Oxygen microprofiles measured in situ in deep ocean sediments

Reimers, Clare E.; Fischer, Kathleen M.; Merewether, Ray; Smith, Kenneth L.; Jahnke, Richard A.

doi:10.1038/320741a0

Cited by 143 publications

(51 citation statements)

References 14 publications

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“…[45] The combination of water column nutrient concentration and nitrate isotope data with in situ estimates of benthic nitrate flux provides new constraints on the nitrate [Reimers et al, 1986[Reimers et al, , 1992 [46] Water column nitrate integrates over large spatial and temporal scales and thus provides a robust measure of the mean basin-wide rate of sedimentary denitrification. On the basis of the distribution of N* in the water column and using an average water residence time of 50 years, we calculate that the average sedimentary denitrification below 2000 m water depth is 230 mmol m À2 d À1 .…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

Origin of the deep Bering Sea nitrate deficit: Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes

Lehmann¹,

Sigman

McCorkle

et al. 2005

Global Biogeochemical Cycles

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[1] On the basis of the normalization to phosphate, a significant amount of nitrate is missing from the deep Bering Sea (BS). Benthic denitrification has been suggested previously to be the dominant cause for the BS nitrate deficit. We measured water column nitrate 15 N/ 14 N and 18 O/ 16 O as integrative tracers of microbial denitrification, together with pore water-derived benthic nitrate fluxes in the deep BS basin, in order to gain new constraints on the mechanism of fixed nitrogen loss in the BS. The lack of any nitrate isotope enrichment into the deep part of the BS supports the benthic denitrification hypothesis. On the basis of the nitrate deficit in the water column with respect to the adjacent North Pacific and a radiocarbon-derived ventilation age of $50 years, we calculate an average deep BS (>2000 m water depth) sedimentary denitrification rate of $230 mmol N m À2 d À1 (or 1.27 Tg N yr À1 ), more than 3 times higher than high-end estimates of the average global sedimentary denitrification rate for the same depth interval. Pore water-derived estimates of benthic denitrification were variable, and uncertainties in estimates were large. A very high denitrification rate measured from the base of the steep northern slope of the basin suggests that the elevated average sedimentary denitrification rate of the deep Bering calculated from the nitrate deficit is driven by organic matter supply to the base of the continental slope, owing to a combination of high primary productivity in the surface waters along the shelf break and efficient down-slope sediment focusing along the steep continental slopes that characterize the BS.

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Section: Summary and Concluding Remarksmentioning

confidence: 99%

Origin of the deep Bering Sea nitrate deficit: Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes

Lehmann¹,

Sigman

McCorkle

et al. 2005

Global Biogeochemical Cycles

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“…In the analysis of the burial efficiency and OET of organic carbon, we include an additional, shallow-water (20 m) site. The oxygen penetration depths, L O2 , imposed at the 20, 200, 1000 and 4000 m water depth sites are 0.1, 0.3, 2.0 and 7.5 cm, respectively [e.g., Glud et al, 1994Glud et al, , 1998Gundersen and Jørgensen, 1990;Reimers et al, 1986].…”

Section: Applicationsmentioning

confidence: 99%

Particle age distributions and O₂ exposure times: Timescales in bioturbated sediments

Meile

Cappellen

2005

Global Biogeochemical Cycles

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[1] A stochastic particle tracking approach is used to compute particulate age distributions and oxygen exposure times (OETs) in bioturbated marine sediments. Simulations representative of abyssal plain, continental slope, and continental shelf sediments indicate that within the mixed zone, the variability in particle age is of the same order of magnitude as the average age itself. This spreading of particle age by bioturbation complicates the interpretation of sedimentary archives. The results further show that average and median ages of particle-bound constituents undergoing decay during early diagenesis deviate from those of inert tracers. Similarly, OETs depend on the biological mixing and biogeochemical reactivity of particulate constituents. Hence ratios of the O 2 penetration depth (L O2 ) and the linear sedimentation rate (w) may not offer reliable measures of actual OETs. Taking into account biodiffusional particle mixing and preferential degradation of organic matter under oxygenated conditions, the stochastic model predicts a global inverse relationship between the burial efficiency and the OET of organic carbon in ocean sediments. The relationship, however, differs significantly from that proposed by Hartnett et al. (1998), who used O 2 penetration depths divided by linear sedimentation rates (L O2 /w) to estimate OETs.Citation: Meile, C., and P. Van Cappellen (2005), Particle age distributions and O 2 exposure times: Timescales in bioturbated sediments, Global Biogeochem. Cycles, 19, GB3013,

