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Mitchell, John Dickerson. "Estuary Water Movement." W&M ScholarWorks, 1986. https://scholarworks.wm.edu/etd/1539617567.
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Tattersall, Graham Richard. "Tamar estuary sediment dynamics." Thesis, Bangor University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341218.
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Vromans, Deborah Claire. "Macrophyte phenology in a temporarily open/closed Estuary compared with a permanently open Estuary." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1393.
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Temporarily open/closed estuaries (TOCEs) are unpredictable environments that change in response to mouth condition, which is influenced by freshwater flooding or sea storm surges. The aim of the study was to determine whether macrophyte phenology in a TOCE was event driven rather than cyclically predictable and if it differed from permanently open estuaries (POEs). Macrophyte growth and flowering phenology in response to environmental conditions was investigated in the East Kleinemonde Estuary (TOCE) and the Kowie Estuary (POE) along the eastern coastline of South Africa. The lack of freshwater flooding due to low rainfall coupled with several overwash events resulted in a prolonged period of mouth closure from September 2008 to the end of this study period in 2010. This in turn caused the inundation of the supratidal and intertidal habitats, high water level (> 1.57 m amsl) and high salinity (30 - 42 ppt) in the TOCE. Principle Components Analysis showed that high water level and reduced sediments were the most significant environmental factors affecting macrophyte phenology. Macrophyte phenology in the POE was primarily driven by temperature, sediment redox potential and salinity. The saline high water level and reduced sediment significantly reduced macrophyte cover in all habitats in the TOCE. Macrophytes in the POE maintained high cover abundance due to seasonal re-growth compared to the TOCE where cover declined over the sampling period due to the high water level. Subsequent to water level dropping by as little as 11 - 20 cm in the TOCE, the intertidal species Sarcocornia tegetaria and Salicornia meyeriana completed their life-cycles and produced viable seeds within four and three months of germinating respectively. In contrast, the Sarcocornia hybrid and S. meyeriana in the POE took longer to complete their life-cycles, namely seven and nine months respectively, while S. tegataria did not germinate in situ but reproduced vegetatively despite producing seed. In the TOCE, the submerged species Ruppia cirrhosa and Chara vulgaris completed their life-cycles within five and three months and produced a maximum of 26 242 and 196 998 seeds m-2 respectively. Due to high water level and prolonged inundation, the reproductive periods were shorter for the intertidal and reed and sedge species in the TOCE compared to the POE. Seed output during the two reproduction periods varied between the two estuaries. Sarcocornia decumbens and S. tegetaria produced a substantially higher number of seeds in the TOCE compared to the POE, namely 0 - 102 847 versus 20 661 - 48 576 seeds m-²; and 7 001 - 45 542 versus 1 587 – 16 958 seeds m-² respectively. Seed output in the TOCE was significantly higher in S. tegetaria during the second reproduction period despite the significantly lower plant cover, which may be a function of the stressful environment in the TOCE. Seed production of S. meyeriana was significantly higher in the POE compared to the TOCE, with 264 224 - 640 292 compared with 24 050 - 27 643 seeds m-², due to higher plant cover in the POE. The research suggests that macrophyte phenology in the TOCE was significantly influenced by mouth condition. Further, macrophytes were able to demonstrate considerable phenotypic plasticity in response to changing and unfavourable environmental conditions. These data can be used in mouth management plans and freshwater requirement studies in TOCEs to ensure that macrophytes can complete their life-cycles and produce viable seeds for the safeguarding of habitat persistence and ecological processes. In impacted estuaries where artificial mouth opening is practised and the macrophytes have been severely degraded or extirpated, management should ensure that the intertidal and supratidal habitats are not inundated during peak flowering and seed production periods i.e. late spring to early autumn (November to March).
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Louw, Liezel. "The zooplankton of Mngazana estuary." Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/702.
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The zooplankton community of the main channel of the Mngazana estuary was investigated on six occasions over one year. Spatial and temporal variability in zooplankton abundance and distribution were sampled using two slightly modified WP2 plankton nets of 200 μm mesh and 57 cm mouth diameter. Nets were fitted with calibrated Kahlsico 005 WA 130 flow meters. A set of environmental variables were also measured at each site. The water column of the main channel of Mngazana estuary was stratified in summer but well mixed in winter. Temperature progressively increased from the lower stations to the upper reaches of the estuary. Maximum vertical temperature differences occurred in the middle estuarine reaches. Salinity progressively decreased from the lower reaches to the upper reaches, but was generally above 26 from Station 3 to Station 8. Only during November 2005, were salinity readings low due to heavy rains. Summer salinity values were always lower than the winter salinity values as a result of summer rainfall. A total of 76 zooplankton taxa were identified. The estuarine copepods Acartia natalensis and Pseudodiaptomus hessei dominated the assemblage, with maximum abundances in the middle to upper reaches. Acartia natalensis reached high densities in winter (> 50 000 m-3) although lowest abundances were recorded when maximum rainfall was received (November 2005). Wooldridge (1977) and Deyzel (2004) recorded maximum densities during summer. Pseudodiaptomus hessei reached high densities (> 17 000 m-3) during the highest rainfall month. Previous studies indicated that this pioneer species is able to recover quickly after a flood and subsequently increase rapidly in numbers. The mysid, Mesopodopsis africana reached high densities (> 5 000 m-3) in the middle estuarine reaches during summer. Ichtyofauna, brachyura and anomura were important contributors to the merozooplankton component of the community. The maximum number of species was recorded during winter in the lower estuarine reaches, when vertical differences in salinities were minimal.
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Pritchard, William James. "Anammox in a temperate estuary." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8852.
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The seasonal variation of anammox is yet to be comprehensively studied, unlike denitrification, the more traditional sink for fixed nitrogen. A seasonal study of anammox, denitrification and benthic oxygen consumption using the revised isotope pairing technique is presented in Chapter 2. Experimental temperature and NO3- concentration were kept constant throughout so that the capacity of the sediment for anammox could be estimated. Similar seasonal variations in the rates of anammox, denitrification and oxygen consumption suggest that anammox is controlled by the availability of organic carbon. Furthermore the effect of tidal inundation by overlying water rich in NO3- was investigated by measuring rates of anammox, denitrification and oxygen consumption at three tidal elevations throughout the year. A significant relationship between anammox and denitrification was established at each tidal elevation, which increased in strength as length of inundation decreased. To complement this seasonal study, additional experiments were undertaken, which are described in Chapter 3, to determine how anammox, denitrification and sediment metabolism responds to variations in experimental NO3- concentration and temperature. There were significant increases in rates of anammox, denitrification and sediment metabolism with temperature until 20oC when rates of anammox began to reduce. Furthermore there was significant variation in the response of all three processes to temperature in samples collected at different dates, which suggested that reduced bioavailability of organic carbon in the winter months was limiting the response to temperature. In addition to exploring how inorganic N is cycled in estuarine sediments, the ability of estuarine sediments to oxidize urea via nitrite was examined using 15N and 13C labelled substrates. Results, which are presented in Chapter 4, indicate that urea added to anaerobic sediment slurries was rapidly hydrolysed to ammonium before being oxidized via the anammox pathway.
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Monteiro, Marcela Cunha. "Natural and anthropogenic control of water quality of an Amazon estuary : the Caeté estuary (Brazil)." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/406005.
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In the Amazon region, few data are available on the impacts caused by the urban settlements found in the proximity of estuaries. In the estuary of the Caeté River, the focus of the present study, the nutrient input is controlled by both natural features and anthropogenic disturbances generated by local communities. In this context, the principal aim of the study was to analyze the quality of the water of the Caeté estuary, and the relative contribution of natural and anthropogenic forcings. To this end, climatological, hydrodynamic and hydrological features were monitored, and potential sources of pollution were identified in the different sectors of the Caeté estuary. Potential future scenarios for the estuary are also described, based on the analysis of anthropogenic and natural processes, which may contribute to the quality of its waters. The results indicate higher levels of nutrient input in the upper sector of the estuary, where 90% of the local population is concentrated, and most of the region's commercial activities (e.g., public markets, ice factories, and docking facilities) are found. As a consequence, eutrophic waters with high concentrations of faecal coliforms (up to 1100 MPN/100 ml) were observed during spring tides in the dry season when the transport and dilution of the estuary's waters are less effective. Eutrophication also occurred to a lesser extent in the other (middle and lower) estuary sectors, although in this case, the results indicate the influence of natural processes, reflecting the high nutrient concentrations of this Amazonian region. During neap tides, eutrophication was less pronounced, and water quality was improved in both dry and rainy seasons. A comparative analysis showed that, under similar conditions of the flood cycle, the trophic status of the estuary varied little between spring and neap tides. As the population of the region surrounding the Caeté estuary is increasing by 10-20% per decade, resulting in a significant increase in human pressures and impacts on the study area. The current eutrophication status of the estuary may have permanent effects, which may be aggravated during the dry season or drought events, when the estuary is more vulnerable to the retention of nutrients. The water quality of the Caeté Estuary can be improved by the implementation of the following measures: (i) urban planning to control the discharge of sewage, (ii) the construction of water treatment plants to reduce the input of untreated effluents, and (iii) the introduction of regulations for the use of water based on its current quality.Los impactos más frecuentes en los estuarios se deben a los asentamientos urbanos no planificados. Como consecuencia de dichos asentamientos, los estuarios se han visto expuestos a una serie de perturbaciones ambientales, tales como el incremento en la entrada de nutrientes y cambios en los usos del suelo y en la hidrología local. En el estuario del río Caeté, objeto de este estudio, las perturbaciones antrópicas originadas en las comunidades de alrededor del estuario y el funcionamiento natural del sistema controlan el input de nutrientes en el estuario. El objetivo principal de esta tesis es analizar la calidad del agua del estuario del río Caeté y la influencia de las forzantes naturales y antrópicas que actúan en él. Para tal efecto, los aspectos climáticos, hidrodinámicos e hidrológicos fueron monitorizados y se identificaron las fuentes potenciales de polución en el estuario. Además, se describieron una serie de potenciales futuros escenarios para el estuario basándose en los procesos naturales y antrópicos que pueden afectar la calidad del agua en las próximas décadas. Los resultados muestran que el input de nutrientes disueltos es mayor en el sector superior del estuario, que concentra el 90% de la población local y tiene una alta incidencia de actividades comerciales (mercados públicos, fábricas de hielo, astilleros, entre otros). Como consecuencia, se observaron aguas eutróficas con altas concentraciones de coliformes fecales (até 1100 NMP/100 ml) durante las mareas vivas en la estación seca, cuando el transporte y/o dilución son menos efectivas. La eutrofización, aunque menos pronunciada, también ocurrió en el resto de sectores (medio y bajo estuario). Sin embargo, estos resultados parecen indicar que esto puede deberse a una condición natural de la región amazónica, la cual es naturalmente enriquecida con una elevada cantidad de nutrientes. Durante mareas muertas, la eutrofización fue menos pronunciada y la calidad de agua presentó mejores condiciones en todas las estaciones monitorizadas. El análisis comparativo ha mostrado que bajo condiciones similares (marea llenante) el estado trófico entre mareas vivar y muertas presenta similitudes. Considerando que la población se incrementa entre 10 y 20% por década en la región, esto puede resultar en un incremento significante de la presión humana y del impacto alrededor del estuario. En este caso, el estado eutrófico observado actualmente podría afectar el estuario de manera permanente. La situación podría agravarse durante la estación seca o eventos de sequía, cuando el estuario es más susceptible a retener los nutrientes. Con el objetivo de mejorar la calidad del agua, se podrían implementar ciertas medidas en el estuario del Caeté basadas en (i) planeamiento urbanístico para controlar la descarga de efluentes en el estuario (ii) construcción de una estación de tratamiento de agua para reducir la entrada de efluentes no tratados y (iii) regular los usos del agua del estuario en función de la calidad de agua.
