Submarine Groundwater Discharge in the Northern Bohai Sea, China: Implications for Coastal Carbon Budgets and Buffering Capacity

Abstract

Submarine groundwater discharge (SGD) has been widely recognized as an important source of dissolved nutrients in coastal waters and affects nutrient biogeochemistry. In contrast, little information is available on SGD impacts on coastal carbon budgets. Here, we assessed the SGD and associated carbon (dissolved inorganic carbon [DIC] and total alkalinity [TA]) fluxes in Liaodong Bay (the largest bay of the Bohai Sea, China) and discussed their border implications for coastal DIC budget and buffering capacity. Based on 223Ra and 228Ra mass balance models, the SGD flux was estimated to be (0.92–1.43) × 109 m3 d−1. SGD was the largest contributor of DIC, accounting for 55%–77% of the total DIC sources. The low ratio (<1) of SGD‐derived TA to DIC fluxes and negative correlation between radium isotopes and pH in seawater implied that SGD would potentially reduce seawater pH in Liaodong Bay. Combining the groundwater carbon data in Liaodong Bay with literature data, we found that the SGD‐derived DIC flux off China was 4–9 times greater than those from rivers. By analyzing the TA/DIC ratios in groundwater along the Chinese coast and related carbon fluxes, SGD was thought to partially reduce the CO2 buffer capacity in receiving seawater. These results obtained at the bay scale and national scale suggest that SGD is a significant component of carbon budget and may play a critical role in modulating coastal buffering capacity and atmospheric CO2 sequestration.

Submarine Groundwater Discharge Strengthens Acidification in the Coastal Semi‐Closed Bays

“…After reviewing the carbonate compositions in SGD fluxes worldwide, DIC/TA >1 was found in most SGD studies indicating the great potential for SGD to strengthen the acidification process in coastal seawater (Y. Liu et al., 2021). The same conclusion is obtained from a study in the northern Bohai Sea, China (Zhang et al., 2022). In addition to the implications, some direct observations also confirmed the abovementioned conclusion.…”

Small Muddy Paleochannels and Implications for Submarine Groundwater Discharge near Charleston, South Carolina, USA

“…Also, paleochannels may act as pathways for saltwater intrusion into these aquifers. The geochemical reactions and salinization of aquifers in general are key to their availability as a resource [19][20][21][22][23][24][25][26][27][28][29]. Offshore groundwater may become important as coastal development continues and sea levels rise [30,31].…”

Impact of connected conduit on pumping-induced seawater intrusion in a coastal karst aquifer

“…In coastal regions, interactions of seawater and freshwater bring about unique groundwater environment, numerous endeavors have investigated chemical releasing and accumulations, biological environmental problems, and different coastal carbon budgets (e.g. Luo et al, 2022;Xiao et al, 2022;Zhang et al, 2022;Wang et al, 2023). Furthermore, in coastal karst aquifers, the seawater-freshwater interactions may be amplified since the existence of interconnected conduit systems (Arthur et al, 2007;Fleury et al, 2007).…”