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“…While laboratory-based investigations can provide valuable insight on diagenetic processes, measurements of benthic solute exchange using cores and microcosms can be compromised by disturbances during sediment recovery and challenges in re-establishing natural environmental conditions in the laboratory. However, while there for some time has been considerable awareness on the necessity of in situ investigation for quantifying microbial processing in deep-sea sediments (Reimers et al 1986;Jahnke et al 1990;Glud et al 1994;Smith et al 1997) only more recently has the requirement for in situ investigations of coastal sediments been acknowledged (Jahnke and Jahnke 2008;Toussaint et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Benthic Carbon Mineralization and Nutrient Turnover in a Scottish Sea Loch: An Integrative In Situ Study

et al. 2016

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Based on in situ microprofiles, chamber incubations and eddy covariance measurements, we investigated the benthic carbon mineralization and nutrient regeneration in a *65-m-deep sedimentation basin of Loch Etive, UK. The sediment hosted a considerable amount of infauna that was dominated by the brittle star A. filiformis. The numerous burrows were intensively irrigated enhancing the benthic in situ O 2 uptake by *50 %, and inducing highly variable redox conditions and O 2 distribution in the surface sediment as also documented by complementary laboratory-based planar optode measurements. The average benthic O 2 exchange as derived by chamber incubations and the eddy covariance approach were similar (14.9 ± 2.5 and 13.1 ± 9.0 mmol m -2 day -1 ) providing confidence in the two measuring approaches. Moreover, the non-invasive eddy approach revealed a flow-dependent benthic O 2 flux that was partly ascribed to enhanced ventilation of infauna burrows during periods of elevated flow rates. The ratio in exchange rates of RCO 2 and O 2 was close to unity, confirming that the O 2 uptake was a good proxy for the benthic carbon mineralization in this setting. The infauna activity resulted in highly dynamic redox conditions that presumably facilitated an efficient degradation of both terrestrial and marine-derived organic material. The complex O 2 dynamics of the burrow environment also concurrently stimulated nitrification and coupled denitrification rates making the sediment an efficient sink for bioavailable nitrogen. Furthermore, bioturbation mediated a high efflux of dissolved phosphorus and silicate. The study documents a high spatial and temporal variation in benthic solute exchange with important implications for benthic turnover of organic carbon and nutrients. However, more long-term in situ investigations with like approaches are required to fully understand how environmental events and spatio-temporal variations interrelate to the overall biogeochemical functioning of coastal sediments.

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Oxygen microprofiles measured in situ in deep ocean sediments

Cited by 143 publications

References 14 publications

Origin of the deep Bering Sea nitrate deficit: Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes

Origin of the deep Bering Sea nitrate deficit: Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes

Particle age distributions and O₂ exposure times: Timescales in bioturbated sediments

Benthic Carbon Mineralization and Nutrient Turnover in a Scottish Sea Loch: An Integrative In Situ Study

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Oxygen microprofiles measured in situ in deep ocean sediments

Cited by 143 publications

References 14 publications

Origin of the deep Bering Sea nitrate deficit: Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes

Origin of the deep Bering Sea nitrate deficit: Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes

Particle age distributions and O2 exposure times: Timescales in bioturbated sediments

Benthic Carbon Mineralization and Nutrient Turnover in a Scottish Sea Loch: An Integrative In Situ Study

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Particle age distributions and O₂ exposure times: Timescales in bioturbated sediments