Quantifying Seasonal Seagrass Effects on Flow and Sediment Dynamics in a Back‐Barrier Bay

Zhu, Qiao; Wiberg, Patricia L.; Reidenbach, Matthew A.

doi:10.1029/2020jc016547

Cited by 24 publications

(40 citation statements)

References 71 publications

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“…Both plant communities trap sediment, which is critical for their resilience to environmental change. However, how sediment might be exchanged between the two communities has rarely been investigated (Donatelli et al, 2018;Zhu et al, 2021). A sediment budget is a useful tool for examining this exchange, as it accounts for both the losses and gains of sediment and can help assess whether a planned restoration of a tidal marsh has a high probability of success (Ganju et al, 2013(Ganju et al, , 2019.…”

Section: Introductionmentioning

confidence: 99%

Sediment Exchange Between the Created Saltmarshes of Living Shorelines and Adjacent Submersed Aquatic Vegetation in the Chesapeake Bay

2021

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Rising sea levels and the increased frequency of extreme events put coastal communities at serious risk. In response, shoreline armoring for stabilization has been widespread. However, this solution does not take the ecological aspects of the coasts into account. The “living shoreline” technique includes coastal ecology by incorporating natural habitat features, such as saltmarshes, into shoreline stabilization. However, the impacts of living shorelines on adjacent benthic communities, such as submersed aquatic vegetation (SAV), are not yet clear. In particular, while both marshes and SAV trap the sediment necessary for their resilience to environmental change, the synergies between the communities are not well-understood. To help quantify the ecological and protective (shoreline stabilization) aspects of living shorelines, we presented modeling results using the Delft3D-SWAN system on sediment transport between the created saltmarshes of the living shorelines and adjacent SAV in a subestuary of Chesapeake Bay. We used a double numerical approach to primarily validate deposition measurements made in the field and to further quantify the sediment balance between the two vegetation communities using an idealized model. This model used the same numerical domain with different wave heights, periods, and basin slopes and includes the presence of rip-rap, which is often used together with marsh plantings in living shorelines, to look at the influences of artificial structures on the sediment exchange between the plant communities. The results of this study indicated lower shear stress, lower erosion rates, and higher deposition rates within the SAV bed compared with the scenario with the marsh only, which helped stabilize bottom sediments by making the sediment balance positive in case of moderate wave climate (deposition within the two vegetations higher than the sediment loss). The presence of rip-rap resulted in a positive sediment balance, especially in the case of extreme events, where sediment balance was magnified. Overall, this study concluded that SAV helps stabilize bed level and shoreline, and rip-rap works better with extreme conditions, demonstrating how the right combination of natural and built solutions can work well in terms of ecology and coastal protection.

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Section: Introductionmentioning

confidence: 99%

Sediment Exchange Between the Created Saltmarshes of Living Shorelines and Adjacent Submersed Aquatic Vegetation in the Chesapeake Bay

2021

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“…Many estuarine seagrass ecosystems face increasing hydrological alterations caused by human activities and climate change, which further alters sediment dynamics including sedimentation, resuspension, etc., and induces water turbidity and bed level changes (Palinkas and Koch, 2012;João et al, 2013). Feedback between seagrass meadows and sediment dynamics has been recognized as being vital to seagrass restoration (Suykerbuyk et al, 2016;Zhu et al, 2021), further studies are thus needed to investigate the influence of sediment dynamics on the distribution pattern and ecogeomorphological processes of seagrass meadows.…”

Section: Discussionmentioning

confidence: 99%

How Turbidity Mediates the Combined Effects of Nutrient Enrichment and Herbivory on Seagrass Ecosystems

et al. 2022

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While nutrient enrichment and herbivory have been well recognized as the main driving factors of seagrass meadow fragmentation and degradation, there is limited understanding of how their relative importance shifts across large spatial scales where environmental factors such as turbidity can vary. In this study, a field control experiment was conducted in two Zostera japonica meadows distributed on the two banks of the Yellow River Estuary with different turbidity, to investigate the combined effects of nutrient enrichment and herbivory on seagrass and macroalgae. Our results showed that turbidity had the mediating force of shifting the relative importance of nutrient enrichment and herbivory to seagrass and macroalgae. While herbivory played a vital role in maintaining the balance between the two primary producers in a turbid environment, nutrient enrichment tended to offset herbivory-induced biomass loss by promoting seagrass growth in a less turbid system. Additionally, two potential mechanisms that might regulate the responses of seagrasses and macroalgae to nutrient enrichment and herbivory under different turbidity are proposed. On the one hand, turbidity might mediate the feeding preference of herbivores. On the other hand, nutrient enrichment favors the growth of opportunistic macroalgae over seagrass in turbid systems. Our study emphasizes the mediating force of turbidity on seagrass ecosystems, and provides references for the protection and restoration of seagrass meadows under multiple environmental stressors, and prompts further studies on the feedback between sediment dynamics and seagrass meadows in the context of ecogeomorphology.

