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1
Maher, Duarte. "IoT for fresh water quality monitoring". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235179.
Testo completoAbstract (sommario):
Water is one of the most important resources in the world. It has direct impact on the daily life ofmankind and sustainable development of society. Water quality affects biological life and has to obeystrict regulations. Traditional water quality assurance methods, used today, involve manual samplingfollowed by laboratory analysis. This process is expensive due to high labour costs for sampling andlaboratory work. Moreover, it lacks real time analysis which is essential to minimise contamination.This thesis aims to find a solution to this problem using IoT sensors and Machine Learning techniquesto detect anomalies in the water quality. The spatial scalability is key requirement when selecting transmissionprotocols, as sensors could be spread around the water network. We consider solutions readilyavailable or soon to be in the market. The key LPWAN technologies studied are: SigFox, LoRaWANand NB-IoT. In general these protocols have many characteristics essential for fresh water monitoring,like long lasting battery life and long range, however, they have many limitations in terms of transmissiondata rates and duty cycles. It is therefore essential to find a solution that would correctly find anomaliesin the water quality but at the same time comply with limited transmission and processing capabilities ofthe node sensors and above mentioned protocols.A trial sensor is already in place in lake M¨alaren and its readings are used for this study. Supervisedmachine learning algorithms such as Logistic Regression, Artificial Neural Network, Decision Tree, OneClass K-NN and Support Vector Machine (SVM) are studied and discussed regarding the data available.SVM is then selected, implemented and optimised to comply with the limitations of IoT. The trade offbetween false anomalies and false normal readings was also discussed.Vatten ä r en av de viktigaste resurserna i vä rlden. Det har direkt inverkan på mä nsklighetens dagliga liv och samhä llets hå llbara utveckling. Vattenkvaliteten på verkar det biologiska livet och må ste fö lja strikta fö reskrifter. Traditionella metoder fö r vattenkvalitetssä kring, som anvä nds idag, innefattar manuell provtagning fö ljt av laboratorieanalys. Denna process ä r dyr på grund av hö ga arbetskostnader fö r provtagning och laboratoriearbete. Dessutom saknar den realtidsanalys som ä r vä sentlig fö r att minimerafö rorening.Avhandlingen syftar till att hitta en lö sning på detta problem med hjä lp av IoT-sensorer och maskinlä rningsteknik fö r att upptä cka avvikelser i vattenkvaliteten. Den spatiala skalbarheten ä r ett viktigt krav vid val av ö verfö ringsprotokoll, eftersom sensorer kan spridas runt vattennä tverket. Vi diskuterar lö sningar som ä r lä ttillgä ngliga eller snart ska vara på marknaden. De viktigaste LPWAN-teknikerna som studerats ä r: SigFox, LoRaWAN och NB-IoT. Generellt har dessa protokoll må nga egenskaper som ä r nö dvä ndiga fö r ö vervakning av fä rskvatten, som lå ng batterilivslä ngd och lå ng rä ckvidd, men de har må nga begrä nsningar vad gä ller ö verfö ringshastighet och arbetscykel. Det ä r dä rfö r viktigt att hitta en lö sning som skulle hitta anomalier vid hö gt sä kerhet men samtidigt ö verensstä mmer med begrä nsade ö verfö ringsoch bearbetningskapaciteter hos sensorerna och de ovan nä mnda protokoll.En fö rsö kssensor finns redan på plats i Lake Mä laren och dess avlä sningar anvä nds fö r dennastudie.Ö vervakade maskininlä rningsalgoritmer, så som Logistic Regression, Artificial Neural Network,Decision Tree, One Class K-NN and Support Vector Machine (SVM) studeras och diskuteras beträ ffande tillgä ngliga data. SVM vä ljs sedan, implementeras och optimeras fö r att uppfylla IoTs begrä nsningarna.Balansen mellan falska avvikelser och falska normala avlä sningar diskuteras också .
2
Pearce, Ariel Leah. "Fresh Water Scenes in Minoan Art". Diss., Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/451958.
Testo completoAbstract (sommario):
Art HistoryPh.D.
The goal of this dissertation is to provide a comprehensive study of scenes of fresh water in Minoan art from the Middle Minoan II (MM II) through the Late Minoan I (LM I) periods. This dissertation addresses and fills the gap in the scholarship regarding the depiction of riparian environments and the special place of these depictions in Aegean art. It also attempts to clarify the use and function of riverscapes across chronological periods. Rivers, marshes, streams, and springs, appear on a variety of media and fulfil multiple functions from MM II onward. Images of fresh water were used as topographical markers, ornamentation and decoration, and for religious purposes. Moreover, several images suggest that the Minoans may have believed that the realm for the goddess (or one of the goddesses) was a lush, riverscape. A second goal of this dissertation is to clarify and dispose of the term “Nilotic” as a label for images of fresh water in the Aegean. Since its introduction into the literature of Aegean studies in the beginning of the 20th century, the term “Nilotic” has been used inconsistently to describe Aegean scenes of fresh water that may or may not contain Egyptian elements. This assumption has led some scholars to state that Aegean riverscapes are ultimately derived from Egyptian scenes of fishing and fowling because they share similar iconographic elements. Unfortunately, the process of synthesis is important to the understanding of Aegean riverscapes, and iconographic similarities are somewhat superficial. Furthermore, the term has been used without regard for a long-standing tradition of the depiction of riparian environments in Bronze Age Aegean art. To fully address both goals of this project, the origin of individual iconographic elements has been traced through various media, including glyptic art, pottery, and wall painting. Wall paintings from the Cyclades and some Late Helladic IA scenes have been included when appropriate. Whenever possible, categories of riverscapes have been grouped together, but each wall painting, has been examined and interpreted individually. Some unique, highly pictorial, and detailed images in other media have also been addressed separately. Parallels in Egyptian and, in some cases, Near Eastern art have been sought to determine the validity of the term “Nilotic,” and a special study of Egyptian scenes of hunting in the marshes has been conducted in comparison to Aegean scenes. Iconography, synthesis, and context have all been taken into consideration.
