In situ benthic oxygen fluxes in a near-shore coastal marine system: a new approach to quantify the effect of wave action

Malan, DE; McLachlan, Anton

doi:10.3354/meps073069

Cited by 29 publications

(19 citation statements)

References 43 publications

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“…data), indicating only 23% of the flux measured in the dark by the eddycorrelation method at its maximum (Case 6, Table 3). This underestimate could be due to the exclusion of porewater pressure fluctuations by waves and ripple topography in the enclosed system (Precht & Huettel 2003), even though wave-induced advective porewater transport supports a high oxygen-uptake rate associated with mineralization of dissolved and particulate organic matter in sandy sediments (Malan & McLachlan 1991, de Beer et al 2005.…”

Section: Importance Of Wavesmentioning

confidence: 99%

Oxygen exchange flux between sediment and waterin an intertidal sandflat, measured in situ by the eddy-correlation method

Kuwae¹,

Kamio²,

Inoue³

et al. 2006

Mar. Ecol. Prog. Ser.

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High temporal-resolution fluctuations in oxygen concentration and vertical velocity were measured over an intertidal sandflat (water depth < 69 cm) using an oxygen microelectrode and an acoustic Doppler velocimeter, in order to estimate oxygen flux across the sediment -water interface using the eddy-correlation method. The effect of flux estimate procedures, including noise removal and extraction of fluctuating components, was investigated. The estimated oxygen effluxes from the sediment ranged from -3.2 to 6.6 mmol O 2 m -2 h -1 in the light and from -14.5 to -6.6 mmol O 2 m -2 h -1 in the dark. The oxygen-uptake fluxes in the dark were markedly higher than those measured by a conventional enclosure technique. High-frequency turbulence and/or noise (> 5 Hz) observed in the vertical velocity and oxygen concentration data made little contribution to the total oxygen flux (0 to 7%). However, trends (steady change over a longer time scale) caused significant artifacts in the estimated fluxes for several cases. Thus, removal of trends from raw time-series data is recommended. The co-spectrum of the fluctuating components of vertical velocity and oxygen concentration revealed that the oxygen flux at a frequency band between 0.3 and 1.4 Hz (at a period from 0.7 to 3.3 s) was a major contributor to the total oxygen flux. This frequency was consistent with the dominant frequency of vertical velocity, indicating that transport and exchange of porewater and overlying water by wind-induced waves may be crucial processes to dissolved oxygen flux between permeable sandy sediments and shallow waters.

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Section: Importance Of Wavesmentioning

confidence: 99%

Oxygen exchange flux between sediment and waterin an intertidal sandflat, measured in situ by the eddy-correlation method

Kuwae¹,

Kamio²,

Inoue³

et al. 2006

Mar. Ecol. Prog. Ser.

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“…In areas exposed to tidal waves and strong bottom currents, hydrodynamic forces can resuspend and thereby oxygenate surficial sediment or flush the interstices with oxygen-rich water (Riedl et al 1972, Malan & McLachlan 1991.…”

Section: Introductionmentioning

confidence: 99%

Impact of biogenic sediment topography on oxygen fluxes in permeable seabeds

Ziebis

Huettel

Förster

1996

Mar. Ecol. Prog. Ser.

137

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ABSTRACT. Boundary layer flows, interacting with roughness elements at the sediment surface, alter the small-scale flow reglme. Consequently, pressure d~fferences are generated that are the drivlng forces for advective pore-water flow. We ~nvestigated topography-induced transport of oxygen in a permeable coastal sediment from the Mediterranean Sea (Isola del Giglio, Italy). The sediment surface was characterized by a high abundance (120 m-2) of sediment mounds (average height: 4 cm) built by the mud shrimp Callianassa truncata (Decapoda, Thalassinidea). Boundary layer flow velocities recorded in situ ranged between 2 and 16 cm S-' Detailed experiments were performed in a recirculating laboratory flow channel A natural sediment core, 20 cm deep with a surface area of 0 3 m" was exposed to a unidirectional flow of varying current velocity (3, 6, 10 cm S S ' ) . The alteration of the small-scale flow reglme a t a sediment mound was documented by vertical velocity profiles measured in 1 mm resolution with temperature-compensated thermistor probes. Oxygen distribution in the sediment was investigated with Clark-type microelectrodes. At a smooth surface, oxygen penetration depth in the permeable sediment did not exceed 4 mm, independent of flow velocity. In contrast, the topography-induced advective oxygen transport increased significantly with current speed. Oxygen reached down to almost 40 mm at the upstream foot of a 1 cm high sediment mound at a flow velocity of 10 cm S-' Thus, the oxic sediment volume increased locally by a factor of 4.8 compared to the oxic zone underneath a smooth surface. At a natural abundance of 120 mounds m-? the oxic sediment volume per mZ seabed was calculated to be 3.3-fold higher than in a seabed with a smooth surface. In a parallel experiment, advective solute transport was also demonstrated in a less permeable sediment (k = 5 r 10-12 m') from the North Sea intertidal flat. Due to the lower permeability the effect on O2 transport was less than in the Mediterranean sand, but oxygen penetration depth increased locally 2-fold a t a sediment mound under a flow velocity of 10 cm S-' The experiments showed the high spatial and temporal variability of oxygen distnbution in a coastal seabed depending on sediment surface topography, boundary layer flow velocities and sediment permeability.

