Current- and wave-driven flow and nutrient exchange in natural and model submerged vegetated canopies
Abstract/Contents
- Abstract
- In the coastal ocean, seagrass canopies attenuate near-bed current velocities and modify flow in the region above. In so doing, they help to reduce sediment erosion and resuspension. Vertical profiles of mean water velocity and key turbulent quantities have characteristic features that indicate these underlying dynamics. While such profiles have been especially studied well in the laboratory, detailed measurements are rare in natural seagrass canopies. We addressed that deficiency with a comprehensive set of natural canopy flow measurements, analyzed in the context of the laboratory-derived models. Seagrasses depend on these hydrodynamic interactions for their health and basic biological functions. The rates of many of their core metabolic processes are limited by nutrient availability; in many environments, availability is constrained most by the slow diffusive transfer across element boundary layers. Boundary layer thickness is reduced by flow, and evidence has shown that seagrass nutrient uptake rates rise as mean water velocities are increased. However, uptake rates are enhanced even more significantly in wave-driven, oscillatory flows - flows that are less effectively attenuated within the canopy space. In another portion of the work described here, we measured flow-modulated seagrass community uptake directly in both current-driven and wave-driven flow. We found that uptake rate efficiency depends not just canopy depth-averaged flow magnitude, but also on the characteristic wave frequency. Finally, we found that at some field locations, flexible canopy-forming seagrasses were complemented with a dense understory of secondary species. In wavy-environments, understory biomass may fill distinct ecological niches while also helping to protect the bed from wave-driven disturbances. We created a simple numerical model to encapsulate the theory, and tested it in the laboratory with a collection of heterogeneous canopy mimics. Results supported the idea that understories may indeed significantly alter near-bed hydrodynamics.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2013 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Weitzman, Joel Samuel |
|---|---|
| Associated with | Stanford University, Department of Civil and Environmental Engineering. |
| Primary advisor | Koseff, Jeffrey Russell |
| Thesis advisor | Koseff, Jeffrey Russell |
| Thesis advisor | Fong, Derek |
| Thesis advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Thesis advisor | Monismith, Stephen Gene |
| Advisor | Fong, Derek |
| Advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Advisor | Monismith, Stephen Gene |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Joel Samuel Weitzman. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Ph.D. Stanford University 2013 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2013 by Joel Samuel Weitzman
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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