The driving mechanisms of submarine groundwater discharge (SGD) in Sanya Bay in the northern South China Sea were investigated using a combination of time-series observation and modeling, as well as the influences of SGD on the carbonate system of a coastal coral reef. SGD flux, characterized by high variability on flood-ebb and spring-neap tidal cycles, was found to be mainly driven by tidal pumping. SGD posed more significant impacts on coastal water at the ebb phase during the spring tide (higher SGD flux and extended offshore reach of SGD impact), with nearshore water to be more heavily affected. Under the influence of SGD, the diurnal ranges of the carbonate variables observed in the coral reef system were 124 – 313 μmol kg⁻¹ for dissolved inorganic carbon, 29 – 101 μmol kg⁻¹ for total alkalinity, 179 – 717 μatm for partial pressure of CO₂, and 0.20 – 0.45 for pH. The variations of the CO₂ system were dominated by the enhanced SGD input during the spring tide, while biological metabolism of coral reef played a predominant role during the neap tide. The intensified SGD input resulted in higher diurnal variations of the carbonate variables, enhanced acidification, and oceanic CO₂ emission during the spring tide. The SGD-associated inorganic carbon flux is an additional stressor influencing coastal acidification in the context of rising atmospheric carbon dioxide.

中文翻译：

---

潮汐驱动的海底地下水排放及其对南海北部沿海珊瑚礁碳酸盐岩系统的影响

采用时序观测和建模相结合的方法，研究了南海北部三亚湾海底地下水排放（SGD）的驱动机制，以及SGD对沿海珊瑚礁碳酸盐岩系统的影响。发现 SGD 通量的特点是洪水 - 退潮和春季 - 小潮周期的高度可变性，主要由潮汐泵驱动。在大潮的退潮阶段，SGD 对沿海水域的影响更为显着（SGD 通量更高，SGD 影响的近海范围扩大），近岸水域受到的影响更大。下SGD的影响，在珊瑚礁系统观察到的变量碳酸盐的昼夜范围分别为124 - 313微摩尔千克^-1为溶解的无机碳，29 - 101微摩尔千克^-1对于总碱度，CO ₂分压为 179 – 717 μatm ，pH 值为 0.20 – 0.45。CO ₂系统的变化以大潮期间SGD输入的增加为主，而珊瑚礁的生物代谢在小潮期间起主导作用。强化的 SGD 输入导致大潮期间碳酸盐变量的日变化更大、酸化增强和海洋 CO ₂排放。在大气二氧化碳上升的背景下，与 SGD 相关的无机碳通量是影响沿海酸化的额外压力因素。