Modified hydrodynamics in canopies with longitudinal gaps exposed to oscillatory flows

Allaoui, Nazha El; Serra, Teresa; Soler, María Teresa; Colomer, Jordi; Pujol, Dolors; Oldham, Carolyn

doi:10.1016/j.jhydrol.2015.10.041

Cited by 17 publications

(17 citation statements)

References 29 publications

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“…less resilient) and allow greater penetration of waves and currents into the canopy, which will enhance sediment resuspension and favor exchange between the meadow and the gap. These conclusions support those of , while Hendriks et al (2008), El Allaoui et al (2015 and El Allaoui et al (2016) reported the buffering of sediment resuspension by P. oceanica meadows. El Allaoui et al (2016) found that canopies with large gaps had a higher mixing level than canopies with small gaps, despite both canopies having the same total gap area.…”

Section: Discussionsupporting

confidence: 84%

Impact of anthropogenically created canopy gaps on wave attenuation in a Posidonia oceanica seagrass meadow

Colomer¹,

Soler²,

Serra³

et al. 2017

Mar. Ecol. Prog. Ser.

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Fixed weights moorings, once removed, can create longitudinal gaps in seagrass meadows of different sizes, running perpendicular to the coast. We quantified the interactions between these longitudinal gaps and the hydrodynamic environment of the nearshore environment to determine their potential impact on seagrass meadow ecology. Within the meadow at leaf length distances from the edge, wave attenuation by the lateral vegetation next to the gap was approximately the same as attenuation by fully vegetated areas, and the wave attenuating capacity of the lateral, near-gap vegetation was independent of gap width. Gaps with widths less than twice the leaf length exhibited 8% wave attenuation and 11% turbulent kinetic energy attenuation, confirming that vegetation shelters at least small gaps. Despite similar capacity for wave attenuation, the longitudinal gaps influenced the architectural characteristics of the adjacent (lateral) meadow; lateral shoot density, percent cover and leaf length adjacent to the largest gap were 12, 16, and 20% lower than the fully vegetated site, respectively. Significant differences in the temporal variation of the mean lateral, near-gap seagrass percent cover and the leaf length indicated a strong dependence of the state of the canopy on temporal hydrodynamic conditions, which in turn were impacted by the presence of the gap. Our results quantify the interactions between gaps and lateral meadow vegetation, highlight the structural impact of traditional moorings and support improved management and conservation of seagrass meadows.

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Section: Discussionsupporting

confidence: 84%

Impact of anthropogenically created canopy gaps on wave attenuation in a Posidonia oceanica seagrass meadow

Colomer¹,

Soler²,

Serra³

et al. 2017

Mar. Ecol. Prog. Ser.

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“…Sites with high silt content usually have a low diversity of species, while sites with coarse sediment particles have a much richer diversity of species (Thrush et al, ). As El Allaoui et al () pointed out, the presence of edges in canopies has been found to modify the hydrodynamics of the system, presenting a behavior that is neither that of the fully vegetated or the nonimpeded cases, but rather falls between. Ricart et al () also found that edges within a canopy change the sedimentary pattern, and they point out the importance of hydrodynamics to explain sediment pattern distribution.…”

Section: Discussionmentioning

confidence: 99%

“…These gaps may have both natural and/or human origins. For example, storms directly or indirectly may erode mattes by tearing whole sections away or scouring out their sediments, while laying cables or pipes in sea canopies favors the formation of gaps and changes the hydrodynamics in the canopy (El Allaoui et al, ). The persistence of coastal wetlands depends on the sediment deposition that controls the vertical position of the salt marsh surfaces (Bell et al, ).…”

