Estuarine and Coastal Sediments – Coupled Biogeochemical Cycling

Burdige, David J.

doi:10.1016/b978-0-12-374711-2.00511-8

Cited by 47 publications

(61 citation statements)

References 366 publications

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“…Sulfate reduction creates a TA / DIC ratio very close to 1 in the porewaters. This situation is very similar to Mangrove Lake sediments (Mackenzie et al, 1995) where depletion of sulfate is almost complete and DIC and TA concentrations build up to 40 mmol L −1 in the sediment porewaters, or to other coastal environments (Burdige, 2011;Antler et al, 2014). No other reaction in the anoxic zone has a TA / DIC production ratio near 1.…”

Section: Sulfate Reduction and Its Impact On Carbonate Chemistrymentioning

confidence: 48%

“…As demonstrated by Burdige (2011) and Burdige and Komada (2011), the interactions of all diagenetic pathways are hard to disentangle and do not provide clear evidence of changes in the DIC / SO 2− 4 ratio. Nonetheless, the value of the observed DIC / SO 2− 4 ratio (1.8 ± 0.1) points towards the dominance of sulfate reduction in the deeper layers of the sediment (below 10 cm depth).…”

Section: Sulfate Reduction and Its Impact On Carbonate Chemistrymentioning

confidence: 99%

“…Indeed, in organic rich sediments, sulfate reduction can account for the majority of OM mineralization (Gaillard et al, 1989;Jourabchi et al, 2005;Burdige, 2011;Fenschel et al, 2012). Following reaction R9, two units of DIC and TA are produced for one unit of sulfate consumed (Mucci et al, 2000;Krumins et al, 2013).…”

Section: Sulfate Reduction and Its Impact On Carbonate Chemistrymentioning

confidence: 99%

“…Sulfate reduction slightly decreases pH Soetaert et al, 2007), but nevertheless, it tends to enhance carbonate precipitation because of its coupling with precipitation of sulfide minerals from iron oxides (Gaillard et al, 1989;Mucci et al, 2000;Burdige, 2011). As an example, in sapropelic sediments from Mangrove Lake, Mackenzie et al (1995) reported a stable pH throughout the sulfatereduction zone and a buildup of supersaturation with respect to carbonate with depth.…”

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Carbonate chemistry in sediment porewaters of the Rhône River delta driven by early diagenesis (northwestern Mediterranean)

et al. 2016

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Abstract. The Rhône River is the largest source of terrestrial organic and inorganic carbon for the Mediterranean Sea. A large fraction of this terrestrial carbon is either buried or mineralized in the sediments close to the river mouth. This mineralization follows aerobic and anaerobic pathways, with a range of impacts on calcium carbonate precipitation and dissolution in the sediment near the sediment-water interface. This study focuses on the production of dissolved inorganic carbon (DIC) and total alkalinity (TA) by early diagenesis, consequential pH variations and the effect on calcium carbonate precipitation or dissolution. The sediment porewater chemistry was investigated along a transect from the Rhône River outlet to the continental shelf. TA and concentrations of DIC, SO 2− 4 and Ca 2+ were analyzed on bottom waters and extracted sediment porewaters, whereas pH and oxygen concentrations were measured in situ using microelectrodes. The average oxygen penetration depth into the sediment was 1.7 ± 0.4 mm close to the river mouth and 8.2 ± 2.6 mm in the continental shelf sediments, indicating intense respiration rates. Diffusive oxygen fluxes through the sediment-water interface ranged between 3 and 13 mmol O 2 m −2 d −1 . In the first 30 cm of the sediment, TA and DIC porewater concentrations increased with depth up to 48 mmol L −1 near the river outlet and up to 7 mmol L −1 on the shelf as a result of aerobic and anaerobic mineralization processes. Due to aerobic processes, at all stations pH decreased by 0.6 pH units in the oxic layer of the sediment accompanied by a decrease of the saturation state regarding calcium carbonate. In the anoxic layer of the sediments, sulfate reduction was the dominant mineralization process and was associated with an increase of porewater saturation state regarding calcium carbonate.Ultimately anoxic mineralization of organic matter caused calcium carbonate precipitation demonstrated by a large decrease in Ca 2+ concentration with depth in the sediment. Carbonate precipitation decreased in the offshore direction, together with the carbon turnover and sulfate consumption in the sediments. The large production of porewater alkalinity characterizes these sediments as an alkalinity source to the water column, which may increase the CO 2 buffering capacity of these coastal waters. Estuarine sediments should therefore receive more attention in future estimations of global carbon fluxes.