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Ibrahim, Zelina Zaiton. "An integrated approach to the investigation of an equatorial estuary : the Klang River Estuary, Malaysia." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328682.
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Moore, Rowena Deborah. "Hydrodynamic and Morphometric Modelling of a Macro-Tidal Estuary : The Dee Estuary of NW England." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511030.
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Koroknay, Brittani J. "Quantifying Watershed Loads to a Low Relief, Coastal Plain Estuary, the New River Estuary, N.C." W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539617915.
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Watershed modeling is an important tool for quantifying the inputs of fresh water, sediments, and nutrients into receiving estuaries and potential changes in those loads under scenarios including changes in land use and climate. There are a variety of existing watershed loading models available, from simple to complex, but a spectrum of these models have yet to be applied and compared in a low relief, coastal plain setting. This project has been conducted as part of the Defense Coastal/Estuarine Research Program (DCERP), which has focused on the impact of Marine Corp Base Camp Lejeune (MCBCL) and activities in the surrounding watersheds on the New River Estuary (NRE), located in southeastern North Carolina. As part of DCERP, nine sub-watersheds on MCBCL with contrasting land use were monitored to allow computation of freshwater, sediment, and nutrient loads to the NRE. In the current project, these loads were used to assess the performance of two existing watershed models using the Environmental Protection Agency’s (EPA) Better Assessment Science Integrating point and Nonpoint Sources (BASINS) 4.0 modeling suite: the relatively complex, temporally-resolved Hydrologic Simulation Program-Fortran (HSPF), and the relatively simple, annually-resolved Pollutant Loading (PLOAD) model. For both models, the 2001 National Land Cover Data were used for analysis; this dataset was compared to the recently released 2006 NLCD dataset and changes were found to be small. Monthly HSPF model output generally followed precipitation trends, and tended to over-predict freshwater stream flow and under-predict sediment and nutrient loads. PLOAD reproduced annual loads of total nitrogen within measured ranges, under-predicted annual loads of total suspended solids, and was less successful at predicting PO43- loads. Results from HSPF and PLOAD were combined with those from six other modeling approaches applied during DCERP to complete a spectrum of models from simple to complex. Model output from HSPF and PLOAD was scaled up to estimate loads entering the NRE from that portion of its watershed lying on MCBCL. Model estimates suggest that approximately 5-6% of the total nitrogen entering the NRE from external sources originates from the MCBCL watershed, a value on the lower end but within the range of estimates from other models applied to the system. Scenarios were run within HSPF to investigate how the conversion of forested land to impervious surfaces on MCBCL may alter existing loads; the model was relatively insensitive to changes in impervious surfaces. Neither PLOAD nor HSPF predicted nitrogen, phosphorus, and sediment loads better than the other watershed models applied during DCERP. The results of this study combined with development of other models suggest that simpler models, such as PLOAD, are able to estimate loads to the NRE as well as more highly technical models, such as HSPF, and that regardless of model choice a focus on loads at the annual scale is most justifiable.
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Chan, Terence. "Phytoplankton dynamics in a seasonal estuary." University of Western Australia. Centre for Water Research, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0089.
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[Truncated abstract] The Swan River is a highly seasonal estuary in the south-west of Western Australia. Salinity may vary from fresh to marine at various times throughout the estuary, depending mostly on the intensity of freshwater discharge. There are occasional problematic dinoflagellate blooms which have spurred investigation of the dynamics of the phytoplankton community. The objective of this research was to examine how phytoplankton biomass and species' successions are influenced by the multiple variables in the aquatic ecosystem, and, if possible, to determine the dominant factors ... Comparisons of phytoplankton nutrient limitation simulations with experimental observations from field bioassays require further investigation, but reinforce findings that nutrients may only limit phytoplankton biomass when there is a convergence of favourable hydrological and hydrodynamic conditions. The Swan River estuary has undergone substantial hydrological modifications from pre-European settlement. Land clearing has increased freshwater discharge up to 5- fold, while weirs and reservoirs for water supply have mitigated this increase and reduced the duration of discharge to the estuary. Nutrient loads have increased approximately 20-fold from pre-European levels. The individual and collective impacts of these hydrological changes on the Swan River estuary were examined using the hydrodynamic-ecological numerical model. The simulation results indicate that despite increased hydraulic flushing and reduced residence times, increases in nutrient loads are the dominant perturbation, producing increases in the frequency and biomass of blooms by both estuarine and freshwater phytoplankton. By comparison, changes in salinity associated with altered seasonal freshwater discharge have a limited impact on phytoplankton dynamics. Reductions of nutrient inputs into the Swan River estuary from its catchment will provide a long-term improvement in water quality but manipulations of freshwater discharge have the potential to provide a provisional short-term remediation measure allowing at least partial control of phytoplankton bloom potential and eutrophication.
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Reeve, Glen M. D. "Sedimentation And Hydrodynamics of Whitianga Estuary." The University of Waikato, 2008. http://hdl.handle.net/10289/2344.
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Whitianga Estuary is a bayhead barrier type estuary located on the east of the Coromandel Peninsula, North Island, New Zealand. The catchment has undergone many land-use changes since pre-European settlement. In some areas of the catchment land-use has changed from native forest to grasslands to forestry and back to pasture. These changes in catchment land-use all contribute to increased sedimentation into the estuary. Development of the estuary itself has also occurred in recent times. Much growth has been focussed around the estuary due to Whitianga town-ship having a large boating community, and includes a 170 berth marina and wharf situated at the tidal inlet entrance to the estuary. These, and the extensive canal development engineering works can have substantial impacts on the sedimentation regime, and may modify tidal circulation, flushing, and sediment deposition within the estuary. The principle aim of this research is to assess hydrodynamics and sedimentation of the estuary for future management and development purposes, and also to model different scenarios in order to determine the most cost effective, and least obtrusive design for a proposed boat-ramp and approach channel near the marina. To determine sedimentation rates, sediment cores from four locations were collected to depths of 1 m. Coring locations were chosen based on preliminary model run results, selecting areas that appeared to be long-term sediment sinks of a stable nature. Cores were divided into 10 mm sections and prepared for 210Pb dating and heavy metal analysis, to make an assessment of the vertical sedimentation rates. Recent sedimentation rates were found to be as high as 9 mm/yr post-1950s and past sedimentation rates as high as 30 mm/yr pre-1950s. The use of heavy metal analysis for dating proved difficult as the background levels of the conservative elements used to normalise results varied, making the geochemical analysis approach inappropriate. As bathymetry is one of the most important aspects of modelling, a large amount of surveying was undertaken for this study. LiDAR, singlebeam data, and recent rectified aerial photographs were interpreted for the creation of a bathymetric grid file to be used for hydrodynamic modelling of the estuary. The 3DD numerical model was used to determine tidal flows and current velocities. From this initial hydrodynamic model a particle-tracking model was created to determine sediment transport pathways within the estuary. From the initial 20 m model it was then possible to create a number of nested model grids for the purpose of determining the best practice scenario for the creation of a proposed boat ramp and associated approach channel near the harbour entrance. Hydrodynamic results suggest that residual circulation in Whitianga Estuary is nearly in balance, with a low ebb tidal domination present. Particle tracking results suggest that sediment entrained and carried into and within the estuary will accumulate on the intertidal flats. Sediment transport modelling indicates that the impact of a proposed boat-ramp will result in sedimentation of the dredged approach channel due to reductions in residual and tidal velocities.
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Beckett, C. L. "Heavy metals in Severn Estuary ecosystems." Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373733.
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Бондаренко, Юлія Станіславівна, Юлия Станиславовна Бондаренко, Yuliia Stanislavivna Bondarenko, and Ю. С. Коваленко. "Estuary - як останній стандарт англійської вимови." Thesis, Вид-во СумДУ, 2010. http://essuir.sumdu.edu.ua/handle/123456789/16418.
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Ramirez, Mendoza Rafael. "Flocculation controls in a hypertidal estuary." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2010209/.
