Sandy seepage faces as bioactive nitrate reactors: Biogeochemistry, microbial ecology and metagenomics

Jiang, Shan; Jin, Jie; Wei, Yongjun; Wu, Ying; Zhang, Yixue; Rocha, Carlos; Ibánhez, J. Severino P.; Zhang, Guosen; Zhang, Jing

doi:10.1016/j.gsf.2022.101529

Cited by 8 publications

(1 citation statement)

References 91 publications

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“…It is difficult, if not impossible, to replicate the complicated and variable conditions of STEs, which are influenced by a range of abiotic and biotic factors (Russoniello et al., 2016; Slomp & Cappellen, 2004). In situ studies are highly sensitive, include small‐scale heterogeneities, do not isolate processes from other subsurface reactions, and hydraulic gradients which may impact reaction rates remain unchanged (Bohlke et al., 2006; Jiang et al., 2023). The in situ tracer method is complex but is likely the best available method for measuring rates in groundwater systems.…”

Section: Discussionmentioning

confidence: 99%

Nitrification in a Subterranean Estuary: An Ex Situ and In Situ Method Comparison Determines Nitrate Is Available for Discharge

Wilson,

Song,

Anderson

et al. 2024

JGR Biogeosciences

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Subterranean estuaries (STEs) form in the subsurface where fresh groundwater and seawater meet and mix. Subterranean estuaries support a variety of biogeochemical processes including those transforming nitrogen (N). Groundwater is often enriched with dissolved inorganic nitrogen (DIN), and transformations in the STE determine the fate of that DIN, which may be discharged to coastal waters. Nitrification oxidizes ammonium (NH4+) to nitrate, making DIN available for N removal via denitrification. We measured nitrification at an STE, in Virginia, USA using in situ and ex situ methods including conservative mixing models informed by in situ geochemical profiles, an in situ experiment with 15NH4+ tracer injection, and ex situ sediment slurry incubations with 15NH4+ tracer addition. All methods indicated nitrification in the STE, but the ex situ sediment slurries revealed higher rates than both the in situ tracr experiment and mixing model estimations. Nitrification rates ranged 55.0–183.16 μmol N m−2 d−1 based on mixing models, 94.2–225 μmol N m−2 d−1 in the in situ tracer experiment, and 36.6–109 μmol N m−2 d−1 slurry incubations. The in situ tracer experiment revealed higher rates and spatial variation not captured by the other methods. The geochemical complexity of the STE makes it difficult to replicate in situ conditions with incubations and calculations based on chemical profiles integrate over longer timescales, therefore, in situ approaches may best quantify transformation rates. Our data suggest that STE nitrification produces NO3−, altering the DIN pool discharged to overlying water via submarine groundwater discharge.

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Section: Discussionmentioning

confidence: 99%

Nitrification in a Subterranean Estuary: An Ex Situ and In Situ Method Comparison Determines Nitrate Is Available for Discharge

Wilson,

Song,

Anderson

et al. 2024

JGR Biogeosciences

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Transport and reactivity of nitrous oxide and methane in two contrasting subterranean estuaries

Calvo‐Martin,

de la Paz,

Álvarez‐Salgado

et al. 2024

Limnology & Oceanography

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Continental groundwaters are commonly enriched in nitrous oxide (N2O) and methane (CH4), which can discharge into the coast. The contribution of this diffuse source to coastal N2O and CH4 emissions largely depends on the biogeochemical processes of coastal aquifer exit zones, known as subterranean estuaries. Here, we study the role of subterranean estuaries in modulating N2O and CH4 exports toward the coast. The two studied subterranean estuaries are located at Panxón and Ladeira beaches (Ría de Vigo, NW Iberian Peninsula) and had opposite oxygenation at their interior. Groundwater‐borne N2O was detected in the oxygenated subterranean estuary of Panxón Beach, although denitrification attenuated N2O before porewater was discharged into the coast. An N2O hotspot was detected at about 50 cm depth in this subterranean estuary, characterized by the presence of nitrate under suboxic conditions. This N2O also seems to be consumed along the flow path before discharging into the coast. The anoxic subterranean estuary of Ladeira Beach completely removed groundwater‐borne N2O. Yet, nitrification within its suboxic upper saline plume produced and exported N2O toward the coast, hiding the role of this subterranean estuary as an N2O sink. The anoxic subterranean estuary exported CH4 toward the coast. This CH4 was not sourced by continental groundwater, hence it was produced in situ fuelled by the accumulation of organic matter within the beach. The suboxic upper saline plume in Ladeira Beach and the oxygenated subterranean estuary of Panxón Beach acted as CH4 sinks.

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Microbiota of a seepage face at the mouth of a subterranean estuary: diversity, distribution and substrate dependence

Wu,

Wei,

Ibánhez

et al. 2023

Acta Oceanol. Sin.

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Sandy seepage faces as bioactive nitrate reactors: Biogeochemistry, microbial ecology and metagenomics

Cited by 8 publications

References 91 publications

Nitrification in a Subterranean Estuary: An Ex Situ and In Situ Method Comparison Determines Nitrate Is Available for Discharge

Nitrification in a Subterranean Estuary: An Ex Situ and In Situ Method Comparison Determines Nitrate Is Available for Discharge

Transport and reactivity of nitrous oxide and methane in two contrasting subterranean estuaries

Microbiota of a seepage face at the mouth of a subterranean estuary: diversity, distribution and substrate dependence

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