Effect of eelgrass Zostera marina canopies on flow and transport

Abdelrhman, Mohamed A.

doi:10.3354/meps248067

Cited by 64 publications

(62 citation statements)

References 61 publications

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“…Because of complex interactions between waves, currents, and tides in seagrass meadows, their frictional drag cannot be characterized by single-parameter equations, even when they are homogeneous (Teeter et al 2001). The only feasible approach to this problem, and the one used herein, is to analyze smallscale processes (e.g., Abdelrhman 2003) and infer from these the macroscale implications.…”

Section: Acknowledgmentsmentioning

confidence: 99%

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Hydrodynamics of model Posidonia oceanica patches in shallow water

2005

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The hydrodynamics of simulated patches of the Mediterranean seagrass Posidonia oceanica were studied in laboratory flume experiments in which the height of the pronated canopy was always greater than half the total water depth. The effects of variations in speed (from 0.08 m s Ϫ1 to 0.24 m s Ϫ1) and patch configuration on the hydrodynamics were investigated. Significant speeds penetrated the patches to approximately half their height. Reducing speed did not change the flow patterns observed, except to weaken and blur them. Flow encountering a single patch formed a turbulent wake at the height of the top of the canopy. Within this wake, the vertical shear stress decreased monotonically downstream, but the Reynolds stress increased initially and then decayed. When a second patch was positioned within the region where Reynolds stress increased (referred to as the ''06 patch''), the wake center penetrated it, causing average turbulent velocities with horizontal components 3.3 times higher and vertical components 4.2 times higher than in the upstream patch. When this patch was positioned where the Reynolds stress decayed (referred to as the ''14 patch''), the wake center rose above it. Nevertheless, the turbulence in the 14 patch had horizontal components 12% higher and vertical components 22% higher on average than in the 06 patch because its upstream end was closer to the Reynolds stress maximum. Thus the ratio of the patch separation to the length of wake in which the Reynolds stress increased was identified as central to quantifying the turbulence within the downstream patch. The increased turbulence is likely to be important in determining sedimentary and ecological patch characteristics by increasing retention of particulates in suspension and thus reducing depositional rates of, for example, larvae, nutrients, and dead organic matter.

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Section: Acknowledgmentsmentioning

confidence: 99%

“…Abdelrhman (2003) has provided a mathematical model of many of these effects. Patchiness of seagrass meadows alters the nature of this interaction.…”

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confidence: 99%

Hydrodynamics of model Posidonia oceanica patches in shallow water

2005

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“…For simplicity and as a first order approximation, I assumed that this difference would be distributed uniformly throughout the overlying water column. Abdelrhman (2003) presented a rigorous theoretical solution that can apply to the flow above the canopy.…”

Section: And (16)mentioning

confidence: 99%

“…By trapping sediments, SAV keeps the water clear, which in turn increases the transmission of light and allows the plants to grow. Similarly, eelgrass affects transport conditions in its vicinity (Abdelrhman 2003) by altering the exchange of water, which affects sedimentation, recycling of nutrients and recruitment of fauna (Kenworthy et al 1980, Eckman 1987, Rybicki et al 1997. Seagrass meadows may be regarded as net sinks of detritus in areas with low currents and as sources in areas with high currents (Fonseca et al 1983, Koch 1999.…”

Section: Introductionmentioning

confidence: 99%

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Modeling coupling between eelgrass Zostera marina and water flow

Abdelrhman¹

2007

Mar. Ecol. Prog. Ser.

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Ecological effects caused by submerged aquatic vegetation not only depend on the plants and their morphology but also on the flow and transport patterns of dissolved and suspended constituents near the canopy. Canopy height is a major variable in any quantitative analysis of plant biomass and constituent transport in its vicinity. Height of eelgrass Zostera marina canopies changes due to bending of the blades under varying current regimes. In this paper, I mathematically modeled the coupling between eelgrass blade bending and water flow. Based on the balance of forces of drag, lift, friction, weight and buoyancy on a single blade, the model defined the bending of blades (i.e. height of canopy) and the flow response within and above the canopy. This coupling was tested using laboratory data and indicated that the model performed adequately. Both model results and laboratory data confirmed that the bending of blades, and hence canopy height, was very sensitive to current magnitude and directly influenced current profile. Identifying canopy height is a major factor in defining spatial distribution of grass biomass from optical or acoustic remote sensing devices. The model has direct implications for biological issues related to the plants themselves and to their associated organisms, such as the vertical distribution of photosynthesis within the canopy and the effect of current shear on recruitment of organisms on the blades. It can also be used to study how eelgrass canopies affect horizontal transport of constituents, such as dissolved oxygen, nutrients and organic carbon, and particulate material such as pollen, larvae, plankton and detritus.

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Sediment transport and shear stress partitioning in a vegetated flow

Bouteiller

Venditti

2015

Water Resources Research

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Vegetation is a common feature in natural coastal and riverine water ways, interacting with both the water flow and sediment transport. However, the physical processes governing these interactions are still poorly understood, which makes it difficult to predict sediment transport and morphodynamics in a vegetated environment. We performed a simple experiment to study how sediment transport responds to the presence of flexible, single-blade vegetation, and how this response is influenced by the vegetation density. We found that the skin friction and sediment transport are reduced in a plant patch, and that this effect is larger for denser vegetation. We then evaluated several methods to calculate the skin friction in a vegetated flow, which is the key to sediment transport prediction. Among these, the inversion of bed load transport formulas and the Einstein and Banks (1950) methods appeared to produce the most reasonable values of the skin friction. Finally, we suggest using the parameter a, which is the ratio of the skin friction computed by these methods to the total bed shear stress, to make more realistic sediment transport predictions in morphodynamic models.

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Effect of eelgrass Zostera marina canopies on flow and transport

Cited by 64 publications

References 61 publications

Hydrodynamics of model Posidonia oceanica patches in shallow water

Hydrodynamics of model Posidonia oceanica patches in shallow water

Modeling coupling between eelgrass Zostera marina and water flow

Sediment transport and shear stress partitioning in a vegetated flow

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