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Estuaries are ephemeral geological formations in constant change, which is being accelerated by human intervention. Fine sediments are an important characteristic of estuarine systems upon which anthropogenic and natural activities depend. An important feature of fine sediments is their cohesiveness, following which individual particles aggregate into the so-called flocs or break-up due to turbulent motions. Throughout the flocculation process (aggregation and break-up), flocs change their properties of size, density and settling velocity with consequences on suspended sediment transport, primary productivity and contamination. The prediction of possible changes in flocculation represents an important tool to help in decision making. Although some knowledge has been gained from laboratory and field investigations, the behaviour of the flocs in real conditions is still not well understood. Even though formulations to describe changes in floc dynamics have been proposed, there is a wide disparity between studies. The aim of this research is to contribute to the knowledge of the flocculation process and propose novel methods for the implementation in numerical models, via a case study in the Dee Estuary. The Dee is a hypertidal Estuary located in Liverpool Bay, with surface tidal currents over 1 m/s. The effects of turbulence generated by the strong tidal currents and waves on floc properties are of particular interest. The possibility of a simple formulation for the flocculation process is also investigated in order to be implemented in a state of the art coupling of hydrodynamic (POLCOMS), turbulence (GOTM) and waves (WAM) numerical models. To achieve these objectives, hourly data of grain size, volume concentration and current velocity from a mooring deployed in the Welsh Channel and water samples from a research vessel taken from 12 February to 9 March on 2008 have been used. The high sampling rate for the currentv elocities enables the calculation of turbulent stress, turbulent kinetic energy, shear rate, Kolmogorov microscale and dissipation. Mass concentrations were obtained froma series of water samples collected from a research vessel during the 12-14th February 2008, which were used to convert volume concentration into mass concentration. Three hydrodynamic regimes have been distinguished from the observations: “current only” (negligible effect of waves), “combined currents-waves” (important effects from both forcings) and “wave dominant”. Quarter-diurnal variability of floc size was present during the first two regimes. Observations showed aggregation of flocs during periods of low turbulence with higher magnitude during low water slack than during high water slack. Break-up occurred concurrently with high turbulence periods during flood and ebb phases with higher magnitudes after ebb. Differences are likely due to turbulent stress asymmetries related with mixing and periodic stratification even though freshwater input was low. The “current only” regime was used to investigate the changes in floc settling velocities in relation with turbulent stress. A simple semi-empirical formulation was proposed and implemented in the numerical models. This expression depends on a single variable, which can be obtained from the turbulence model, and is both physically and mathematically correct. Model results qualitatively reproduced the neap-spring variability and the quarter-diurnal variability of floc settling velocities and suspended sediment concentration. During the “combined currents-waves” regime, waves were tidally modulated and led to enhanced aggregation and break-up, with higher floc size range than during the “current only” regime. Wave tidal modulation and quarter-diurnal variability of floc size were lost when waves were dominant. Flocs sizes exhibited a low range related to wave height. Inverse relationships between turbulent properties and median grain size were found for the three regimes, with higher scatter of data for the Kolmogorov microscale and shear rate due to different floc behaviour during flood and ebb phases. Turbulent kinetic energy showed a better relationship with floc size, which suggests its use as a floc size predictor instead of turbulent stresses.
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Mahamod, Yusuff. "Sedimentary processes in the Dwyryd Estuary." Thesis, Bangor University, 1989. https://research.bangor.ac.uk/portal/en/theses/sedimentary-processes-in-the-dwyryd-estuary(ca0aea23-480c-4032-ba10-12a9adee740c).html.
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This study aims to describe and quantify the important sedimentary processes which control the dispersal and accumulation of sediment in the Dwyryd Estuary, adjacent to Tremadog Bay in West Wales. It is shown that sedimentation in the estuary is dominantly control by fast tidal currents, and in the bay by weak tidal currents. Landward transport of coastal sediments by tidal currents is the residual sediment transport path. The spatial distribution of textural parameters of the estuarine sediments is related to the strength of tidal currents as well as the morphology and bathymetry of the study area. The estuarine sediments, predominantly sand, are very similar in texture and mineralogy to the adjacent beach sediments but markedly different to the river sediments. However, the beach sediments are slightly coarser and more poorly sorted than the estuarine sediments. In contrast, sediment in the deeper parts of Tremadog Bay are finer than both the estuarine and beach sediments due to the presence of substantial admixture of mud. The grain size distributions of most of the sediments are neither lognormal nor log-hyperbolic reflecting the great variability of hydrodynamic conditions in the study area. Using previously published flume data, a new sediment transport rate formula in the form of a power law has been developed for computation of total sediment load from the bed mean grain size and flow parameters: Uc The exponent n varies from 2.7 (for 0.93 mm sand) to 4.18 (for 0.19 mm sand). This is in contrast to the Bagnold (1966) formula which regards the exponent value (equal to 3) as constant for all grain sizes. Sediment transport patterns depend on the asymmetry between flood and ebb tidal currents due to distortion of the tidal wave on entering the estuary. Estimates of sediment budgets from surveyed profiles suggest that large amounts of sand have been transported from coastal areas into the estuary, supporting the mineralogical evidence. The estimates are of the same order of magnitude as estimates using flow velocity data and the above sediment transport formula.
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Rodrigues, Ann Maria de Jesus. "Environmental status of a multiple use estuary, through the analysis of bethnic communities : the Sado estuary, Portugal." Thesis, University of Stirling, 1992. http://hdl.handle.net/1893/2597.
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Ihis work on the Sado outer estuary (western coast of Portugal) considers its bio-sedimentary characterization, and evaluates the prevailing hydrophysical and sedimentary environmental conditions. The quality status of the estuary is discussed. The thesis is based on the analysis of superficial sediments and benthic macrofauna collected from 133 sites, and on hydrodynamical data obtained from a mathematical model. The environmental variables considered were the superficial sediment temperature, granulometry and organic matter content, together with the water current velocities, flow and shear stress. The macrofaunal characterization and the analysis of the state of disturbance was based on a study of the composition, structure and spatial distribution of faunal assemblages and their relationship to the prevailing environmental conditions. The Sado was shown to be inhabited by an abundant and diversified fauna with high biomass. Two major faunal assemblages have been identified, a marine and an estuarine community, separated by a transition region. The estuarine community comprises the majority of the area and contains important subdivisions. The regions identified have been shown either to be controlled by anthropogenic inputs or to reflect mainly the effects of natural forces. The main structuring factors influencing the benthos are the hydrodynamic conditions, coupled with sediment type, and organic matter of natural and anthropogenic origin. Sedimentary organic enrichment effects have been noted in all the areas studied and in general the Sado outer estuary reveals signs of eutrophic conditions. In the more disturbed regions the macrofauna data also suggest chronic toxicity effects. Although disturbance effects due to anthropogenic inputs are suggested through the biosedimentary approach, the estuary as a whole can not be considered badly polluted. However, defaunated, impoverished and over-enriched areas, appear as a result of localised severe pollution indicating the need to improve effluent treatment systems. The methodological approach followed in this study has been shown to be effective in assessing the quality status of the Sado outer estuary. Multivariate and direct gradient analysis proved to be very useful methods and a detailed analysis of the macrofaunal species has been shown to be effective in the detection of organic enrichment effects in some of the areas. The extreme aspects of the gradients were identified by all the analytical techniques, but the univariate methods were shown to be poor at discriminating the more subtle effects.
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Boonphakdee, Thanomsak. "Sources of organic matter and its transportation processes in a tropical river-estuary : the Bangpakong estuary, Thailand." Kyoto University, 2007. http://hdl.handle.net/2433/136568.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第13401号
農博第1656号
新制||農||948(附属図書館)
学位論文||H19||N4297(農学部図書室)
UT51-2007-Q802
京都大学大学院農学研究科応用生物科学専攻
(主査)教授 藤原 建紀, 教授 山下 洋, 教授 縄田 栄治
学位規則第4条第1項該当
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Chick, Christopher Roberts. "Benthic oxygen production in the choptank estuary." College Park, Md. : University of Maryland, 2009. http://hdl.handle.net/1903/10017.
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Thesis (M.S.) -- University of Maryland, College Park, 2009.Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Jianping, Lin. "Iodine speciation in the Yarra River estuary /." Connect to thesis, 1992. http://eprints.unimelb.edu.au/archive/00000216.
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Wojda, Mark. "Bank Erosion in the Petitcodiac River Estuary." Thesis, Fredericton: University of New Brunswick, 2011. http://hdl.handle.net/1882/35384.
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To further understand bank undercutting processes that occur in the Petitcodiac River estuary (New Brunswick, Canada), the erosion of sediment cores obtained at the base of the estuary banks was studied by testing for the critical shear stress and erosion rates in a laboratory flume.
It was found that there is variation in the erodibility of the sediment with depth horizontally into the bank over the depths tested. The bank cores were shown to erode in distinct layers, with the erosion of extremely weak layers occurring at rates that were an order of magnitude higher than the rates of adjacent resistant layers. Bed cores obtained at the toe of the bank were also tested and similar variability in sediment erodibility was found with vertical depth into the bed. Sediment properties of the cores, including particle size distribution, bulk density, water content, and organic content were compared to the erodibility of the sediment.
Additional investigations included observations of the Petitcodiac River estuary bank movement through GPS surveys and erosion pin monitoring, as well as testing for the presence of biological sediment-stabilization factors, and changes in particle size and mineralogy on the river bank.
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Maier, Gerald. "Nutrients and eutrophication in the Taw estuary." Thesis, University of Plymouth, 2009. http://hdl.handle.net/10026.1/2369.
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Increased inputs of nutrients to estuaries and coastal waters can cause undesirable effects associated with eutrophication, including nuisance and toxic algal blooms, reduced amenity value, changes in species composition, bottom anoxia and fish kills. The main sources of nutrients to estuaries are river runoff, sewage discharges, atmospheric inputs and possibly submarine groundwater discharges. For the UK, estuarine eutrophication has been shown to occur in at least 16 estuaries (including the Taw in North Devon). Consequently, these systems have been designated as '(Potential) Problem Area' under the OSPAR Common Procedure for the Identification of Eutrophication and also as a 'Eutrophic Water' under the EU's Nitrates Directive and I or a 'Sensitive Area (Eutrophic)' under the Urban Wastewater Treatment Directive or both. Significant reductions in N and P inputs have been realized following application of the EU's Urban Waste Water Treatment Directive. Atmospheric NOx and NHx emissions have also decreased and are expected to decrease further as implementation of existing legislation continues and new controls are introduced for activities such as shipping. The Nitrates Directive was introduced to tackle N discharges from agriculture but little change in N loads to estuaries has been recorded. Using the Taw Estuary as an example, data routinely collected by the Environment Agency for England and Wales (EA) over the period 1990-2004 were interrogated to identify the drivers of excessive algal growth. The estuary was highly productive with chlorophyll a concentrations regularly exceeding 100 µg Lˉ¹ , mostly during periods of low freshwater input from the River Taw when estuarine water residence times were longest. The reported approach demonstrates the value of applying conventional statistical analyses in a structured way to existing monitoring data and is recommended as a useful tool for the rapid assessment of estuarine eutrophication. However, understanding of primary production dynamics in the Taw was constrained because of the low temporal resolution, heterogeneity and gaps in the EA data. Therefore, a temporal high resolution monitoring campaign was conducted in summer 2008 to document the development and decline of three algal blooms. The significance of long water residence times following low freshwater inflow and neap tides was confirmed. During peaks in chlorophyll a concentration (max. 226 µg Lˉ¹ ) , nutrient limitation switched from P to Si and persisted for more than 2 weeks in the outer estuary. Signs of ammonium and phosphate ( <0.2 µM) and silicate ( <2 µM) depletion were also observed. Using multivariate statistics, five distinct sets of environmental conditions present in the Taw at different stages of algal growth were identified and directly linked to freshwater inflow. UK Climate Impacts Programme scenarios predict a 30-50% decrease in Q95 flows (the flow which is exceeded 95% of the time) of rivers in south Britain by 2050. Under the current nutrient regime, this is likely to severely increase the severity and duration of symptoms of eutrophication in the Taw and favour potentially hazardous phytoplankton groups instead of diatoms. To mitigate future eutrophication events in the Taw, it is recommended to further reduce N and P inputs. It is also crucial to perform a detailed assessment of potential climate change consequences for the Taw Estuary and similar systems.
