Sediment-water exchange in shallow water estuarine sediments

Emerson, Steven; Jahnke, Richard A.; Heggie, David T.

doi:10.1357/002224084788505942

Cited by 242 publications

(127 citation statements)

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“…Particulate species are also affected by enhanced solute exchange with overlying waters. Simulations undertaken with the model in which bioirrigation was included as a nonlocal reaction term (Boudreau 1984;Emerson et al 1984) demonstrate that iron oxyhydroxides persist for longer when bioirrigators are present due to enhanced oxygenation of surficial sediment. As a result, they are able to crystallize into forms unavailable for dissimilatory iron reduction (see reaction R21) and are, thus, retained within the sediment for longer.…”

Section: Methodsmentioning

confidence: 99%

Sedimentary phosphorus dynamics and the evolution of bottom‐water hypoxia: A coupled benthic–pelagic model of a coastal system

Reed

Slomp

Gustafsson

2011

Limnology & Oceanography

143

131

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The present study examines oxygen and phosphorus dynamics at a seasonally hypoxic site in the Arkona basin of the Baltic Sea. A coupled benthic-pelagic reactive-transport model is used to describe the evolution of bottomwater solute concentrations, as well as pore-water and sediment profiles. Aerobic respiration dominates remineralization, with iron reduction, denitrification, and sulphate reduction playing secondary roles, while other pathways are negligible. Sediments represent a significant oxygen sink chiefly due to the aerobic degradation of organic matter, as well as nitrification and iron oxyhydroxide precipitation. Most phosphorus deposited in sediments is in organic matter, yet cycling is dominated by iron-bound phosphorus due to rapid dissimilatory iron reduction coupled with aerobic iron oxyhydroxide formation. Sustained hypoxia results in an initial decrease in sediment phosphorus content due to dissolution of phosphorus-bearing iron oxyhydroxides, resulting in a pulse of phosphate to overlying waters. Although an organic-rich layer is formed under low-oxygen conditions, enhanced remineralization of organic phosphorus relative to organic carbon tempers sedimentary phosphorus accumulation. Upon reoxygenation of bottom waters after a decade of sustained hypoxia, oxygen concentrations do not immediately achieve values observed prior to hypoxia because the organic-rich layer creates a higher benthic oxygen demand. Artificial reoxygenation of bottom waters leads to a substantial increase in the ironbound phosphorus pool; the total phosphorus content of the sediment, however, is unaffected. A relapse into hypoxia would consequently produce a large pulse of phosphate to the overlying waters potentially exacerbating the situation.

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Section: Methodsmentioning

confidence: 99%

Sedimentary phosphorus dynamics and the evolution of bottom‐water hypoxia: A coupled benthic–pelagic model of a coastal system

Reed

Slomp

Gustafsson

2011

Limnology & Oceanography

143

131

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“…We have modeled the process using a method that was pioneered by Christiansen et al (1984) and Emerson et al (1984) and placed in a theoretical framework by Boudreau (1984). The procedure treats solute transport by irrigation as a quasi-onedimensional process in which the transport by irrigation between overlying water and bulk sediments, at a given depth in the sediment column, is calculated as the product of a transport parameter (α, in units of time -1 ) and the difference in concentration of a solute between the pore waters at the given depth and bottom water.…”

Section: Treatment Of Sediment Irrigationmentioning

confidence: 99%

Insights on geochemical cycling of U, Re and Mo from seasonal sampling in Boston Harbor, Massachusetts, USA

Morford

Martin

Kalnejais

et al. 2007

Geochimica et Cosmochimica Acta

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3Benthic chamber experiments including the nonreactive solute tracer, Br -, indicated that sediment irrigation was very important to solute exchange at the study site.The enhancement of sediment-seawater exchange due to irrigation was determined for the nonreactive tracer (Br -), TCO 2 , NH 4 + , U and Mo. The comparisons between these solutes showed that reactions within and around the burrows were very important for modulating the Mo flux, but less important for U. The effect of these reactions on Mo exchange was highly variable, enhancing Mo (and, to a lesser extent, U) uptake at times of relatively modest irrigation, but inhibiting exchange when irrigation rates were faster.These results reinforce the observation that Mo can be released to and removed from pore waters via sedimentary reactions.The removal rate of U and Mo from seawater by sedimentary reactions was found to agree with the rate of accumulation of authigenic U and Mo in the solid phase. The fluxes of U and Mo determined by in situ benthic flux chamber measurements were the largest that have been measured to date. These results confirm that removal of redoxsensitive metals from continental margin sediments underlying oxic bottom water is important, and suggest that continental margin sediments play a key role in the marine budgets of these metals.4

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“…Although for coastal regions like the Amazon Shelf or Monterey Bay high fluxes of 0.46 mol m À 2 yr À 1 or 2.28 mol m À 2 yr À 1 were observed (Tréguer and De La Rocha, 2013), still little is known about the benthic silica cycle in temperate coastal, shallow water environments. In these areas the benthic silica cycle varies over seasonal time scales, is closely coupled to processes in surface waters and is often affected by benthic macrofauna (Aller, 1980;Emerson et al, 1984;Ragueneau et al, 2002Ragueneau et al, , 2005. After spring phytoplankton blooms benthic macrofauna can for example accumulate bSi in surface sediments due to filtration and biodeposits.…”

Section: Introductionmentioning

confidence: 99%

Seasonal dynamics of the biogenic silica cycle in surface sediments of the Helgoland Mud Area (southern North Sea)

Oehler

Schlüter

Schückel

2015

Continental Shelf Research

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a b s t r a c tIn coastal waters and the ocean silicic acid (Si(OH) 4 ) is a key nutrient for primary producers (e.g. diatoms) and other siliceous organisms, because it is required for the formation of frustules and other hard parts made of biogenic silica (bSi). Especially in shallow waters like the southern North Sea, dissolution of bSi in surface sediments and the reflux of silicic acid from sediments into the water column is an important feedback mechanism for sustaining primary production. We investigated the temporal variability of benthic silicic acid fluxes and the recycling efficiency of bSi in surface sediments of the Helgoland Mud Area (southern North Sea). For this purpose we used different methods including a benthic chamber lander system for in situ flux studies of Si(OH) 4 , ex situ sediment incubations, pore water studies and sediment analysis. . The relevance of biological mediated transport for the recycling of Si(OH) 4 was underlined by comparing in situ and ex situ sediment incubations, pore water studies, as well as depth profiles of benthic macrofauna. Mass budget calculations indicate that about 1.7-2.2 mol bSi m À 2 settle annually at the seafloor, off which about 60-81% are recycled within surface sediments and transported back into the water column.

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Sediment-water exchange in shallow water estuarine sediments

Cited by 242 publications

References 0 publications

Sedimentary phosphorus dynamics and the evolution of bottom‐water hypoxia: A coupled benthic–pelagic model of a coastal system

Sedimentary phosphorus dynamics and the evolution of bottom‐water hypoxia: A coupled benthic–pelagic model of a coastal system

Insights on geochemical cycling of U, Re and Mo from seasonal sampling in Boston Harbor, Massachusetts, USA

Seasonal dynamics of the biogenic silica cycle in surface sediments of the Helgoland Mud Area (southern North Sea)

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