Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (p. [137]-142). Also available in print.

Exposed sand beaches are increasingly under pressure from human population growth and recreation. Activities, such as vehicle driving and horse riding, can pose a significant threat to specialist fauna living in the sediment. Few studies have evaluated how vehicles affect sand beach fauna and none have examined the impacts of horse users on burrowing bivalves. The research questions addressed were: do vehicles and/or horses on sand beaches impact on intertidal shellfish populations? Following on from this, can management policies mitigate any negative impacts from such activities on sand beaches? This research required an interdisciplinary approach utilising methodologies from coastal geomorphology, biological science and management. The intertidal distribution of the New Zealand surfclam Paphies donacina (southern tuatua) determined seasonally on six exposed surf beaches along Pegasus Bay. The impacts of vehicle and horse users on shellfish survival were experimentally investigated, and novel in situ methods were developed to examine the effects of horses on bivalve survival. Intertidal tuatua were small (< 30 mm) and shallowly buried. Found approximately 30 m below the last high tide line, they may be exposed to vehicle and horse users. There was a positive linear relationship between the number of vehicle passes and tuatua mortality (% tuatua mortality = 4.8 + 0.23 x number of vehicle passes). On average, horse riding resulted in 36.9% tuatua mortality within a single hoof print, but walking resulted in lower mortality than trotting or galloping. Extrapolative modelling predicted that the long-term presence of these users would be highly detrimental to shellfish. Reducing the temporal frequency and spatial extent of vehicle and horse users on sand beaches could decrease shellfish mortality. The thesis results were used to evaluate current management techniques and provide management options to minimise the potential impacts of beach users on shellfish resources.

The prediction of morphological responses of natural and engineered beaches to the prevailing wave, tide and wind conditions continues to be a challenge due to the wide variability in site conditions and the underlying complexities of the processes involved. For this reason, field measurements, especially with a good spatial and temporal resolution, play a critical role in monitoring the performance of intervention work. This thesis presents the results of a five-year study at Aberdeen beach on the North Sea coast of the UK, with the aim of obtaining and analysing high-quality field measurements of beach dynamics before and following beach nourishment and the installation of nearshore breakwaters. Beach topographic data were collected between June 2006 and July 2011 at approximately monthly intervals using real time kinematic GPS, augmented by Argus video monitoring. An assessment of the horizontal and vertical errors of the Argus system found it to be comparable to other similar installations. The initial response of the area of beach subject to recent intervention works was the formation of stable bays in the lee of the nearshore structures, making this zone morphologically distinct from other areas of the beach. Time-synchronous wave data was collected from nearshore wave buoy measurements, or derived from transformed Met Office model-predicted wave data, and were considered in relation to the timing of beach morphology responses to the prevailing wave conditions. A strong link was observed between the 30-day average wave height and the beach dynamic, with erosion commencing when Hm0 rose above 1 m, and antecedence being an important factor in beach response to successive winter storm events. The data and insights from the present study can be used to develop better predictive models and coastal monitoring strategies. Future studies seeking to further understand beach response would benefit from the ability to capture variation within tidal cycles, and to be able to connect the beach to wider nearshore and offshore bedforms and marine processes.

The BEACH family proteins are conserved in all eukaryotes and are important for membrane trafficking. Defects in specific BEACH proteins have been linked to severe human disorders. For example, loss of human LYST protein causes the Chediak-Higashi Syndrome (CHS), a lethal disorder that affects lysosomal function. I postulate that different classes of BEACH proteins contribute distinct cellular functions in specific organelles. Based on this functional specificity, I hypothesize that each class of BEACH proteins must localize to their respective organelle where they are known to function. Unfortunately, the localization of most mammalian BEACH proteins is not known and no localization signal has been determined for any BEACH protein. Previous work showed that the Dictyostelium LvsA protein localizes and functions on the contractile vacuole while LvsB localizes and functions on the lysosome. Thus, Dictyostelium is a good model system to understand how BEACH proteins localize to specific organelles. Using a knock-in approach and parasexual techniques, I generated a collection of LvsA truncation mutants tagged with GFP and expressed them in different cell lines. Hence I can test the ability of each mutant protein to localize on contractile vacuoles by fluorescence microscopy. I show here that LvsA requires two regions to localize on the contractile vacuole: the N-terminal 140-457 amino acids and the BEACH. In addition, the expression of the N-terminal 651 amino acids of LvsA causes a dominant negative effect suggesting a possible functional protein-protein interaction within this region. Furthermore, sequence alignment analysis shows that this N-terminal region is only conserved within each class of BEACH family proteins. This finding supports our hypothesis and suggests that diversity within the N-terminal region may be due to the specialized targeting sequences of each class of BEACH proteins. Taken together, these results suggest that the conserved BEACH domain may serve as a general localization sequence while the N-terminal segment is responsible for targeting these proteins to their distinct organelles. This study will facilitate the identification of localization signals in other BEACH proteins which is important to dissect the molecular mechanism of their respective functions. / text