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Herman, W. M. "Wave dynamics in a macro-tidal estuary." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603976.
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This study explores field and numerically modelled datasets on wave and wave-driven processes within the macro-tidal Blackwater Estuary in Essex, U.K. The wave climate of the Blackwater Estuary was characterised from wave records collected from 1994 to 1996 at 5 monitoring stations within the estuary. From these records and hindcasted offshore wave records over this period, locally-generated wind waves, wind-sea, and swell waves were identified and their significance assessed in terms of probability of occurrence and variability in different sections of the estuary. The Blackwater Estuary is found to be subject to waves from both offshore and from within the estuary, with evidence of seasonality within these wave climates. Longer-term wave and tidal height distributions were predicted through a Weibull probability model and their joint probability established for different return intervals. A numerical wave model (MWAVE_REG) was used to quantify the temporal and spatial impact of a variety of hydrodynamic scenarios (including 'worst case') within the Blackwater Estuary. The effects of wave diffraction, reflection and refraction were evaluated and areas of wave focusing within the estuary identified. The model was subsequently used to predict morphological changes per 1km shoreline, linking modelled hydrodynamics to observed morphological changes. The significance of the distribution of wave energy within the estuary for sediment entrainment, transport and deposition is discussed. In order to modify the highly artificial estuarine system of the Blackwater, a number of potential managed realignment sites were identified. From the hydrodynamic and morphodynamic findings of this study; these may aid in the reaction of a more natural estuarine system, better able to absorb extreme water local events.
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Hoban, T. J. "Polycyclic aromatic hydrocarbons in the Severn Estuary." Thesis, University of South Wales, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305737.
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Caeiro, Sandra Sofia Ferreira da Silva. "Environmental data management in the Sado Estuary." Doctoral thesis, FCT - UNL, 2004. http://hdl.handle.net/10362/1117.
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Estuaries are perhaps the most threatened environments in the coastal fringe; the coincidence of high natural value and attractiveness for human use has led to conflicts between conservation and development. These conflicts occur in the Sado Estuary since its location is near the industrialised zone of Peninsula of Setúbal and at the same time, a great part of the Estuary is classified as a Natural Reserve due to its high biodiversity. These facts led us to the need of implementing a model of environmental management and quality assessment, based on methodologies that enable the assessment of the Sado Estuary quality and evaluation of the human pressures in the estuary. These methodologies are based on indicators that can better depict the state of the environment and not necessarily all that could be measured or analysed. Sediments have always been considered as an important temporary source of some compounds or a sink for other type of materials or an interface where a great diversity of biogeochemical transformations occur. For all this they are of great importance in the formulation of coastal management system. Many authors have been using sediments to monitor aquatic contamination, showing great advantages when compared to the sampling of the traditional water column. The main objective of this thesis was to develop an estuary environmental management framework applied to Sado Estuary using the DPSIR Model (EMMSado), including data collection, data processing and data analysis. The support infrastructure of EMMSado were a set of spatially contiguous and homogeneous regions of sediment structure (management units). The environmental quality of the estuary was assessed through the sediment quality assessment and integrated in a preliminary stage with the human pressure for development. Besides the earlier explained advantages, studying the quality of the estuary mainly based on the indicators and indexes of the sediment compartment also turns this methodology easier, faster and human and financial resource saving. These are essential factors to an efficient environmental management of coastal areas. Data management, visualization, processing and analysis was obtained through the combined use of indicators and indices, sampling optimization techniques, Geographical Information Systems, remote sensing, statistics for spatial data, Global Positioning Systems and best expert judgments. As a global conclusion, from the nineteen management units delineated and analyzed three showed no ecological risk (18.5 % of the study area). The areas of more concern (5.6 % of the study area) are located in the North Channel and are under strong human pressure mainly due to industrial activities. These areas have also low hydrodynamics and are, thus associated with high levels of deposition. In particular the areas near Lisnave and Eurominas industries can also accumulate the contamination coming from Águas de Moura Channel, since particles coming from that channel can settle down in that area due to residual flow. In these areas the contaminants of concern, from those analyzed, are the heavy metals and metalloids (Cd, Cu, Zn and As exceeded the PEL guidelines) and the pesticides BHC isomers, heptachlor, isodrin, DDT and metabolits, endosulfan and endrin. In the remain management units (76 % of the study area) there is a moderate impact potential of occurrence of adverse ecological effects and in some of these areas no stress agents could be identified. This emphasizes the need for further research, since unmeasured chemicals may be causing or contributing to these adverse effects. Special attention must be taken to the units with moderate impact potential of occurrence of adverse ecological effects, located inside the natural reserve. Non-point source pollution coming from agriculture and aquaculture activities also seem to contribute with important pollution load into the estuary entering from Águas de Moura Channel. This pressure is expressed in a moderate impact potential for ecological risk existent in the areas near the entrance of this Channel. Pressures may also came from Alcácer Channel although they were not quantified in this study. The management framework presented here, including all the methodological tools may be applied and tested in other estuarine ecosystems, which will also allow a comparison between estuarine ecosystems in other parts of the globe.
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Hodder, Janet. "Production biology of an estuarine population of the green algae, Ulva spp. in Coos Bay, Oregon." Thesis, University of Oregon, 1986. http://hdl.handle.net/1794/9425.
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x, 106 leaves : ill., maps ; 29 cm
Notes Typescript
Thesis (Ph. D.)--University of Oregon, 1986
Includes vita and abstract
Bibliography: leaves 98-106
Another copy on microfilm is located in Archives
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Elston, Susan Anne. "Secondary Circulation in a Sinuous Coastal Plain Estuary." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-05042005-143327/.
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Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2005.Dr. Curry, Judith, Committee Co-Chair ; Dr. Blanton, Jackson - Committee Chair, Committee Chair ; Dr. Cunnold, Derek, Committee Member ; Dr. Seim, Harvey, Committee Member ; Dr. Webster, Donald, Committee Member ; Dr. Webster, Peter, Committee Member ; Dr. Wong, Kuo, Committee Member.
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Deyzel, (Shaun) Herklaas Phillipus. "Mesozooplankton dynamics in a biogeographical transition zone estuary." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1007901.
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This thesis presents the first intensive community-level investigation of the mesozooplankton from a biogeographical transition zone estuary. The Mgazana Estuary is located along a rural, semi-undeveloped part of South Africa’s east coast, believed to represent a transition zone between the subtropical and warm-temperate biogeographical zones. The research represented in this thesis involves data collected over a five year period between 2002 and 2006, with additional data collection made in 2008. The study focussed on five areas of investigation, the first of which investigated the physico-chemical dynamics of the Mgazana Estuary. The Mgazana Estuary exhibited marked vertical, horizontal and regional structures in the hydrological environment. Prominent vertical and horizontal stratification characterised summer months. A substantial turbidity front was observed in the lower estuary during summer and winter. The upper estuary was marked by considerable variation in multiple variables but especially salinity. These structures appeared to have shifted in position over the horizontal plane, which was attributed to variation in freshwater flow. The second study focused on the spatial dynamics of mesozooplankton in the Mgazana Estuary. The zooplankton was rich and in terms of composition typical of mangrove systems. The Copepoda were dominant, numerically and in terms of taxonomic representation. Calanoids Acartiella natalensis and Pseudodiaptomus hessei characterised middle and upper reaches in summer and mostly upper reaches in winter. On community level, a highly structured assemblage arrangement was observed during summer and winter months. These trends were further scrutinised under the theoretical framework of ecological boundaries. In so doing, an agreeable spatial association emerged between specific assemblages and their environments. These trends were concluded to reflect ecoclinal as well as ecotonal properties, the latter describing interactions over narrow spatial bands of marked changes in turbidity. The third study investigated flooding events as short-lived extreme meteorological events and the influence on zooplankton. Within this regard, second-stage multivariate statistics was used to assess year-to-year variability in assemblage structures on whole-system and regional scales. The impact of two major flooding events that flushed the estuary some days prior to sampling could clearly be elucidated. Flooding emerged as a significant source of inter-annual variability in the zooplankton of the Mgazana Estuary. Second-stage multivariate analysis proved to be an effective analytical strategy for investigating inter-annual variability in species assemblage structures. Results from the preceding study prompted a detailed investigation into the spatio-temporal dynamics of Acartiella natalensis, the most important zooplankton species of the system aimed at elucidating flood responses. Acartiella natalensis showed indication of temporal arrest in association with flooding events in a similar fashion as is observed in seasonal variation trends in estuaries towards its geographical distribution limit south of the study area. It was concluded that A. natalensis was severely affected by floods and the possibility exist for entrainment of entire populations from the estuary during flooding events. The final study tested the hypothesis of post-flood propagation from a resting egg bank in the sediments of the Mgazana Estuary. Preliminary data revealed that numerous eggs were present in the sediments. Nauplii hatched from eggs under laboratory conditions were identified as belonging to the family Acartiidae. The preliminary mode of diapause is presented as a schematic model, emphasising the role of freshwater flow and specific environmental variables. This was the first discovery of resting eggs from a subtropical estuary from South Africa. It is hoped that the findings of this study would give rise to new research initiatives investigating the importance of resting stages in estuarine and coastal Copepoda species and the role such reproductive strategies may play in estuarine functioning.
