The impact of sedimentary alkalinity release on the water column CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; system in the North Sea

Brenner, Heiko; Braeckman, Ulrike; Guitton, M. Le; Meysman, Filip J. R.

doi:10.5194/bgd-12-12395-2015

Cited by 4 publications

(8 citation statements)

References 102 publications

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“…On annual basis, the A T residual in Ringkøbing Fjord before the regime shift was approximately 0.3–0.4 mmol kg −1 yr −1 (Figure b) corresponding to an average net areal flux of 1.6–2.1 mmol m −2 d −1 , similar to the estimate by Brenner et al () for the Southern North Sea. The conspicuous seasonal A T development in Ringkøbing Fjord thus appears to support substantial internal A T fluxes mediated by biogeochemical processes.…”

Section: Discussionsupporting

confidence: 83%

“…Using the basin characteristics (Table ), the A T increase in Ringkøbing Fjord from April to September corresponds to an average areal flux of approximately 7.5 mmol m −2 d −1 . In fact, measurements by Brenner et al () at numerous sites in the Southern North Sea revealed sediment to water A T fluxes in a range 0–21.4 mmol m −2 d −1 (mean: 6.6 mmol m −2 d −1 ). In a numerical experiment, including A T sources and sinks in both sediments and water column, Brenner et al () calculated a net A T generation in the water column of 2.4 mmol m −2 d −1 .…”

Section: Discussionmentioning

confidence: 97%

“…In fact, measurements by Brenner et al () at numerous sites in the Southern North Sea revealed sediment to water A T fluxes in a range 0–21.4 mmol m −2 d −1 (mean: 6.6 mmol m −2 d −1 ). In a numerical experiment, including A T sources and sinks in both sediments and water column, Brenner et al () calculated a net A T generation in the water column of 2.4 mmol m −2 d −1 . They identified the main A T sources as pelagic primary production and benthic CaCO 3 dissolution, denitrification, and sulfate reduction.…”

Section: Discussionmentioning

confidence: 97%

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Long‐Term and Seasonal Trends in Estuarine and Coastal Carbonate Systems

Carstensen

Chierici

Gustafsson

et al. 2018

Global Biogeochemical Cycles

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Coastal pH and total alkalinity are regulated by a diverse range of local processes superimposed on global trends of warming and ocean acidification, yet few studies have investigated the relative importance of different processes for coastal acidification. We describe long‐term (1972–2016) and seasonal trends in the carbonate system of three Danish coastal systems demonstrating that hydrological modification, changes in nutrient inputs from land, and presence/absence of calcifiers can drastically alter carbonate chemistry. Total alkalinity was mainly governed by conservative mixing of freshwater (0.73–5.17 mmol kg−1) with outer boundary concentrations (~2–2.4 mmol kg−1), modulated seasonally and spatially (~0.1–0.2 mmol kg−1) by calcifiers. Nitrate assimilation by primary production, denitrification, and sulfate reduction increased total alkalinity by almost 0.6 mmol kg−1 in the most eutrophic system during a period without calcifiers. Trends in pH ranged from −0.0088 year−1 to 0.021 year−1, the more extreme of these mainly driven by salinity changes in a sluice‐controlled lagoon. Temperature increased 0.05°C yr−1 across all three systems, which directly accounted for a pH decrease of 0.0008 year−1. Accounting for mixing, salinity, and temperature effects on dissociation and solubility constants, the resulting pH decline (0.0040 year−1) was about twice the ocean trend, emphasizing the effect of nutrient management on primary production and coastal acidification. Coastal pCO2 increased ~4 times more rapidly than ocean rates, enhancing CO2 emissions to the atmosphere. Indeed, coastal systems undergo more drastic changes than the ocean and coastal acidification trends are substantially enhanced from nutrient reductions to address coastal eutrophication.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 97%

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Long‐Term and Seasonal Trends in Estuarine and Coastal Carbonate Systems

Carstensen

Chierici

Gustafsson

et al. 2018

Global Biogeochemical Cycles

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“…Recent studies have pointed out that the alkalinity generation in coastal sediments may increase the capacity of the coastal ocean to act as a potential sink for atmospheric CO 2 (Thomas et al 2009;Faber et al 2012;Brenner et al 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Sedimentary alkalinity production can offset the effect of dissolved inorganic carbon production by respiration on the acidification of coastal waters, thus enhancing the uptake of atmospheric CO 2 (Hu and Cai 2011;Brenner et al 2016). For example, in M A N U S C R I P T…”

Section: Introductionmentioning

confidence: 99%

Carbon, iron and sulphur cycling in the sediments of a Mediterranean lagoon (Ghar El Melh, Tunisia)

Oueslati

Velde

Helali

et al. 2019

Estuarine, Coastal and Shelf Science

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Coastal lagoon sediments are important for the biogeochemical carbon cycle at the land-ocean transition, as they form hotspots for organic carbon burial, as well as potential sites for authigenic carbonate formation. Here, we employ an early diagenetic model to quantify the coupled redox cycling of carbon, iron and sulphur in the sediments of the shallow Ghar El Melh (GEM) lagoon (Tunisia). The model simulated depth profiles show a good correspondence with available pore water data (dissolved inorganic carbon, NH 4 + , total alkalinity, Ca 2+ , Fe 2+ and SO 4 2-) and solid phase data (organic matter, pyrite, calcium carbonate and iron (oxyhydr)oxides). This indicates that the model is able to capture the dominant processes influencing the sedimentary biogeochemical cycling. Our results show that sediment of the GEM lagoon is an efficient reactor for organic matter breakdown (burial efficiency < 10 %),with an important role for aerobic respiration (32 %) and sulphate reduction (61 %).Despite high rates of sulphate reduction, free sulphide does not accumulate in the pore water, due to a large terrestrial input of reactive iron oxides and the efficient sequestration of free sulphide into iron sulphide phases. High pyrite burial (2.2 mmol FeS 2 m -2 d -1 ) prevents the reoxidation of reduced sulphide, thus resulting in a low total oxygen uptake (4.7 mmol m -2 d -1 ) of the sediment and a relatively high oxygen penetration depth. The formation of pyrite also generates high amounts of alkalinity in the pore water, which stimulates authigenic carbonate precipitation (2.7 mmol m -2 d -1 )and leads to alkalinity release to the overlying water (3.4 mmol m -2 d -1 ). Model simulations with and without an N-cycle reveal a limited influence of nitrification and denitrification on the overall organic matter diagenesis. Overall, our study highlights the potential role of coastal lagoons for the global carbon and sulphur cycle, and their possible contribution to shelf alkalinity, which increases the buffering capacity of the coastal ocean for CO 2 uptake.

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Carbon sources in the North Sea evaluated by means of radium and stable carbon isotope tracers

et al. 2016

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A multitracer approach is applied to assess the impact of boundary fluxes (e.g., benthic input from sediments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the d 13 C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration.In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indicates the presence of an external carbon source, which is traced to the European continental coastline using naturally occurring radium isotopes ( 224 Ra and 228 Ra). 228 Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of metabolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e., unbuffered) release of metabolic DIC. Finally, longterm pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.

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The impact of sedimentary alkalinity release on the water column CO<sub>2</sub> system in the North Sea

Cited by 4 publications

References 102 publications

Long‐Term and Seasonal Trends in Estuarine and Coastal Carbonate Systems

Long‐Term and Seasonal Trends in Estuarine and Coastal Carbonate Systems

Carbon, iron and sulphur cycling in the sediments of a Mediterranean lagoon (Ghar El Melh, Tunisia)

Carbon sources in the North Sea evaluated by means of radium and stable carbon isotope tracers

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