published_or_final_version / Geography and Geology / Master / Master of Philosophy

No description available.

On sandy coastlines dunes provide a barrier of protection from strong environmental forces that can naturally occur during storm events including storm surges that expose the dunes to large waves. A set of laboratory experiments were used to investigate the morphological processes during the erosion of a steep dune face under bichromatic wave conditions for two different mean water level elevations, corresponding to storm surges and waves that collide with or overwash the dune. In the collision regime, episodic slumping due to the undercutting of the dune resulted in sudden erosional events followed by long periods of wave-driven reshaping at the dune toe. In the overwash regime, dune erosion was faster and occurred at a more consistent rate. Small scale bedforms (ripples) measured during the overwash test evolved in height faster and to greater overall heights than collision test while bedform lengths were not affected by the change in water level. A numerical model, XBeach, was calibrated to examine the ability to predict erosion of the steep dune due to waves in the two water level regimes. XBeach was not able to recreate the spatial variability of the significant wave height profile from the laboratory measurements; however, mean velocities were in good agreement with observations suggesting that bed shear stress is well estimated. During mobile bed simulations of erosion in the two regimes, the model was in agreement with measured dune erosion after initial adjustment. XBeach was very sensitive to several parameters that control the rate of erosion including the critical avalanching slope under water, the threshold water depth and the sediment transport formulation. The model did not perform well at predicting erosion rates until these parameters had been modified. Overall, XBeach performed better when simulating dune erosion in the overwash regime than the collision regime. / Thesis (Master, Civil Engineering) -- Queen's University, 2014-04-01 14:54:35.257

No description available.

The continuous monitoring of beaches and structures near, or in the surf-zone, has become a vital task from an environmental and economic standpoint. Specifically, the Durban beaches are continually nourished with sand that is dredged south of the Durban Harbour mouth. Constant monitoring is essential to control the erosion and accretion of these beaches. Currently, infrequent and labour-intensive manual surveys are being used to fulfil this task. This dissertation describes the techniques used to process and validate surf-zone video images to extract information, which is equivalent but more frequent and cost effective to that obtained using manual surveying methods. The emphasis is on the extraction of accurate hourly waterlines by analysing video images obtained from Coastal Imaging stations located at Addington Beach and North Beach in Durban, South Africa and the measurement of rip currents in the surf-zone from video images together with the validation of these results. The implementation of a neural network incorporating non-local image pixel data is more reliable than previously used methods, for example, grayscale thresholding or the delta-discriminator. Grayscale thresholding relies on the difference between the water and the sand pixel intensities. The delta-discriminator incorporates hue-saturation-lightness (HSL) values to improve the discrimination between water and sand. These methods could not, however, overcome the problem of varying seasonal and diurnal light intensities and require the prior choice of threshold values. The use of non-local data, such as the average RGB-values, in addition to individual pixel values as inputs to a neural network is shown to give better results in changing ambient lighting conditions. Wavelet and Fourier analysis of the temporal nature of the breaking waves in the surf-zone is also used to calculate more accurate waterlines. These extracted waterlines are validated by data collected from manual surveys. The use of Digital Correlation Image Velocimetry (DCIV) has been proven as a successful method in tracing velocity flow fields in a fluid medium. Typically, the medium is populated with distinct seeds that are tracked through successive video frames using a cross-correlation technique. It is shown that DCIV can be used in surf-zone images to measure surface rip currents by tracking the structure of the advected foam. This technique was validated by simultaneously tracking a large number of yellow corks scattered on the water surface. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

No description available.