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Bourgault, Daniel. "Circulation and mixing in the St. Lawrence estuary." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37871.
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Circulation and mixing processes in the St. Lawrence Estuary are examined using both newly acquired and historical observations, as well as numerical modeling. In the Summer of 1997 a field experiment was undertaken to verify the prediction of a three-dimensional numerical model on the occurrences of shear instabilities within the upper estuary. The instabilities were found as predicted and documented from acoustic imaging, current profiler and density measurements. The instabilities, as in the case of Kelvin-Helmholtz instabilities, first develop in the form of wavelike disturbances before they break. The unstable waves have wavelength of around 140--150 m and a vertical extent of between 10 and 25 m. It is shown that the modeled gradient Richardson numbers near the pycnocline are reasonably well reproduced and appear to be useful for the prediction of flow instabilities in such a complex environment.The seasonal variability of the general circulation and mixing is examined with a newly developed laterally averaged numerical model. The model takes into account tidal forcing and a realistic topography while forced with a large seasonal change in the river discharge. The model is able to reproduce important processes associated with the tidal forcing and mean conditions (density field, residual circulation). The numerical results show that mixing in the St. Lawrence Estuary is not evenly distributed. Mixing is found to be large near the sill at the head of the Laurentian Channel, as previously thought, as well our new results show that equivalent levels of mixing are also found near English Bank and near Ile-aux-Coudres. During the spring freshet, when the river discharge is 40% higher than normal, the limit of salt intrusion is moved seaward by approximately 12 km, the residual circulation is intensified by approximately 10%, and the turbulent vertical mass flux increases throughout owing to greater availability of freshwater. The results also suggest that during high runoff periods, the vertical stability of the water column increases in the upper estuary.
The model is also used to assess the impacts of climate change on the estuarine dynamics. (Abstract shortened by UMI.)
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Gow, T. A. K. "Studies on benthic microalgae in a polluted estuary." Thesis, University of the West of Scotland, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354365.
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Nairn, H. J. "Fish fauna of the Avon-Heathcote Estuary, Christchurch." Thesis, University of Canterbury. Zoology, 1998. http://hdl.handle.net/10092/6872.
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Aspects of the biology of common fish species in the Avon-Heathcote Estuary were investigated from two distinct types of sample site, during two sample periods between July 1996 and April 1997. The sites consisted of sites 1-6 (channel sites), which were sampled using a seine net, and estuarine fringe sites A-F, which were dip-net sampled. Although a relatively low diversity of fish species were captured, this was believed to be partly due to sampling methods and conditions. The species that were captured however did appear to be healthy, and were feeding in the estuary. Gonad analyses indicated that most of the adult Rhombosolea leporina in the estuary were nearly ripe females, that may have been in the estuary to feed prior to spawning elsewhere. The estuarine fringe sites had an abundance of juvenile flatfish of both common species Rhombosolea Ieporina, and R. plebeia, which were using these areas as "nurseries" as they possessed food and cover from predators.
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Findlay, John Smith. "Geochemistry of suspended particles in the Tamar estuary." Thesis, University of Plymouth, 1990. http://hdl.handle.net/10026.1/514.
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Upstill-Goddard, R. C. "Geochemistry of the halogens in the Tamar estuary." Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354529.
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WANDERLEY, CRISTIANA VILLELA DE ARAUJO. "SEDIMENTATION RATES CHANGES AT PARAÍBA DO SUL ESTUARY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24946@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
A cidade de Atafona situada à foz do Rio Paraíba do Sul (RPS) vem sofrendo erosão em sua linha de costa por muitas décadas. Este estudo consiste em uma avaliação das taxas de sedimentação no estuário do Paraíba do Sul e suas correlações com a forte erosão que ocorre em Atafona, Rio de Janeiro. O trabalho foi baseado em quatro transetes ao longo do Estuário do rio Paraíba do Sul contendo 14 pontos de coleta. Cerca de 540 amostras de sedimentos foram obtidas em Janeiro de 2010 e Fevereiro de 2011. As taxas de sedimentação foram determinadas a partir do método da datação com 210Pb e os inventários de 210Pb foram determinados para todos os pontos de coleta. Foram aplicados dois modelos para a determinação das taxas de sedimentação: o modelo da Concentração Inicial Constante (modelo CIC) e o modelo da Razão de Suprimento Constante (modelo CRS). Os resultados da datação 210Pb foram validados com base na variação da concentração elementar ao longo de dois testemunhos. A determinação de elementos foi realizada utilizando a técnica de Espectrometria de Massa com Plasma Indutivamente Acoplado (ICP-MS). A análise multivariada de dados foi aplicada através da análise de fatores principais (AFP) e análise hierárquica de cluster (AHC) a fim de obter informações que traduzam quantitativamente a composição dos sedimentos descrevendo a região. Os inventários de 210Pb determinados nos pontos de coleta, localizados ao sul do rio Paraíba do Sul (RPS), foram maiores do que os determinados nos pontos de coleta localizados ao centro e ao norte da saída do rio. O valor médio do inventário obtido nos pontos de coleta ao sul da foz do RPS foi de 1,0 Bq cm-2, muito superior ao valor médio obtido nos pontos situados ao norte da foz do rio, com valor de 0,16 Bq cm-2, indicando que os sedimentos são transportados na direção sul da foz do RPS, ao longo da costa com as correntes de deriva existentes nesta direção. A taxa de acumulação estimada para as camadas mais profundas foi de 0,06 g cm-2 ano-1. Essa taxa representa um valor base para a taxa de acumulação de sedimentos para o período anterior a 1950. As taxas de acumulação obtidas para o período mais recente variaram de 0,2 g cm-2 ano-1 nos pontos situados ao norte e ao centro a 0,6 g cm-2 ano-1 nos pontos situados ao sul da foz do RPS. Observou-se que as concentrações de Cr, Cu, Cd e Zn aumentaram significativamente a partir dos anos oitenta que, coincide com a época do acidente ocorrido com a Cia. de Paraibuna Metais em 1982. Uma das consequências nas mudanças no uso da terra e do represamento de rios é a mudança na natureza dos sedimentos que chegam e se depositam no delta do RPS. A normalização da concentração dos metais pelo alumínio pode ajudar a traçar tais mudanças, principalmente com elementos de origem distinta, como Ca e Mg. Através da curva obtida entre razão a Mg/Al e as idades das camadas sedimentares pode-se observar uma forte mudança no período entre 1962 e 1988. Foram identificados quatro fatores através da AFP traduzindo quatro fases do sedimento: duas representando a matriz, uma representando os carbonatos e a outra representando os sulfetos.
The city of Atafona, situated at Paraíba do Sul Estuary, has been suffering erosion in its coastline for decades. This study is an evaluation of sedimentation rates in the Paraíba do Sul estuary and its correlation with the strong erosion that occurs in Atafona city, Rio de Janeiro, Brazil. We performed four transects along Paraíba do Sul Estuary with 14 sampling points. About 540 sediment samples were collected in January 2010 and February 2011. Sedimentation rates were determined by 210Pb dating method and inventories of 210Pb were determined for all sampling points. Two models were applied for the sedimentation rates determination: the Constant Initial Concentration model (CIC-model) and the Constant Rate of Supply model (CRS-model). The 210Pb dating results were validated based on the elemental concentration variation throughout two of the sediment cores. The elements determination was performed using the mass spectrometry with inductively coupled plasma technique (ICP-MS). The multivariate analysis were applied trough the principal factor analysis (PFA) and hierarchical cluster analysis (HAC) in order to obtain factors that may traduce quantitatively the sample composition describing the region. At sampling points located at south of the Paraiba do Sul River (PSR) mouth, 210Pb inventories were higher than those at the northern and central sampling locations. The inventory average obtained at south was 1.0 Bq cm-2, much higher than those located at north of the river mouth, with a mean value 0.16 Bq cm-2, indicating that the sediments are transported southward by the alongshore current. The accumulation rate estimated for the deeper layers was 0.06 g cm-2 yr-1, which represents a reference value of sediment accumulation rate for the period prior to 1950. Accumulation rates obtained for the most recent period ranged from 0.2 g cm-2 yr-1 in the points situated at north and center to 0.6 g cm-2 yr-1 in points located at south of RPS mouth. It was observed that Cr, Cu, Cd and Zn concentrations increased significantly from the eighties that matches with the Cia Paraibuna Metals accident occurred in 1982. A consequence of changes in land use and the damming of the river is a change in the nature of the particulates reaching the PSR delta. The normalization of elemental concentrations to aluminum could help trace these changes, particularly for elements with a distinct origin, such as Ca and Mg. The Mg/Al versus ages plot showed a strong change between 1962 and 1988. There were four factors identified that traduce four sediment phases, two of them were related to the matrix, other was related to the carbonate phase and the other representing sulfides phase.
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Woodruff, Jonathan Dalrymple. "Sediment deposition in the lower Hudson River estuary." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80032.
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Thesis (S.M. in Civil and Environmental Engineering)--Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering; and the Woods Hole Oceanographic Institution), 1999.Includes bibliographical references (leaves 54-57).
by Jonathan Dalrymple Woodruff.
S.M.in Civil and Environmental Engineering
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Hegermiller, Christie A. "Fine Sediment Trapping in the Penobscot River Estuary." Thesis, Boston College, 2011. http://hdl.handle.net/2345/2000.
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Thesis advisor: Gail KinekeThe Penobscot River Estuary is heavily contaminated with mercury; previous studies indicate maximum mercury concentrations of 4.6 ppm within the Frankfort Flats reach. The transport and trapping of this contaminant is linked to the transport and trapping of fine sediment within the estuary. Hydrographic and flow measurements, coupled with a spatial and temporal characterization of the bottom sediments, were performed during and following the freshet in 2010 to determine the mechanisms driving sediment transport and trapping within the estuary. The Penobscot River likely has a turbidity maximum associated with the landward extent of the salinity intrusion that is positioned over the Frankfort Flats reach during average discharge and tidal conditions. This turbidity maximum may be responsible for a patch of fine sediments in the Frankfort Flats reach in an otherwise coarse-grained bed. Additional transport and trapping of fine sediments within this reach is the result of secondary circulation driven by centripetal acceleration around meanders in the channel. Close proximity of meanders at Frankfort Flats, within ~5 km, creates opposite secondary circulation of magnitude ~0.2 m/s during flood and ebb conditions
Thesis (BS) — Boston College, 2011
Submitted to: Boston College. College of Arts and Sciences
Discipline: Geology & Geophysics Honors Program
Discipline: Earth and Environmental Sciences
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Amini, Sina. "Hydrodynamics and Salinity of Pontchartrain Estuary During Hurricanes." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1845.