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“…Net deposition increases with distance over further distances, associated with a decrease in vertical velocity and turbulent kinetic energy [121]. Due to flow obstruction by the seagrass meadows, tidal flows may be deflected around the meadow and concentrated at the edge [122]. Although flow velocity may increase by 30% at the meadow edges, it is not able to offset the loss of water flux within the meadow and the total water flux discharged through the cross-meadow may be reduced by 10% [122].…”

Section: Sediment Transport In the Edges Of Patchesmentioning

confidence: 99%

“…Due to flow obstruction by the seagrass meadows, tidal flows may be deflected around the meadow and concentrated at the edge [122]. Although flow velocity may increase by 30% at the meadow edges, it is not able to offset the loss of water flux within the meadow and the total water flux discharged through the cross-meadow may be reduced by 10% [122]. Posidonia oceanica meadows significantly buffer sediment resuspension, which may be reduced more than three-fold compared to the unvegetated sandy bottom [115].…”

Section: Sediment Transport In the Edges Of Patchesmentioning

confidence: 99%

“…A patch that is too small is not able to reduce waves and instead exhibits enhanced turbulence and scouring at meadow edges [123]. During the summer when seagrass density is high, pronounced sediment accumulation (>6 mm/month) may occur at the edges of the seagrass bed and decrease logarithmically with distance into the meadow [122]. Saltmarsh Ruppia maritima patches are characterized by a reduction in the turbulent kinetic energy and resuspended sediment concentrations decrease as the vegetation densities increase [124].…”

Section: Sediment Transport In the Edges Of Patchesmentioning

confidence: 99%

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The World of Edges in Submerged Vegetated Marine Canopies: From Patch to Canopy Scale

Colomer

Serra

2021

Water

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This review describes the world of edges in submerged vegetated marine canopies (seagrasses, saltmarshes, and seaweeds) where an edge is a boundary with a frontal area separating the vegetation from the adjacent non-vegetated zones. Plants within the vegetation are made of flexible elements pronating in the direction of the flow and oscillating back and forth in response to wave forcing. Some of them also occupy the full height within the water body. The analysis focuses on both the canopy- and local-patch scales to acquire knowledge about the hydrodynamics and the biophysical interactions in the structural shallows and deep limits of the canopies as well as on the structural edges of vegetation patches and the edges in the gaps within the canopies. The spatial arrangements of both canopy and patch edges are not only well imposed through the modification of hydrodynamics, but so too through small-scale interactions from internal structural causes and modifications. The continuous fragmentation of coastal marine habitats has reduced their structural complexity, thus making habitat edges a prevalent seascape feature, including in the shallow (or upper) and deep (or lower) limits of the canopies, the patch edges, and the edges in the gaps within the canopies. Canopy patches represent a region of high flow resistance where flow deflects and accelerates above and/or next to the canopy, resulting in an increase in water velocity and turbulence, especially at the edges of the patch. At the edges, energy transfer is found in spectral wave velocities from the longer to shorter wave period components. Likewise, at the edges, the net deposition of sediments decreases over a distance to a certain length, relative to the bare bed, which is associated with a region of vertical updraft and elevated turbulent kinetic energy. The edge effects also relate to the influence that a patch edge can have on determining species composition and predation risk, which is additionally mediated by the effect the edges have on habitat complexity within the vegetated patch. Organism feedback within the edges does not simply follow the canopy and local features and, in fact, the intricate interaction between biogeophysical processes is key in explaining the complexity of coastal submerged canopy landscapes. For example, proximity to patch edges has a greater influence on epifaunal density and community structure than structural complexity or predation do. The extent to which edges reduce predation risk depends on the extent to which they support higher structural complexities compared to patch interiors. The canopies’ shallow limits and their position in the underwater beach profile are mostly limited by light availability, the intensity of the wave action, and the local nearshore hydrodynamics, but they also depend on the local structural conditions at the vegetated side. The deep limits of the canopies, however, mainly depend on the availability of light and research findings support migration both to the deeper and shallower layers. All structural edges face changes caused by increasing nutrient inputs, development of coastal zones and the increasing impact of climate change. A considerable challenge to managing, restoring, and conserving coastal marine ecosystems stems from understanding how the canopies are able to cope with these natural and anthropogenic disturbances.

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Quantifying Seasonal Seagrass Effects on Flow and Sediment Dynamics in a Back‐Barrier Bay

Cited by 24 publications

References 71 publications

Sediment Exchange Between the Created Saltmarshes of Living Shorelines and Adjacent Submersed Aquatic Vegetation in the Chesapeake Bay

Sediment Exchange Between the Created Saltmarshes of Living Shorelines and Adjacent Submersed Aquatic Vegetation in the Chesapeake Bay

How Turbidity Mediates the Combined Effects of Nutrient Enrichment and Herbivory on Seagrass Ecosystems

The World of Edges in Submerged Vegetated Marine Canopies: From Patch to Canopy Scale

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