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Water Flow in Seagrass Ecosystemskeulen@murdoch.edu.au, Michael van Keulen January 1998 (has links)
Water motion has been shown to influence almost every aspect of the ecology of seagrass communities; seagrass communities have likewise been shown to significantly influence water movement around them. This thesis examines the important role of water motion on seagrass ecosystems by integrating field and laboratory studies of several aspects of seagrass ecology influenced by water motion.
To facilitate the study of hydrodynamics of seagrass ecosystems, a solid state electronic current meter was designed and developed, using thermistors as flow sensing devices. Important characteristics of the meters include: no moving parts, compact size, high sensitivity (resolution
better than ± 0.5 cm s-1), and high sampling rate (greater than 0.2 Hz). Deployment of the meters in field measurements provided reliable and meaningful results of flow conditions through seagrass canopies, and they show great potential for use in many studies of marine ecology.
Field studies of water velocity profiles revealed significant differences between the shapes of profiles of different seagrass species, particularly between species of Posidonia and Amphibolis. Of particular note is the observation of a region of high water velocity beneath the leafy canopy of Amphibolis, which was not present in the Posidonia plants.
Water velocity profile measurements, sediment grain size analyses and standing stock measurements were conducted across an exposure gradient in a Posidonia sinuosa meadow.
These studies revealed that, while the exposed location experienced a higher ambient water velocity than the sheltered site, the baffling influence of the seagrass canopy reduced the water velocity to approximately the same at both sites, within the meadow, although the effects varied seasonally. It was also observed that the seagrass meadow produced apparent skimming flow under the low flow conditions measured at the sheltered location; this phenomenon reflects the capacity for flow redirection over the canopy, and has important implications for the sub-canopy ecosystem and the protective role of seagrasses on the seabed.
Field and laboratory studies on the role of seagrass density on the hydrodynamic nature of seagrass ecosystems revealed that water velocity profiles through meadows of reduced densities, and different shoot arrangements, were markedly different to natural profiles, implying the
existence of a critical density (approximately 25 % of natural meadow density) with regard to canopy hydraulics.
The role of water motion at an individual leaf scale was investigated with a series of laboratory flume studies of photosynthetic rates of seagrass and algae. The results show that the response of photosynthetic rate to water velocity depends very much on the plant species, with the algae markedly more productive (on a unit chlorophyll basis) than the seagrasses tested. Increases in
photosynthetic rate were observed at water velocities above approximately 2.5 cm s-1; negligible photosynthetic activity was observed below this velocity. Calculation of P v. I curves indicated that the Posidonia species had high Ik values at low velocities (1360 :mol quanta m-2 s-1 for P. australis and 250.8 :mol quanta m-2 s-1 for P. sinuosa at 1.58 cm s-1), which decreased with increasing water velocity (to 138.9 and 24.77 :mol quanta m-2 s-1 for P. australis and P. sinuosa respectively), while the algal species had relatively constant values of Ik across all water velocities (85.42 to 312.7 :mol quanta m-2 s-1 for Ulva lactuca and 169.7 to 573.9 :mol quanta m-2 s-1 for
Laurencia cruciata). Dye visualization studies showed that the algae remained quite rigid at all the velocities tested, while the seagrass leaves compressed as velocity increased. This resulted in an increased rate of turbulence creation by the algae, which is believed to enhance photosynthetic rates, through improved nutrient exchange rates across the boundary layer adjacent to the thallus.
Further dye visualization studies revealed the significance of blade morphology on the creation of microscale turbulence at the surface of seagrass leaves. Epiphytic growth on seagrass leaves was observed to play an important role in breaking up water flow across the leaf surface, thereby enhancing the creation of microscale turbulence.
From these studies, it is clear that water motion influences all aspects of the functioning of all
components of seagrass communities, playing a role in nutrient supply, reproduction, physical stability, temperature and metabolic functions. The influence of seagrass meadows on coastal hydrodynamics is also apparent, with potential impacts on sediment stability, recruitment of benthic species and coastal erosion. This thesis has clearly demonstrated that water motion is
an important parameter in seagrass ecology, and requires serious consideration in seagrass research, conservation and rehabilitation programmes.
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Development and validity assessment of the Max Power Model for the detection, separation, and quantification of differences in resistive and propulsive forces in swimmingWhite, Joshua Childs. January 2006 (has links)
Thesis (Ph. D.)--Indiana University, 2006. / Includes bibliographical references (leaves 196-206). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.
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Numerical solution of quadratically non-linear boundary value problems using integral equation techniques : with applications to nozzle and wall flows /Goh, K. H. M. January 1986 (has links) (PDF)
Thesis (Ph. D.)--University of Adelaide, 1987. / Includes bibliographical references (leaves 140-142).
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On three-dimensional hydrodynamic numerical modelling of wind induced flows in stably stratified waters : a Galerkin-finite difference approach /Jung, Kyung Tae. January 1989 (has links) (PDF)
Thesis (Ph. D.)--University of Adelaide, 1989. / Includes bibliographical references (leaves 169-178).
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Simulation of hydrodynamics and sediment transport patterns in Delaware Bay /Celebioglu, Tevfik Kutay. Piasecki, Michael, Ph.D. January 2006 (has links)
Thesis (Ph.D.)--Drexel University, 2006. / Includes abstract and vita. Includes bibliographical references (leaves 143-150).
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Numerical study of nonlinear free-surface flows /Muthedath, Premkumar, January 1992 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 101-105). Also available via the Internet.
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Molecular dynamics simulations and microscopic hydrodynamics of nanoscale liquid structuresKang, Wei. January 2008 (has links)
Thesis (Ph. D.)--Physics, Georgia Institute of Technology, 2008. / Committee Chair: Landman, Uzi; Committee Member: Chou, Mei-Yin; Committee Member: Gao, Jianping; Committee Member: Glezer, Ari; Committee Member: Luedtke, W. D.
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The effect of prewetting on the residence time distribution and hydrodynamic parameters in trickle bed reactorsWales, Nadine Jenifer. January 2007 (has links)
Thesis (M.Eng. (Chemical Engineering)) -- University of Pretoria, 2007. / Includes bibliographical references.
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Trickle flow multiple hydrodynamic states the effect of flow history, surface tension and transient upsets /Van der Westhuizen, Ina. January 2006 (has links)
Thesis (M.Eng. (Chemical Engineering)) -- Universiteit van Pretoria, 2006. / Includes bibliographical references.
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Stochastic modelling of unsteady open channel flow and reliability analysis /Lu, Zhihua. January 2008 (has links)
Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 168-176). Also available in electronic version.
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