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Section: Sulfate Reduction and Its Impact On Carbonate Chemistrymentioning

confidence: 48%

Section: Sulfate Reduction and Its Impact On Carbonate Chemistrymentioning

confidence: 99%

Section: Sulfate Reduction and Its Impact On Carbonate Chemistrymentioning

confidence: 99%

mentioning

confidence: 99%

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Carbonate chemistry in sediment porewaters of the Rhône River delta driven by early diagenesis (northwestern Mediterranean)

et al. 2016

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“…Taxas de remineralização variam tanto espacial como temporalmente e são dependentes de inúmeros fatores, como a concentração de nutrientes e oxigênio da água de fundo, taxas de deposição, temperatura, redução de sulfato e bioturbação (Burdige, 2011). Deste modo, muitos estudos são conduzidos a partir de experimentos em laboratório, que podem ser extremamente vantajosos e satisfatórios, gerando resultados rápidos e permitindo os mais diversos tipos de manipulações e induções de tratamentos (Quintana, 2008).…”

Section: Introductionunclassified

Remineralização da matéria orgânica sedimentar em resposta à simulação de processos oceanográficos

Godoi¹

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Are mangroves drivers or buffers of coastal acidification? Insights from alkalinity and dissolved inorganic carbon export estimates across a latitudinal transect

Sippo

Maher

Tait

et al. 2016

Global Biogeochemical Cycles

176

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Mangrove forests are hot spots in the global carbon cycle, yet the fate for a majority of mangrove net primary production remains unaccounted for. The relative proportions of alkalinity and dissolved CO 2 [CO 2 *] within the dissolved inorganic carbon (DIC) exported from mangroves is unknown, and therefore, the effect of mangrove DIC exports on coastal acidification remains unconstrained. Here we measured dissolved inorganic carbon parameters over complete tidal and diel cycles in six pristine mangrove tidal creeks covering a 26°latitudinal gradient in Australia and calculated the exchange of DIC, alkalinity, and [CO 2 *] between mangroves and the coastal ocean. We found a mean DIC export of 59 mmol m À2 d À1 across the six systems, ranging from import of 97 mmol m À2 d À1 to an export of 85 mmol m À2 d À1 . If the Australian transect is representative of global mangroves, upscaling our estimates would result in global DIC exports of 3.6 ± 1.1 Tmol C yr À1 , which accounts for approximately one third of the previously unaccounted for mangrove carbon sink. Alkalinity exchange ranged between an import of 1.2 mmol m À2 d À1 and an export of 117 mmol m À2 d À1 with an estimated global export of 4.2 ± 1.3 Tmol yr À1 . A net import of free CO 2 was estimated (À11.4 ± 14.8 mmol m À2 d À1 ) and was equivalent to approximately one third of the air-water CO 2 flux (33.1 ± 6.3 mmol m À2 d À1 ). Overall, the effect of DIC and alkalinity exports created a measurable localized increase in coastal ocean pH. Therefore, mangroves may partially counteract coastal acidification in adjacent tropical waters.

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Estuarine and Coastal Sediments – Coupled Biogeochemical Cycling

Cited by 47 publications

References 366 publications

Carbonate chemistry in sediment porewaters of the Rhône River delta driven by early diagenesis (northwestern Mediterranean)

Carbonate chemistry in sediment porewaters of the Rhône River delta driven by early diagenesis (northwestern Mediterranean)

Remineralização da matéria orgânica sedimentar em resposta à simulação de processos oceanográficos

Are mangroves drivers or buffers of coastal acidification? Insights from alkalinity and dissolved inorganic carbon export estimates across a latitudinal transect

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