Section: Introductionmentioning

confidence: 99%

Fragmented Canopies Control the Regimes of Gravity Current Development

2018

Self Cite

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Coastal ecosystems (marine littoral regions, wetlands, and deltas) are regions of high biological productivity. However, they are also one of the world's most threatened ecosystems. Wetlands are characterized by aquatic vegetation adapted to high salinity levels and climatic variations. Wetland canopies buffer these hydrodynamic and atmospheric variations and help retain sediment by reducing current velocity during sea storms or runoff after periods of rain. This work focuses on the effect of the presence of a gap (i.e., nonvegetated zone) parallel to the direction of the main current has on the sedimentation and hydrodynamics of a gravity current. The study aims to (1) address the behavior of a gravity current in a vegetated region compared to one without vegetation (i.e., the gap), (2) determine the effect gap size has on how a gravity current evolves, and 3) determine the effect gap sizes have on the sedimentary rates from a gravity current. Laboratory experiments were carried out in a flume using four different sediment concentrations, four different canopy densities (884, 354, 177, and 0 plants·m−2) and three different gap widths (H/2, H, and 1.5H, where H is the height of the water). This work shows that a gravity current's evolution and its sedimentary rates depend on the fractional volume occupied by the vegetation. While current dynamics in experiments with wider gaps are similar to the nonvegetated case, for smaller gaps the dynamics are closer to the fully vegetated case. Nonetheless, the gravity current exhibits the same behavior in both the vegetated region and the gap.

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“…As a result, Luhar et al (2008) suggest that fragmented meadows are more likely to persist in current-dominated environments, because of the enhanced current feedback within canopy gaps, than in wave-dominated environments, where there will be a tendency toward homogeneity because of this lack of feedback. El Allaoui et al (2015Allaoui et al ( , 2016 reported flume experiments in which waves interacted with gaps aligned perpendicular and parallel to the wave direction, simulating sagittal channels that form perpendicular to coastlines in seagrass canopies due to currents transporting waters mixed near the shoreline seaward. They found that, for both types of gap, wave velocity increased over the gap compared to the canopy and that denser canopies attenuated both wave velocity and turbulent kinetic energy within adjacent gaps, compared to sparser canopies.…”

Section: Two-dimensional Patch and Gap Simulationsmentioning

confidence: 99%

Biophysical Interactions in Fragmented Marine Canopies: Fundamental Processes, Consequences, and Upscaling

Folkard

2019

Front. Mar. Sci.

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Spatial fragmentation is a near-ubiquitous characteristic of marine canopies. Biophysical interactions with fragmented canopies are multi-faceted and have many significant implications at multiple scales. The aims of this paper are to review research on biophysical interactions in fragmented marine canopies, identify current gaps in knowledge and understanding, and propose ways forward. The review starts at the patch/gap scale and focuses initially on hydrodynamic interactions. It then considers the consequences of these interactions for particulate and dissolved material, and distributions of canopy-associated organisms. Finally, it addresses issues of upscaling to landscape-scale and ways in which this research can be applied to marine landscape management. Work on a broad range of canopy types is considered, including micro-algal biofilms and turf algae; macro-algae, seagrasses and coral reefs; saltmarsh vegetation and mangroves. Although the focus is on marine canopies, insights from studies of fragmented canopies in other contexts are drawn on where relevant. These include freshwater environments and terrestrial forests, grasslands, crop canopies, and urban areas. Specific areas requiring greater attention are highlighted. As a result of this meta-analysis, the following recommendations are made for further research. A lack of basic data is identified across all canopy types regarding the formation, fate and spatial and temporal characteristics of canopy patches, gaps, and spatial structure. Studies of hydrodynamics with fragmented canopies would benefit from shifting focus toward more non-uniform, realistic configurations, while ecological research in this area would benefit from a move toward configurations that are more controlled and tractable for quantitative modeling. More comparative studies across canopy types would enable understanding of their biophysical interactions and their consequences to be more fully tested and developed. A greater incorporation of chemical aspects of canopy systems into work that has hitherto focused on biophysical interactions would also be pertinent. Upscaling of patch and gap-scale phenomena to landscape-scale is identified as a crucial topic, since it is at the latter scale that management efforts are most readily carried out. Overall, an approach that balances hydrodynamics, marine canopy ecology, spatial analysis of landscapes, biogeochemistry, and socio-environmental interactions is recommended.

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Modified hydrodynamics in canopies with longitudinal gaps exposed to oscillatory flows

Cited by 17 publications

References 29 publications

Impact of anthropogenically created canopy gaps on wave attenuation in a Posidonia oceanica seagrass meadow

Impact of anthropogenically created canopy gaps on wave attenuation in a Posidonia oceanica seagrass meadow

Fragmented Canopies Control the Regimes of Gravity Current Development

Biophysical Interactions in Fragmented Marine Canopies: Fundamental Processes, Consequences, and Upscaling

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