Physical and Biological Controls on Sediment and Nutrient Fluxes in a Temperate Lagoon

Lawson, Sarah

doi:10.18130/v3bc3b

Cited by 5 publications

(11 citation statements)

References 46 publications

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“…The movement of algae caused by the increased shear stress likely enhances this effect. In a related study, we investigated the mechanisms accounting for the increased nutrient efflux from sediments in our microcosm experiments and showed that hydrodynamically-forced fluxes (advection, suspension/ desorption) were similar in magnitude to diffusive fluxes, indicating that low-flow incubations may underestimate nutrient fluxes by 50% if higher flows are present (Lawson 2008).…”

Section: Factors Affecting Nutrient Fluxesmentioning

confidence: 89%

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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Section: Factors Affecting Nutrient Fluxesmentioning

confidence: 89%

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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“…The sediments of both sites were composed of fine sands, with , 10 wt% mud (Lawson et al 2007). Sediment permeability at a nearby site was determined to be 2.5 3 10 211 m 2 in a separate study (Lawson 2008). Sediment organic content of the seagrass meadows sampled was 0.8 6 0.02 (SE) and 1.0 6 0.06 (SE) wt% for the bare sediments and showed no legacy of the prior seagrass-vegetated period.…”

Section: Methodsmentioning

confidence: 95%

“…Sediment organic content of the seagrass meadows sampled was 0.8 6 0.02 (SE) and 1.0 6 0.06 (SE) wt% for the bare sediments and showed no legacy of the prior seagrass-vegetated period. We believe this is because of the high rates of sediment redistribution in these shallow coastal bays (Lawson et al 2007). …”

Section: Methodsmentioning

confidence: 97%

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Dissolved oxygen fluxes and ecosystem metabolism in an eelgrass (Zostera marina) meadow measured with the eddy correlation technique

Hume

Berg

McGlathery

2010

Limnology & Oceanography

154

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Dissolved oxygen (DO) fluxes were measured by eddy correlation to estimate net ecosystem metabolism (NEM) during summer in a restored eelgrass (Zostera marina) meadow and a nearby, unvegetated sediment. This technique measures benthic fluxes under true in situ light and hydrodynamic conditions, integrates over a large area (typically . 100 m 2 ), and captures short-term variations. DO fluxes measured through eight 24-h periods showed pronounced temporal variation driven by light and local hydrodynamics on multiple scales: hour-to-hour, within each daily cycle, and between deployments. The magnitude of variation between hours during single deployments equaled that between deployments, indicating that short-term variation must be included for metabolism estimates to be accurate. DO flux variability was significantly correlated to mean current velocity for the seagrass site and to significant wave height for the unvegetated site. Fluxes measured in low-flow conditions analogous to many chamber and core incubations underestimated those measured in higher-flow conditions typical of in situ conditions by a factor of 2-6. Rates of gross primary production (GPP), respiration (R), and NEM varied substantially between individual deployments, reflecting variations in light and hydrodynamic conditions, and daily values of GPP and R for individual deployments were tightly linked. Average daily NEM of the seagrass site was higher than that of the unvegetated site; the seagrass site was in metabolic balance, and the unvegetated site showed a tendency toward net heterotrophy during this midsummer period.

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“…The time average is needed to take into account the difference in the bottom shear stress induced by tidal oscillations in water depth. For simplicity, we set t cr to 0.35 Pa based on measurements and modeling of sediment erosion and resuspension in the study area [Lawson, 2008].…”

Section: Wave Energy and Bottom Shear Stressesmentioning

confidence: 99%

Influence of storm surges and sea level on shallow tidal basin erosive processes

et al. 2010

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[1] The finite-element model WWTM is applied to a system of lagoons at the Virginia Coast Reserve, USA. The model solves the shallow water equations to compute tidal fluxes, and is equipped with a wave propagation module to calculate wave height during local wind events. The model is validated using measured water elevations, wave heights, and periods at five locations within the lagoon system. Scenarios with different wind conditions, storm surges, and relative sea level are simulated. Results are analyzed in terms of bottom shear stresses on the tidal flats, a measure of sediment resuspension potential, and total wave energy impacting the marsh boundaries, which is the chief process driving lateral marsh erosion. Results indicate that wave energy at the marsh boundaries is more sensitive to wind direction than are bottom shear stresses. Wave energy on marsh boundaries and bottom shear stresses on the tidal flats increase with sea level elevation, with the former increasing almost ten times more than the latter. Both positive and negative feedbacks between wave energy at the boundaries and bottom shear stresses are predicted, depending on the fate of the sediments eroded from the salt marsh boundaries.

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Physical and Biological Controls on Sediment and Nutrient Fluxes in a Temperate Lagoon

Cited by 5 publications

References 46 publications

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

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

Dissolved oxygen fluxes and ecosystem metabolism in an eelgrass (Zostera marina) meadow measured with the eddy correlation technique

Influence of storm surges and sea level on shallow tidal basin erosive processes

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