grateloupia turuturu (Rhodophyta) is considered as a qualified species in integrated maricultivation, its growth and biochemical performance under different nitrogen conditions are still unknown. Here, we cultured G. turuturu under two nitrogen sources (nitrate and ammonium) at six concentrations (0, 25, 50, 100, 200, and 400 µM) to investigate its growth and nitrogenous compounds (total and inorganic nitrogen, soluble protein, amino acids, and pigments) as well as the allocation pattern of nitrogen storage pools. Our results showed that G. turuturu was well acclimated to high concentrations of both nitrogen sources, and algal age played an important role in the preference of nitrogen sources. Most of the biochemical compositions in G. turuturu increased significantly with the increased concentrations of nitrogen, except for the protein and nitrate contents. Protein and residual organic nitrogen (RON, mainly amino acids) were found to be the two main nitrogen storage pools in G. turuturu . Our study revealed that G. turuturu can produce more profitable compositions at high nitrogen concentrations, making it a profitably promising biofilter to remediate eutrophication.