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A hurricane is a combination of sustained winds, low atmospheric pressures and precipitation. Over the past decades, Louisiana has experienced several devastating hurricanes.
The east bank of the City of New Orleans is bounded by Lake Pontchartrain to the North and the Mississippi River to the South. Lake Pontchartrain is a brackish system connected to the Gulf of Mexico through Lake Borgne to the East. As a Hurricane enters the Estuary from the Gulf of Mexico, it imposes a sustained surge of a few meters which may lead to flooding in areas which are not protected by levees. These flood water may be saline.
Saltwater flooding is an environmental issue in flooded marshlands since saltwater can be fatal to some plants. The response of salinity and storm surge to hurricane duration which represents the forward speed of the storm is numerically modeled.
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Watts, Sarah Jane. "Recovery of the Mersey Estuary from metal contamination." Thesis, University of Plymouth, 2004. http://hdl.handle.net/10026.1/2133.
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The Mersey Estuary has received significant quantities of industrial wastes and sewage over several decades. Although contarninant loads are reducing and the estuary is showing signs of recovery, the sediment reservoir remains a repository of historical contamination and still contains high concentrations of trace metals and organic compounds. A combination of hydrodynamic, sedimentary and geochernical processes are responsible for maintaining trace metal concentrations at present-day levels. The distributions of trace metals in bed sediments reflect changes in granulometry, differences in POC content and the magnitude of past inputs rather than the locations of point sources in the estuary. The association of contaminant metals with SPM varies not only with axial changes in salinity and particle concentration but also in response to the relative magnitudes of freshwater and tidal inflows and cyclic variations in water and particulate chemistry that occur on intratidal, intertidal and seasonal timescales. The most influential of these arise from axial changes in dissolved oxygen and the delivery. of organic carbon from both external and internal sources which modify the relative degree of sorptive control exerted by Fe, Mn and organic C at different locations in the estuary and at different times. These factors, combined with the efficient trapping of sediments and possible salting out of neutral metalorganic complexes, assist in the retention and internal recycling of particles and associated metals betweent he bed and water column. Geochernicalr eactivity is suppressedin Mersey SPM and metal decontamination is not predicted to occur through the loss of particulate metals to the surrounding coastal zone. Rather, it is envisaged that sediment resuspension and the desorption of metals into fresh and low salinity waters, supplemented by the release of metals from tidally stirred diagenetically modified sediments, are more likely to be important long term cleansing mechanisms, with the latter occurring particularly during the summer months when bacterial numbers and the degradation of accumulated organic detritus becomes more pronounced. Futured eclinesi n metalsf rom bed sedimentsh aveb eene stimatedu sing two methodsa nd two independendt ata sets. Resultingv aluesa re not only metal-dependenbtu t also vary with sedimentlo cation.L osseso f Cd, Co, Cu, Hg, Ni andZ n arep redictedt o takeu p to 40 years,w hilst removal of substantiallye levatedc oncentrations of Pb in sedimentsin the upper estuary could span hundreds of years.
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Abdulkade, Akirat. "The dynamics of Cobble Dunes, Severn Estuary UK." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/415839/.
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Dunes are one bedform type which can be found underwater and which have an impact on flow resistance and play an important role in engineering structure design, navigation as well as dredging strategies. Existing literature focuses on the formation and processes associated with dunes developed by sandy sediment and has paid little attention to those developed in coarse sediment, i.e. cobble dunes. This research will focus on the dynamics of a set of coarse cobble dunes located on Hills Flats, in the Severn Estuary, UK. The features are composed of a range of sediment sizes; from small boulders, coarse cobbles, pebbles, to finer components. The dunes are exposed during low water period, especially during Spring tides, when direct measurements of the dunes could occur. Specifically, data related to dunes dynamics were collected by a number of techniques including measuring the dune shape by using dGPS, recording near-bed flow velocity data with current meter, sampling bedload transportation to imply the movements of pebbles or cobbles, and measuring the basic morphology of dunes located on the site and to obtain first interpretations of dune dynamics. Data from these techniques were processed to demonstrate the roughness effects on tidal flows and the subsequent influence on the bulk flow field. The results of this study show that the dunes, D 50~ 16.7 mm, move only on the highest Spring tides and reverse direction of migration with each flood and ebb tide while little movement on Neap tides is recorded. The migration is low with the maximum rate only 1.1 cm per tide. The dune scale varies but usually less than 1 m high and 4 – 10m long. Water depth, flow velocity and bed shear stress over the dunes could exceed 10 m, 2 m/s and 80 N/m2 respectively. The initial motion of pebbles could start in a range of 0.3 – 50 N/m2. The dynamics of the bedforms are explained by the tidal asymmetry which mediates the temporal distribution of bed shear stress, understanding of which provide benefits to several aspects such as engineering of structures and environmental management planning in this area and other similar locations.
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Viskich, Michal. "Long-term changes in a small, urban estuary." Bachelor's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/12825.
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Includes bibliographical references.The Diep River estuary is a small, urban estuary situated in the suburbs of Cape Town and has been subjected to long-term modifications and abuse that far exceeds that of most other estuaries around South Africa. Activities in the Diep River catchment, together with the intensive urban development in the areas adjacent to the estuary, have resulted in massive changes in biodiversity, altered flow and salinity regimes; causing a marked deterioration in water quality and a frightening increase in non-indigenous species introductions. Several studies have been undertaken at the Diep River estuary, however, they are out-dated and many changes have occurred within the last few decades. The aim of this study was to provide an up-to-date list of the fauna residing within the Diep River estuary, as well as to provide a synthesis of all the major physical, hydrological and faunistic changes that have occurred within and around the estuary, dating back to the late 1800s, whereas faunistic changes are described using information provided by several earlier surveys dating back to the early 1950s. Infauna, epifauna and salinity were taken at designated stations along Milnerton Lagoon. Prawn (Callichirus kraussi) counts were also made in order to determine current abundance and distribution. Results showed a substantial decline in sand prawn abundance with the estimated standing stock calculated at just over 12 million. Fauna collected were generally poor in abundance and were mainly limited to euryhaline, detritus feeders. Earlier surveys conducted in the 1950s recorded at least 49 infauna and epifauna species residing within Milnerton Lagoon, whereas in 1974, only 23 species were found. Similarly, 24 species were recorded in this study. The European shore hopper (Orchestiagammarella) was recorded as a new introduction within the system. Only five fish species were recorded in the summer period, including the highly invasive mosquito fish (Gambusiaaffinis), which was found in relatively high abundance within the lagoon. A regular monitoring of the infauna and epifauna populations for this system needs to be established, in order to obtain a clear picture of the faunistic distribution and changes occurring within this highly dynamic environment. Additionally, serious management protocols need to be established in order to prevent the further degradation of this important system.
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Rosa, Mónica Sofia Soares. "Hydrodynamical and biogeochemical modeling study of Sado estuary." Master's thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/7392.
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Mestrado em Ciências do Mar e Zonas CosteirasThe Sado estuary is located in the surrounding area of an important Portuguese natural park (Arrábida Natural Park) near the city of Setúbal. The low freshwater discharge from Sado River, the mesotidal tide along the estuary and the strong currents observed turn the estuary a well‐mixed system, controlling the estuarine residence time, and therefore determining the patterns of conservative and nonconservative tracers. The salt dynamics inside this kind of system is very important, since salinity may be considered a natural tracer, allowing the comprehension of the dynamics of other conservative tracers. In such a system is also important to analyze the water quality determining the coliforms propagation from selected discharge stations and analyzing its relation with the estuarine hydrographic features. In this study, a two‐dimensional hydrodynamic model is implemented for the Sado estuary in order to study the horizontal patterns of salinity, as well as the propagation of fecal coliforms from sewage stations, both under different tidal and freshwater forcing conditions. The model used in this study is Mohid‐2D (www.mohid.com), a marine model that uses the shallow water approximation to study vertically homogeneous systems like the Sado estuary. The model domain includes the whole area of the estuary, using a realistic coastline and bottom topography The model results are explored in order to evaluate salinity differences between flood and ebb, spring and neap tide, and low (2m3s‐1), medium (50m3s‐1) and high (200m3s‐1) river inflow. Moreover, the propagation of fecal coliforms from sewage stations is also studied in light of different tidal and freshwater inflow conditions. Sea surface height and velocity model outputs are compared to in‐situ data, revealing the model skill in reproducing the tidal propagation along the Sado estuary. When the river inflow is weak (2m³/s), the hydrography of the estuary is clearly tidal dominated but when the river inflow is high (200m³/s), the horizontal patterns of salinity inside the estuary are determined by a balance between tide and river inflow effects. In this case is found a classic division of the estuary in three distinct regions: marine, mixing and freshwater. In this last region the estuary dynamics is mainly modulated by the freshwater discharge. Despite the significant estuarine dynamics, the concentration of fecal coliforms was found confined to small areas close to the discharge points. These organisms were found to affect only a restricted area near the sewage stations, with low concentrations found far the discharge points along the estuary.
