Control of the diffusive boundary layer on benthic fluxes: a model study

Kelly-Gerreyn, B.A.; Hydes, D.J.; Waniek, Joanna J

doi:10.3354/meps292061

Cited by 17 publications

(13 citation statements)

References 40 publications

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“…In a recent nondynamic model study by Kelly-Gerreyn et al (2005), the maximum increase in the benthic O 2 uptake following the elimination of a 1-mm-thick DBL was estimated to be 22%. This, however, was for sediments that were dominated by aerobic mineralization, with high lability of the entire organic carbon pool, relatively shallow O 2 penetration depth (2-4 mm), no metal cycling, and sulfate reduction fueled mainly by sulfate from the benthic sulfide oxidation.…”

Section: Discussionmentioning

confidence: 97%

Effect of the diffusive boundary layer on benthic mineralization and O₂ distribution: A theoretical model analysis

Glud

Berg

Fossing³

et al. 2007

Limnology & Oceanography

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On the basis of a dynamic diagenetic model, we evaluate and discuss the effect of the diffusive boundary layer (DBL) on benthic O 2 exchange and O 2 consuming pathways. The analysis documents that the DBL has only minor importance for the annual O 2 uptake of coastal cohesive sediments. Imposing static DBL thicknesses of 300-900 mm decreased the annual O 2 uptake by only 2-10% in comparison to a situation without any DBL. Lower O 2 availability as imposed by a thicker DBL, however, markedly reduced the aerobic heterotrophic respiration but enhanced aerobic reoxidation of solutes released by the stimulated anaerobic respiration. The 2-10% decrease in the annual O 2 uptake was caused mainly by higher benthic release rates of NH þ 4 and Mn 2+ . The overall carbon degradation rate-and thus the carbon preservation-remained unaffected by the DBL thickness. Dynamic modeling revealed that abrupt changes in the DBL thickness caused an instantaneous change in the interstitial O 2 distribution and in the benthic O 2 uptake rate. However, conditions quickly reversed as the porewater profiles of reduced solutes and distribution of reduced solids readjusted even though full steady state was obtained only after several months. In nature the DBL is constantly changing, and thus in situ O 2 microprofiles are transient by nature. Dynamic modeling showed that the benthic O 2 concentration and the O 2 uptake in Aarhus Bay could vary by 30% or more on time scales of a few hours or days solely because of changes in the DBL thickness. The integrated annual O 2 uptake remained unaffected by these fluctuations.

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Section: Discussionmentioning

confidence: 97%

Effect of the diffusive boundary layer on benthic mineralization and O₂ distribution: A theoretical model analysis

Glud

Berg

Fossing³

et al. 2007

Limnology & Oceanography

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“…Indeed, the DBL thickness is linked to the level of turbulence in the water column and influences O 2 fluxes at the sediment water interface by changing the diffusion path length to the thin oxic sediment layer (Berner, 1980;Lorke et al, 2003;Kelly-Gerreyn et al, 2005;Roy et al, 2002;Brand et al, 2009). A thicker DBL due to difficulties in mimicking in situ turbulences can cause a decreased oxygen availability and result in an overall decrease of sediment oxygen uptake (Glud et al, 2007).…”

Section: Comparison Of In Situ and Ex Situ Diffusive Oxygen Uptake Ratesmentioning

confidence: 99%

Temporal variability of carbon recycling in coastal sediments influenced by rivers: assessing the impact of flood inputs in the Rhône River prodelta