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“…On the basis of field observations, those authors presented model calculations that suggested that the subtidal pump could filter the complete ocean volume in only 14,000 yr. Rutgers van der Loeff (1981) described the same process as increased diffusivity in the upper 1-1.5 cm of intertidal sandy sediment under low to moderate wave action. To include the wave pumping in their in situ flux measurements, Malan and McLachlan (1991) deployed benthic chambers with flexible membrane tops that revealed that oxygen consumption and solute fluxes are positively correlated with wave action. However, it is not obvious how the circular motion of pore water within sediment can cause net solute transport, because the displacement through the wave cycle guides the fluid back to its origin.…”

mentioning

confidence: 99%

Advective pore‐water exchange driven by surface gravity waves and its ecological implications

Precht

Huettel

2003

Limnology & Oceanography

190

159

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The effects of surface gravity waves on pore-water release from permeable sediment (k ϭ 1.3-1.8 ϫ 10 Ϫ11 m 2 ) in shallow water were studied in a wave tank. Our tracer experiments demonstrated that shallow-water waves can increase fluid exchange between sandy sediment and overlying water 50-fold, relative to the exchange by molecular diffusion. The main driving force for this increased exchange are the pressure gradients generated by the interaction of oscillating boundary flows and sediment wave ripples. These gradients produce a pore-water flow field, with a regular pattern of intrusion and release zones, that migrates with ripple propagation. The ensuing topography-related filtering rates in the wave tank ranged from 60 to 590 L m Ϫ2 d Ϫ1 and exceeded the solute exchange rates caused by hydrostatic wave pumping (38 L m Ϫ2 d Ϫ1 ) and initial molecular diffusion (corresponding to 10-12 L m Ϫ2 d Ϫ1 ). Wave-induced filtration is ecologically relevant because permeable sandy sediments are very abundant on the continental margins and can be converted into effective filter systems, which suggests that these sediments are sites for rapid mineralization and recycling. We propose that the wave influenced continental shelf may be subdivided into two zones: a shallow zone (water depth Ͻ wavelength/2), where wave orbital motion at the sea floor creates ripples and causes topography related advective filtering; and a deeper zone (wavelength/2 Ͻ water depth Ͻ wavelength), where wave pumping enhances interfacial exchange by hydrostatic pressure oscillations.Physical and biological transport link the biogeochemical processes in the water column and sediment. Whereas molecular diffusion and, locally, also bioturbation are the major transport mechanisms in the cohesive, fine-grained deep-sea deposits (Berner 1980;Aller 1982Aller , 2001), solute transport caused by pore-water flows increases in importance in permeable sandy shelf sediments. Here, boundary layer flows, interacting with sea-bed topography, induce pressure differences at the sediment-water interface that lead to pore-water motion in permeable sediments. The ensuing advective transport can exceed transport by molecular diffusion by several orders of magnitude (Huettel and Webster 2001).In areas where water depth (D) is smaller than half the wavelength () of the surface gravity waves, oscillating flows are generated at the sediment-water interface by the wave orbital-water motion (e.g., Denny 1988). Webb andTheodor (1968, 1972) showed, by injecting dyed water into coarse sandy nearshore sediment and observing its reappearance at the sediment surface, that such oscillating boundary flows could drive sediment-water-interfacial fluxes. The trajectories of pore-water particles under a rippled bed over one wave period were calculated by Shum (1992). His results suggested that the zone of advection extends several ripple heights below the sediment surface over a wide range of wave conditions and sediment characteristics. Indications that surface gravity waves may b...

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In situ benthic oxygen fluxes in a near-shore coastal marine system: a new approach to quantify the effect of wave action

Cited by 29 publications

References 43 publications

Oxygen exchange flux between sediment and waterin an intertidal sandflat, measured in situ by the eddy-correlation method

Oxygen exchange flux between sediment and waterin an intertidal sandflat, measured in situ by the eddy-correlation method

Impact of biogenic sediment topography on oxygen fluxes in permeable seabeds

Advective pore‐water exchange driven by surface gravity waves and its ecological implications

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