O estuário do Sado encontra‐se inserido no parque natural da Arrábida junto à cidade de Setúbal. A baixa descarga de água doce proveniente do rio Sado, a maré mesotidal ao longo do estuário e as fortes correntes que aqui se observam tornam o estuário um sistema bem misturado, controlando o tempo de residência e determinando assim os padrões de traçadores conservativos e não conservativos. A dinâmica salina no interior deste tipo de sistemas é muito importante, uma vez que a salinidade pode ser considerada um traçador natural, permitindo a compreensão da dinâmica de outros traçadores. Num sistema como este, é também importante analisar a qualidade da água, determinando a propagação de coliformes provenientes de estações de descargas seleccionadas e analisando a sua relação com as estruturas hidrográficas do estuário. Neste estudo, um modelo hidrodinâmico bidimensional é implementado para o estuário do Sado, com o objectivo de estudar os padrões horizontais de salinidade, bem como a propagação de coliformes fecais com origem em estações de esgoto locais. São avaliadas condições distintas de maré (maré‐viva, maré‐morta), diferentes fases da mesma (enchente e vazante) e descargas características do caudal fluvial (baixo (2m3s‐1), médio (50m3s‐1) e elevado (200m3s‐1)). O modelo usado neste estudo foi o MOHID‐2D (www.mohid.com), um modelo marinho que utiliza a aproximação de águas pouco profundas para estudar sistemas verticalmente homogéneos, como é o caso do estuário do Sado. O domínio do modelo abrange toda a área do estuário, usando a linha de costa e topografia de fundo realista. Os resultados do modelo são explorados de modo a avaliar as diferenças de salinidade entre enchente e vazante, maré‐viva e maré‐morta e baixo, médio e elevado caudal fluvial. Posteriormente foi ainda estudada a propagação de coliformes fecais nas condições anteriormente referidas. As previsões do modelo em termos de velocidade e nível de maré são comparadas com observações in situ, revelando a capacidade do modelo em reproduzir adequadamente a propagação de maré ao longo do estuário do Sado. Quando o caudal fluvial é fraco (2m3s‐1), a hidrografia do estuário é claramente dominada pela maré, quando este é elevado (200m3s‐1) os parâmetros horizontais de salinidade dentro do estuário são determinados por um balanço entre o efeito da maré e do caudal fluvial. Neste caso é perceptível a divisão do estuário em três regiões: marinha, de mistura e de água doce. Nesta última a dinâmica do estuário é principalmente modulada pela descarga de água doce proveniente do rio. Apesar da dinâmica estuarina, as concentrações de coliformes fecais mostraram estar confinadas a pequenas áreas junto às estações de descarga de esgoto, sendo detectadas concentrações bastante baixas em zonas mais afastadas dos pontos de descarga e ao longo do estuário.
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Arnott, Kimberly. "Friction-dominated water exchange in a Florida estuary." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041345.
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Pearson, Holly Beverley Clare. "Copper and zinc speciation in the Tamar Estuary." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/9584.
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The chemical speciation of trace metals controls their potential bioavailability and therefore toxicity to exposed organisms. Despite previous studies demonstrating the ameliorative effects of dissolved organic carbon (DOC) on metal toxicity, the effectiveness of ligands from varying sources and of potentially variable composition in controlling speciation has not been studied in detail in estuarine waters. In addition, the effect of DOC on radionuclide contaminants in combination with trace metals has not been investigated in any waters. This is of particular interest in the estuarine environment, where both anthropogenic and natural ligands, and contaminants that pose a potential threat to ecosystem health, can be present. Competitive ligand exchange adsorptive cathodic stripping voltammetry (CLE-AdCSV) with complexation capacity titrations was employed to determine the speciation of dissolved Cu and Zn, two metals that possess revised environmental quality standards (EQS) which now account for potential metal bioavailability. Dissolved metal concentrations in the < 0.4 and < 0.2 μm filter fractions of samples from the Tamar Estuary were determined during seasonal transects made over a calendar year. Samples were taken over a full salinity range (0-35) and from locations thought to contain DOC from a variety of sources (e.g. terrigenous, biogenic, sewage). No seasonal trends in metal speciation were identified, but a semi-quantitative assessment of DOC type using 3-D fluorimetry showed domination of humic and fulvic type ligands in the upper estuary, and biogenic-type ligands in the lower estuary, the former appearing the most important in controlling Cu and Zn complexation. Filter size fraction differences showed a major portion of the dissolved metal is associated with the 0.2 ≥ 0.4 μm fraction, indicating an importance of larger molecule ligands in controlling potentially bioavailable metal. Sample ligand concentrations ([L_x]) ranged from 1-372 nM (Cu) and 3-412 nM (Zn), and metal-ligand conditional stability constants (log K_(ML_x )) from 10.5-13.5 (Cu) and 7.5-10 (Zn), which are similar to reported literature. Calculated free metal ion concentrations ([M2+]) of 0.3 – 109 nM (Zn) and 1.4 x 10-13 – 7.3 x 10-11 M (Cu) compared well (92% showed no significant differences (P = 0.02)) with direct measurements of [Zn2+] made for the first time in estuarine waters using “Absence of Gradients and Nernst Equilibrium Stripping” (AGNES) after optimisation for estuarine waters. AGNES fully complements CLE-AdCSV in terms of analytical capability and shows that methods are now available that are capable of directly determining [Zn2+] in estuarine waters for use in environmental monitoring studies. Calculations made using the chemical equilibrium speciation programme Visual MINTEQ (VM) showed [Cu2+] and [Zn2+] could be predicted to within one order of magnitude of measured values when log K_(ML_x ) and [L_x] are determined and input into the model. This was in contrast to poor agreement between measured and predicted [M2+] when VM was used with the NICA-Donnan complexing model, which assumes a set portion of the total DOC concentration input is fulvic acid that actively complexes metals. These results corroborate a lack of identification of a relationship between metal speciation in the Tamar samples and DOC concentration, highlighting that knowledge of DOC type, log K_(ML_x )and L_x are important when assessing environmental risk, setting EQSs and for accurate modeling of [Cu2+]. Finally, a combined chemical and biological study investigating the effects of mixtures of DOC, Zn and the radionuclide tritium (3H) on the marine mussel presents the first evidence of a protective effect of Zn on DNA damage caused by 3H. The association of 3H with DOC remains elusive and an assessment of DOC type is recommended for future research, but the study emphasises the importance of investigating mixture effects in order to avoid inaccurate risk assessment and potentially costly site remediation.
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Boyer, Joseph N. "Degradation and mineralization of chitin in an estuary." W&M ScholarWorks, 1987. https://scholarworks.wm.edu/etd/1539616579.
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A method for measuring microbial degradation and mineralization of radiolabeled native chitin is described. ('14)C-labeled chitin was synthesized in vivo by injecting shed blue crabs (Callinectes sapidus) with N-acetyl-D- ('14)C -glucosamine, allowing for its incorporation into the exoskeleton. The cuticle had a total organic content of 0.48 mg C mg('-1) with a specific radioactivity of 6762 DPM mg('-1). Glucosamine i.e. chitin content, as determined colorimetrically, was 22% (w/w). Rates of chitin degradation and mineralization in estuarine water and sediments were determined as functions of temperature, inoculum source, and oxygen condition. Significant differences in rates between temperature treatments were evident. Q(,10) values ranged from 1.2 to 2.5 for water and sediment, respectively. Increased incubation temperature also resulted in decreased lag times before onset of chitinoclastic bacterial growth and chitin degradation. The highest rate, 284 mg day('-1)g('-1) seeded chitin, occurred in the water column inoculum at 25�C. The lowest rate, 83 mg day('-1) g('-1), was found in the anaerobic mud inoculum incubated at 15�C. Over 95% of particulate chitin degraded by water column bacteria was mineralized to CO(,2) with no apparent lag between processes. No measurable dissolved pool of radiolabel was present. Conversely, only 75-80% of chitin degraded by sediment inocula was mineralized. Label recoveries in the dissolved pool ranged from 6 to 17%. The anaerobic treatment possessed the highest pool of dissolved organic carbon due to the fermentation of chitin to volatile fatty acids. The anaerobic pathway of chitin decomposition by chitinoclastic bacteria was examined with an emphasis on end product coupling to other bacterial types. Actively growing chitinoclastic bacterial isolates produced primarily acetate, hydrogen, and carbon dioxide in broth culture. No sulfate reducing or methanogenic isolates grew on chitin as sole carbon source nor produced any measureable degradation products. Mixed cultures of chitin degraders and sulfate reducers resulted in positive sulfide production. Mixed cultures of chitin degrading isolates with methanogens resulted in the production of methane with concurrent reductions in headspace hydrogen and carbon dioxide. The combination of all three metabolic types resulted in the simultaneous production of methane and sulfide. More methane was produced in mixed cultures containing CO(,2)-reducing methanogens and acetoclastic sulfate reducers due to less interspecific hydrogen competition.
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Taylor, Arthur. "A trace element study of sediments from the Olifants River estuary, the Berg River estuary, and the off-shore Mud Belt." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/9027.
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Includes bibliographical references (leaves 99-105).Trace elements have received increased attention since the mid-1900's. Although some studies have investigated trace element accumulation as a result of urban expansion in the Western Cape, South Africa, few have catalogued the accumulation and behavior of trace elements resulting from agricultural practices. This study investigates the distribution and behavior of trace elements for the Olifants and Berg river catchments by focusing on the sediments of the estuaries. The dominant industry in both catchments is agriculture and there exists relatively little urban sprawl. Two sediment samples taken from the offshore mud belt in the vicinity of the two river mouths were also analyzed. The sediments were analyzed for trace elements using inductively coupled plasma mass spectrometry (ICP-MS), major elements using X-ray fluorescent spectroscopy (XRF), total sulfur using XRF, total and organic carbon using a C:H:N analyzer, and grain size analysis was performed (>62 μm, 38-63 μm, 2-38 μm, <2μm). The mud belt cores were dated using 14C dating. Estuarine surface waters were analyzed for trace elements, pH, dissolved oxygen (DO), electrical conductivity (EC), and temperature. The trace elements arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) were focused on. The trace element concentrations in the sediments were compared with those of soils that occur in the study area, as well as their parent materials, to determine background concentrations. The concentration profiles of elements with respect to depth are compared with natural deposition rates to recognize signs of recent enrichment of individual trace elements. Inter-element comparisons are made in an attempt to determine speciation. Comparison between the estuarine and mud belt sediments were made to assess the estuaries ability to filter fluvial trace elements, as well as to determine the sediment contributions of the Olifants and Berg rivers to the mud belt. Statistical analysis was performed to"group sediment populations Trace element and organic matter concentrations showed strong positive correlations with fine-sized particles. The mud belt sediments displayed considerably more OC than the estuarine sediments. The trace elements appear to associate predominantly with clay minerals (alumino-silicates), Fe/Mn oxides, and organic matter. Trace element correlations with S and carbonate carbon were also observed. Comparison with estimates of natural deposition rates and compositions of soils occurring in the catchments did not suggest an anthropogenic pollution input. From the data available the estuarine and Mud Belt sediments appear enriched in Cd, Cu and Zn in comparison to the background soils. The estuaries seem to effectively trap Zn and Pb, but do not capture As well. Statistical analysis suggest that, of the rock types considered, the sediments of the Olifants and Berg river estuaries and those of the off shore mud belt are most similar to sediments derived from the Malmesbury and Ecca Groups. The Olifants and Berg rivers are important sources of water for the farming community, as well as for municipal use in the Western Cape. Based on this investigation of the estuarine waters and sediments the rivers appear to be in good health in regards to trace element concentrations.
