Adaptation of Ulva lactuca in low-salinity and high-nutrient water environment and its synergistic microbial effect on inorganic nitrogen removal

作者：Chen, Jinxin; Wu, Changzheng; Wan, Jinquan^*; Wang, Yan; Zhu, Bin; Wang, Xuejian; Bi, Zhangqing

来源：Journal of Applied Phycology, 2024, 36(1): 513-525.

DOI：10.1007/s10811-023-03121-w

• Ulva lactuca
• Chlorophyceae
• Low-salinity adaptation
• High-nutrient
• Bioremediation
• Nitrogen removal

Excess inorganic nitrogen in offshore estuarine areas can adversely affect coastal water quality. To explore the bioremediation potential of Ulva lactuca in low-salinity and high-nutrient water, the dissolved inorganic nitrogen (DIN) removal under different low salinities (0, 0.5, 1.0, 1.5, 2.0% NaCl) and high nutrients was studied. Static culture experiments exhibited a maximum DIN removal efficiency of 73.74% with U. lactuca in the 1.0% salinity system. The differences in DIN removal efficiency at 1.0, 1.5 and 2.0% NaCl salinity were not significant (p > 0.05 and could reach above 65%. High-throughput sequencing, scanning electron microscopy (SEM) and excitation emission matrix (EEM) analysis demonstrated that the diversity of microorganisms decreased with increasing salinity with Proteobacteria and Bacteroidota the main phyla, revealing the synergistic effect of U. lactuca and microbes. Response surface curves showed that the conditions affecting DIN removal efficiency from high to low were salinity, density, and C/N ratio. By simulating the fluctuation of salinity and water level in the offshore estuarine environment, the efficient DIN removal was more than 60% and dissolved oxygen (DO) concentration was about 8 mg L-1 with U. lactuca at salinity above 1.0% NaCl. In conclusion, this study explored the DIN removal pattern of U. lactuca in different low-salinity and high-nutrient water environments, which is of great importance for the ecological restoration of estuarine and coastal environments.