Coastal Acidification Induced by Tidal-Driven Submarine Groundwater Discharge in a Coastal Coral Reef System

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• 作者：Guizhi Wang ; Wenping Jing ; Shuling Wang ; Yi Xu ; Zhangyong Wang ; Zhouling Zhang ; Quanlong Li ; Minhan Dai
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：November 18, 2014
• 年：2014
• 卷：48
• 期：22
• 页码：13069-13075
• 全文大小：396K
• ISSN：1520-5851

文摘

We identified a barely noticed contributor, submarine groundwater discharge (SGD), to acidification of a coastal fringing reef system in Sanya Bay in the South China Sea based on time-series observations of Ra isotopes and carbonate system parameters. This coastal system was characterized by strong diel changes throughout the spring to neap tidal cycle of dissolved inorganic carbon (DIC), total alkalinity, partial pressure of CO₂ (pCO₂) and pH, in the ranges of 1851鈥?131 渭mol kg^鈥?, 2182鈥?271 渭mol kg^鈥?, 290鈥?88 渭atm and 7.72鈥?.15, respectively. Interestingly, the diurnal amplitudes of these parameters decreased from spring to neap tides, governed by both tidal pumping and biological activities. In ebb stages during the spring tide, we observed the lowest salinities along with the highest DIC, pCO₂ and Ra isotopes, and the lowest pH and aragonite saturation state. These observations were consistent with a concurrent SGD rate up to 25 and 44 cm d^鈥?, quantified using Darcy鈥檚 law and ²²⁶Ra, during the spring tide ebb, but negligible at flood tides. Such tidal-driven SGD of low pH waters is another significant contributor to coastal acidification, posing additional stress on coastal coral systems, which would be even more susceptible in future scenarios under higher atmospheric CO₂.