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Groenewald, Christoff J. "Macrobenthic community structure across an inter- and subtidal gradient in a mangrove estuary." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1240.
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Macrozoobenthic community structure and composition was investigated along a subtidal-intertidal gradient in the Mngazana Estuary. Six transects were sampled between the spring high water mark (HWST) and the bottom of the river channel in the lower estuary. Fifteen replicate samples were collected along each transect using a Van Veen type grab (211 cm2 bite) during each of three sampling sessions. Samples were sieved through a 500 μm mesh bag and the invertebrates stored in bottles for further analysis in the laboratory. Additional grab samples were collected for sediment particle size analysis and organic matter. Physical variables measured at each transect included: salinity, temperature, dissolved oxygen, depth, pH, percentage mud, organic content and turbidity. Sediment compactness was measured at all intertidal transects and additional sediment samples were collected at mid shore and high shore transects for percentage water content analysis. A total of 104 species were recorded along the intertidal-subtidal gradient in the sampling area. Species richness was higher in the subtidal zone compared to the intertidal zone and polychaetes numerically dominated the macrozoobenthic community at most transects, during all three sessions. At high shore transects the community was characterised by having fewer species, consisting mostly of brachyurans, polychaetes and gastropods. Shannon diversity index (H’) was generally higher for subtidal transects (x¯ = 2.3; range: 2.8 to 1) than for intertidal transects (x¯ = 1.4; range: 2.2 to 0.6) indicating that the distribution of individuals among species in the intertidal zone experienced greater variability. Results for Hill’s numbers followed the same trend as Shannon diversity with subtidal communities mostly consisting of abundant species followed by very abundant species. Intertidal communities generally exhibited lower numbers of abundant and very abundant species. Sedimentary characteristics played a major role in structuring benthic communities in comparison to other physico-chemical variables. Organic content and mud content of the substrate were identified as important factors influencing community patterns observed along the subtidal-intertidal gradient. In addition, sediment compactness and water content of the substrate was found to influence intertidal community structure. Subtidal community structure possibly had a greater dependence on seasonal variations in abiotic and/or biotic factors. Cluster dendrograms used in conjunction with MDS ordination mapping revealed that macrozoobenthic communities were generally distinct between high shore intertidal transects iii and subtidal transects. Most species exhibited a broad spatial distribution along the subtidal-intertidal gradient with mid and high shore transects being the exception. Most species also exhibited marked shifts in abundance and this was especially noticeable at the transition between the subtidal and intertidal zone. Two polychaete species, Prionospio sexoculata and Capitella capitata, were very abundant species and featured amongst the most numerically dominant species collected during each sampling session.
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Fernandes, Elisa Helena. "Modelling the hydrodynamics of the Patos Lagoon, Brazil." Thesis, University of Plymouth, 2001. http://hdl.handle.net/10026.1/679.
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The Patos Lagoon, the largest choked coastal lagoon in the world, is a typical centre of population, commerce, industry and recreation, and consequently it is also a site for disposal of industrial, agricultural and municipal wastes. Important questions concerning beneficial uses of and potential changes to the lagoon and its estuary are left unanswered without a good understanding of hydrodynamic processes. The current study involves the choice, calibration and application of a numerical model which can be used in future hydrodynamic, sediment transport and water quality studies in the area. The two- and three-dimensional modes of the TELEMAC System were chosen to study the hydrodynamics of the Patos Lagoon. In order to calibrate the TELEMAC-2D model for the lagoon, measurements of salinity, current speed and direction, water elevation and wind speed and direction were carried out simultaneously at three stations in the estuarine area during three days. The model validation was carried out against an independent data set from the 1998 El Nino event. Several two-dimensional simulations were carried out to investigate the main processes controlling the Patos Lagoon hydrodynamics. The model was forced with prescribed river inflow at the top of the lagoon, wind stress at the surface and water elevation at the ocean boundary. The barotropic pressure gradients established between the lagoon and the coastal area as a result of local and remote wind combined with the freshwater discharge, proved to be the main forces controlling the lagoon subtidal circulation, as well as the exchanges between the lagoon and the coast. The local wind dominates the lagoon circulation through the set-up/set-down mechanism of oscillation, whereas the non-local wind drives the circulation in the lower estuary. The entrance channel acts as a filter and strongly reduces tidal and subtidal oscillations generated offshore. Three-dimensional simulations proved to be essential. Studies of the processes involved in the estuarine transverse circulation showed that the wind drives the lateral flow in the shallow areas, whereas in the channel it depends on lateral pressure gradients and channel curvature and geometry. Insights on the estuarine baroclinic circulation indicate the barotropic forces as the main mechanism controlling salt water penetration and salinity structure in the estuary. This study produced valuable information into the forces controlling the circulation of the Patos Lagoon and its estuary. Important issues regarding the capabilities of the TELEMAC System twoand three-dimensional modules were explored, producing a valuable tool for further hydrodynamic and sediment transport numerical modelling experiments.
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Daka, Erema Ransome. "Population differences in the toxic effects of heavy metals to Littorina saxatilis olivi (prosobranchia: Mollusca)." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320573.
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McKelvey, Fionnuala. "Population ecology and fisheries management of the native oyster, Ostrea edulis L. in Lough Foyle." Thesis, University of Ulster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241729.
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George, Christian Robert. "Variation in the erosion threshold of natural intertidal sediments." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261239.
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Julyan, Enrique Edward. "Interrelationship of the fluvial morphology and the salinity of the Great Fish River Estuary." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96952.
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Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The investigation of the interrelationship of the fluvial morphology and the salinity of the Great Fish River Estuary was performed by the combination of a two-dimensional morphological model and a one dimensional advection dispersion module. Two scenarios were defined for investigation, namely Scenarios A and B. Model bathymetry and grid/network for each model and scenario was compiled from topographical information obtained from aerial photos, SRTM data, LIDAR and 24 measured river cross sections of the area from the river mouth up to 27km upstream of the river mouth. Model boundary conditions were developed from empirical formulas and measured data from the Department of Water and Sanitation (DWS). Both models were calibrated with results obtained during field measurement conducted from 5 – 7 May 2012. Scenario A consisted of a long term 5 year morphological simulation (1 May 2007 to 30 May 2012) with manual mouth closure events for identified river low flow periods. Water levels upstream of the river mouth were extracted from the two-dimensional morphological module and used as the downstream boundary condition of the one-dimensional advection dispersion (salinity) model. For scenario B floods with return periods between 1:2 and 1:100 years were simulated in the morphological model. The resultant bathymetries were then used to compile the network and bathymetry of the one dimensional advection dispersion (salinity) model. The different flood resultant bathymetries were then used with equal boundary conditions (representative of the average flow in the river) in the one dimensional salinity model. The predicted salinity was compared for each bathymetry used. From model results distinct trends were observed. During low flow conditions the estuary basin fills with sediments and during floods the sediments are flushed out of the estuary. Large magnitude floods greatly erode the estuary especially in the middle reach, during floods the tidal inlet experiences overtopping and subsequent erosion, the constriction at the tidal inlet is completely destroyed during larger floods. The estuary mouth in its closed state experiences slight overtopping and the mouth is breached during periods of high river flows. The magnitude of salt intrusion depends mainly on the size (the constriction) of the river mouth (tidal inlet). During periods of mouth closure the average salinity in the estuary decreases, average salinity increases if the tidal inlet area is increased. The extent of salt intrusion is approximately 10 km upstream of the river mouth when the mouth is open and the intrusion length increases during spring tides.
AFRIKAANSE OPSOMMING: Die verwantskap tussen die Groot Vis Rivier Estuarium morfologie en sout toestand is ondersoek deur die kombinasie van ‘n twee dimensionele morfologiese model en ‘n een dimensionele sout model. Twee toestande is gedefinieer vir ondersoek naamlik Scenario A en Scenario B. Die area vanaf die rivier mond tot 27 km stroomop van die rivier mond is deur die modelle gesimuleer. Die gemodeleerde area stem ooreen met die area waar gemete rivier-snit diepte metings beskikbaar was, onbrekende data is aangevul met behulp van lugfotos, LIDAR- en SRTM- data. Die model grens toestande is bepaal met empiriese vereglykings asook gemete data vanaf die Departement Waterwese. Beide numeriese modelle was gekalibreer met veld data verkry vanaf 5 tot 7 Mei 2012. Scenario A het behels ‘n langtermyn 5 jaar morfologiese modellering (1 Mei 2007 tot 30 Mei 2012) met toemond toestande gedurende gedefinieerde rivier vloei toestande. Die watervlakke van die twee dimensionele morfologiese model stroomop van die mond is gebruik as die stroomaf grenstoestand van die een dimnesionele model om die effek van die morfologiese veranderinge te inkorporeer in die sout model. Scenario B het behels die simulering van rivier vloede met herhaal periodes tussen 1:2 en 1:100 jaar in die morfologiese model. Die rivier-bodem vlakke verkry van laasgenoemde simulasiesis toe gebruik in die een dimensionele sout model met dieselfde grenstoestande wat ooreenstem met die gemiddelde toestande in die Groot Vis Rivier. Aangesien die grenstoestande dieselfde was en net die rivier-bodem vlakke gevarieer is, kon die effek van vloede op die souttoestand in die estuarium bepaal word. Uit die model resultate kon duidelike tendense waargeneem word. Gedurende lae rivier vloei toestande is die estuarium gevul met sediment en tydens vloede het die sediment weer ge-erodeer en gedeponeer in die oseaan. Groot vloede veroorsaak baie erosie in die estuarium veral in die middel bereik en by die riviermonding. Indien die vloed groot genoeg is word die riviermond vernouing totaal uitgespoel. Die riviermonding in die geslote staat ondervind effense oorstroming en word oopgespoel indien die rivier vloei groot genoeg is. Die graad van die sout indringing in die estuarium hang hoofsaaklik af van die grootte (die vernouing) van die rivier mond. Gedurende toe mond toestande is die gemiddelde sout vlakke in die estuarium laer, wanner die rivier monding groter raak, word die gemiddelde sout vlakke in die estuarium meer. Die omvang van die sout indringing strek tot ongeveer 10 km stroomop van die rivier mond wanneer die mond oop is en die indringing afstand neem toe gedurende spring getye.