et al. 2010

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Abstract. River deltas are particularly important in the marine carbon cycle as they represent the transition between terrestrial and marine carbon: linked to major burial zones, they are reprocessing zones where large carbon fluxes can be mineralized. In order to estimate this mineralization, sediment oxygen uptake rates were measured in continental shelf sediments and river prodelta over different seasons near the outlet of the Rhône River in the Mediterranean Sea. On a selected set of 10 stations in the river prodelta and nearby continental shelf, in situ diffusive oxygen uptake (DOU) and laboratory total oxygen uptake (TOU) measurements were performed in early spring and summer 2007 and late spring and winter 2008. In and ex situ DOU did not show any significant differences except for shallowest organic rich stations. Sediment DOU rates show highest values concentrated close to the river mouth (approx. 20 mmol O 2 m −2 d −1 ) and decrease offshore to values around 4.5 mmol O 2 m −2 d −1 with lowest gradients in a south west direction linked to the preferential transport of the finest riverine material. Core incubation TOU showed the same spatial pattern with an averaged TOU/DOU ratio of 1.2±0.4. Temporal variations of sediment DOU over different sampling periods, spring summer and late fall, were limited and benthic mineralization rates presented a stable spatial pattern.Correspondence to: C. Cathalot (cecile.cathalot@lsce.ipsl.fr) A flood of the Rhône River occurred in June 2008 and delivered up to 30 cm of new soft muddy deposit. Immediately after this flood, sediment DOU rates close to the river mouth dropped from around 15-20 mmol O 2 m −2 d −1 to values close to 10 mmol O 2 m −2 d −1 , in response to the deposition near the river outlet of low reactivity organic matter associated to fine material. Six months later, the oxygen distribution had relaxed back to its initial stage: the initial spatial distribution was found again underlining the active microbial degradation rates involved and the role of further deposits. These results highlight the immediate response of the sediment oxygen system to flood deposit and the rapid relaxation of this system towards its initial state (6 months or less) potentially linked to further deposits of reactive material.

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“…It is well known that local hydrodynamics influence nutrient fluxes through porewater advection (Huettel & Webster 2001), desorption from suspended sediments (Morin & Morse 1999), and thinning of the diffusive boundary layer (Kelly-Gerreyn et al 2005). Benthic macrophytes can have significant effects on these fluxes physically, by deflecting flow and changing the hydrodynamic conditions at the sediment surface, and biologically, by uptake and indirect effects on bacterial nutrient transformations in the sediment ).…”

Section: Introductionmentioning

confidence: 99%

Enhancement of sediment suspension and nutrient flux by benthic macrophytes at low biomass

Lawson¹,

McGlathery²,

Wiberg³

2012

Mar. Ecol. Prog. Ser.

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In shallow coastal ecosystems where most of the seafloor typically lies within the photic zone, benthic autotrophs dominate primary production and mediate nutrient cycling and sediment stability. Because of their different structure and metabolic rates, the 2 functional groups of benthic macrophytes (seagrasses, macroalgae) have distinct influences on benthic−pelagic coupling. Most research to date in these soft-bottomed systems has focused on mature seagrass meadows where shoot densities are high and on dense macroalgal mats that accumulate in response to eutrophication. Relatively little is known about the influence of low-biomass stands of seagrass and macroalgae on nutrient fluxes and sediment suspension. Using an erosion microcosm with controlled forcing conditions, we tested the effects of the eelgrass Zostera marina L. and the invasive macroalga Gracilaria vermiculophylla on sediment suspension and nutrient fluxes under high-flow conditions. At low densities, G. vermiculophylla increased sediment suspension and increased the nutrient flux from the sediment to the water column. For macroalgae, increased sedi ment suspension is likely due to dislodgement of sediment particles by bedload transport of the algae. In this case, the increase in sediment transport was reflected in an increase in nutrient flux from the sediment, showing that modification of physical forcing by benthic primary producers can also affect nutrient flux. The presence or absence of Z. marina did not have a significant effect on nutrient flux. However, the results suggest that there may be a range of low shoot densities for which storm-like flows increase sediment suspension to values higher than those expected for a bare sediment bed.

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Control of the diffusive boundary layer on benthic fluxes: a model study

Cited by 17 publications

References 40 publications

Effect of the diffusive boundary layer on benthic mineralization and O₂ distribution: A theoretical model analysis

Effect of the diffusive boundary layer on benthic mineralization and O₂ distribution: A theoretical model analysis

Temporal variability of carbon recycling in coastal sediments influenced by rivers: assessing the impact of flood inputs in the Rhône River prodelta

Enhancement of sediment suspension and nutrient flux by benthic macrophytes at low biomass

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Control of the diffusive boundary layer on benthic fluxes: a model study

Cited by 17 publications

References 40 publications

Effect of the diffusive boundary layer on benthic mineralization and O2 distribution: A theoretical model analysis

Effect of the diffusive boundary layer on benthic mineralization and O2 distribution: A theoretical model analysis

Temporal variability of carbon recycling in coastal sediments influenced by rivers: assessing the impact of flood inputs in the Rhône River prodelta

Enhancement of sediment suspension and nutrient flux by benthic macrophytes at low biomass

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Effect of the diffusive boundary layer on benthic mineralization and O₂ distribution: A theoretical model analysis

Effect of the diffusive boundary layer on benthic mineralization and O₂ distribution: A theoretical model analysis