Carbon dynamics driven by seawater recirculation and groundwater discharge along a forest-dune-beach continuum of a high-energy meso-macro-tidal sandy coast

Charbonnier, Céline; Anschutz, Pierre; Abril, Gwénaël; Mucci, Alfonso; Deirmendjian, Loris; Poirier, Dominique; Bujan, Stéphane; Lécroart, Pascal

doi:10.1016/j.gca.2021.10.021

Cited by 10 publications

(7 citation statements)

References 113 publications

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“…A recent study provided insight into the implications of the TA/DIC ratio in external water inputs as an indicator for seawater pH variations (Liu et al., 2021). If the TA/DIC ratio in SGD is greater than 1, SGD increases the CO 2 buffer capacity of the ocean against the decline of seawater pH, otherwise SGD serves as a driver of ocean acidification (Charbonnier et al., 2022).…”

Section: Resultsmentioning

confidence: 99%

“…SGD with low TA/DIC ratios has the potential to reduce the pH and buffering capacity of coastal seawater (Davis et al., 2020; Liu et al., 2021). In contrast, SGD with high TA/DIC ratios would partially facilitate the atmospheric CO 2 sequestration, which represents a positive impact on increasing regional carbon sinks (Charbonnier et al., 2022). Thus aquatic CO 2 emissions may be mitigated or enhanced by SGD with important but easily overlooked implications on regional and global marine carbon cycling.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2022

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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

et al. 2022

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“…TA/DIC>1; Lee and Kim (2015)). More recently, Charbonnier et al (2022) reported strong aerobic remineralisation along the groundwater pathway of the high-energy, intertidal sandy sediment at Truc-Vert, SW France. Because of the active CO 2 degassing along the beach, the TA/DIC evolves above 1 and discharge increased the buffering capacity of the coastal seawater (Charbonnier et al, 2022).…”

Section: Introductionmentioning

confidence: 98%

“…More recently, Charbonnier et al (2022) reported strong aerobic remineralisation along the groundwater pathway of the high-energy, intertidal sandy sediment at Truc-Vert, SW France. Because of the active CO 2 degassing along the beach, the TA/DIC evolves above 1 and discharge increased the buffering capacity of the coastal seawater (Charbonnier et al, 2022). These contrasting results highlight the complexity of the behaviour of carbonate system parameters in STE and the necessity of sitespecific scale studies to characterize and quantify SGD-derived fluxes of DIC and alkalinity.…”

Section: Introductionmentioning

confidence: 98%

Production and fluxes of inorganic carbon and alkalinity in a subarctic subterranean estuary

Chaillou,

Tommi-Morin,

Mucci

2024

Front. Mar. Sci.

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In this study, we focus on the biogeochemical processes that produce both dissolved inorganic carbon (DIC) and total alkalinity (TA) along a subarctic subterranean estuary (STE) located in the Gulf of St. Lawrence (Magdalen Island, Qc, Canada) in order to evaluate the DIC and TA fluxes as well as the buffering capacity of the exported groundwater to coastal waters. DIC and TA do not behave conservatively during mixing along the groundwater flow path and this implies the occurrence of internal redox reactions that control both their production and consumption. In addition, we show that the origin and composition of the organic carbon within the system alter the carbonate parameters by generating low pH conditions (5.9 - 7.2) and contributing to non-carbonate alkalinity (NCA) that accounts for more than 30% of TA. Whereas iron cycling plays a key role in the production of DIC in the fresh and low-salinity groundwaters, the precipitation of sulfide minerals neutralize the acidity produced by the metabolically produced CO2, in the saline groundwater where sulfate is available. The STE pCO2, computed from the DIC-pHNBS pair ranged from a few ppm to 16000 ppm that results in a CO2 evasion rate of up to 310 mol m−2d−1 to the atmosphere. Based on Darcy flow and the mean concentrations of DIC and carbonate alkalinity (Ac = TA - NCA) in the discharge zone, fluxes derived from submarine groundwater discharge were estimated at 1.43 and 0.70 mol m−2d−1 for DIC and Ac, respectively. Despite a major part of the metabolic CO2 being lost along the groundwater flow path, the SGD-derived DIC flux was still greater than the Ac flux, implying that groundwater discharge reduces the buffering capacity of the receiving coastal waters. This site-specific scale study demonstrates the importance of diagenetic reactions and organic matter remineralization processes on carbonate system parameters in STE. Our results highlight that subarctic STEs could be hot spots of CO2 evasion and a source of acidification to coastal waters that should be considered in carbon budgets.

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“…Coastal aquifers, influenced by both terrestrial and marine factors, are among the most active and complex areas of solute circulation and energy exchange on earth (Jiao & Post, 2019; Ward et al., 2020). In coastal aquifers, the interactions between terrestrial fresh groundwater and coastal seawater triggers (bio)geochemical reactions, which significantly alter the concentrations and compositions of solutes (e.g., metals, nutrients, and organics) and their associated discharge from aquifers to the ocean (Charbonnier et al., 2022; Kong et al., 2021; Mohanty & Rao, 2019; Otani et al., 2010; Schutte et al., 2019). Dissolved trace metals only account for a small portion of the chemical composition in groundwater, but they represent the ecotoxicologically relevant fraction of contaminants in the environment (Castaño‐Sánchez et al., 2020; Parelho et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

Seawater–Groundwater Interaction Governs Trace Metal Zonation in a Coastal Sandy Aquifer

Wang,

Guo

et al. 2023

Water Resources Research

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Trace metals in the groundwater of coastal sandy aquifers significantly influence the coastal ecosystem, yet the spatiotemporal controls of these metals remain unclear. In this paper, we comprehensively revealed the distribution patterns, key controlling factors, potential ecological risks, and fluxes to the ocean of groundwater trace metals (As, Ba, Cr, Cd, Fe, Mn, Pb, and Zn) in a coastal deep sandy aquifer. The results showed a clear zonation of trace metals in the groundwater in relation to the mixing extent between seawater and terrestrial freshwater. The freshwater zone exhibited a relatively low concentration of trace metals, whereas the freshwater‐seawater transition zone showed a substantial quantity of dissolved Fe, Mn, As, and Ba. Seawater‐groundwater interactions significantly affected the Fe, Mn, As, and Ba concentrations through redox potential and pH gradients. The tide‐driven saline water zone was vulnerable to oceanic environments and anthropogenic activities, resulting in the enrichment of trace metals such as Zn and Cd. Driven by recirculated submarine groundwater discharge (SGD), the concentrations of trace metals in the density‐driven saline circulation zone were found to be higher than those in the surrounding areas. The ecological risk index suggested that the freshwater‐seawater transition zone posted the highest ecological risks. Trace metal fluxes (i.e., Fe, Mn, and As) via SGD significantly contributed to the total input into the sea, which may have potential impacts on the coastal environments. Our study highlighted the importance of seawater‐groundwater interactions on trace element cycling in coastal sandy aquifers.This article is protected by copyright. All rights reserved.

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Carbon dynamics driven by seawater recirculation and groundwater discharge along a forest-dune-beach continuum of a high-energy meso-macro-tidal sandy coast

Cited by 10 publications

References 113 publications

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

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

Production and fluxes of inorganic carbon and alkalinity in a subarctic subterranean estuary

Seawater–Groundwater Interaction Governs Trace Metal Zonation in a Coastal Sandy Aquifer

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