Temple University--Theses
3
Aura, Stella M. (Stella Marris). "Fresh water forcing of the North Atlantic". Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56641.
Testo completoAbstract (sommario):
Several numerical experiments are carried out using the Bryan-Cox Ocean General Circulation Model to investigate the variability of the North Atlantic thermohaline circulation under steady, non-zonal, surface forcing and realistic geometry. To this end the annual mean surface forcing fields were derived from the climatological data sets of Levitus (1982), Hellerman and Rosenstein (1983) and, Schmitt et al. (1989). Further, Arctic freshwater flux, an important part of the hydrological cycle within the North Atlantic Deep Water formation region, is taken into account.It is found that under present-day climatological surface forcing the system may oscillate at interdecadal period. The mechanism driving the oscillations is linked to changes in both the horizontal and vertical extent of convection in the northern "Labrador Sea". The structure of the surface freshwater flux forcing plays a major role in both the initiation and sustenance of the interdecadal oscillations. Allowing for a freshwater flux into the northern region of the "Labrador Sea" inhibits the interdecadal variability. The oscillations, however, appear, relatively insensitive to Arctic fresh water transport into the "Greenland Sea".
A detailed three-dimensional discussion of the physics behind the interdecadal oscillations is presented.
4
PICINARDI, Alberto. "Cogeneration of cooling energy and fresh water". Doctoral thesis, Università degli studi di Bergamo, 2011. http://hdl.handle.net/10446/883.
Testo completoAbstract (sommario):
A design simulation of the cogeneration system allowed to chose the best HD unit configuration, while a TRNSYS off-design simulation revealed the main design variables on which to focus the optimization. The optimization study on the design variables was performed by GenOpt, a generic optimization program which minimizes an objective function with respect to multiple variables. This study has been carried out on different objective functions and reveals that maximizing the production of cooling energy means damaging the fresh water production. A compromise solution has been chosen to balance the contrast between cooling energy and fresh water production.
5
PICINARDI, Alberto. "Cogeneration of cooling energy and fresh water". Doctoral thesis, Università degli studi di Bergamo, 2011. http://hdl.handle.net/10446/222125.
Testo completoAbstract (sommario):
A design simulation of the cogeneration system allowed to chose the best HD unit configuration, while a TRNSYS off-design simulation revealed the main design variables on which to focus the optimization. The optimization study on the design variables was performed by GenOpt, a generic optimization program which minimizes an objective function with respect to multiple variables. This study has been carried out on different objective functions and reveals that maximizing the production of cooling energy means damaging the fresh water production. A compromise solution has been chosen to balance the contrast between cooling energy and fresh water production.
6
Crombie, Stephanie. "Carbon and water vapour exchange in a temperate fresh water marsh". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114374.
Testo completoAbstract (sommario):
The ability of wetlands to sequester carbon has given them a considerable amount of attention, especially in light of global climate change. To date, many wetland studies have focused on peatlands, however very few studies have been conducted on marshes. This study used the eddy covariance (EC) technique to measure net ecosystem carbon exchange (NEE) and energy exchange at a temperate freshwater cattail marsh near Ottawa, Canada. The objectives of the study were to use a four year dataset to determine the environmental controls on the variability of carbon and water vapour exchange. The annual cumulative NEE was on average -246 ± 31 gCm-2yr-1 ranging from -216 to -260 gCm-2yr-1. The variability in accumulation between years was a result of the timing of spring and fall transitions in the carbon uptake and the length of the growing seasons, each of which were determined by prevailing weather conditions. Evaluation of the interannual variability indicated that the marsh may be sensitive to carbon (C) losses through enhanced respiration under warmer autumn periods. Maximum daily average values of evapotranspiration (ET) reached 10.75, 9.07, 11.70 and 8.36 mm day-1 in 2005, 2006, 2007 and 2008, respectively. Bowen ratio values varied seasonally with values well below unity during the growing season (May to October) illustrating the dominance of latent heat. Evaluation of the evaporative fraction and Priestley-Taylor α indicated the seasonal importance of ET and mid-season high values of the decoupling coefficient (Ω) indicated that the marsh ET is radiatively driven owing its smooth aerodynamic surface and abundance of water. Overall, the marsh ecosystem was a large annual sink for CO2 as compared to other wetland ecosystems and ET rates were highly dependent on radiative input.La capacité des milieux humides à séquestrer du carbone a beaucoup attiré l'attention, notamment dans le contexte des changements climatiques. À ce jour, bien que plusieurs études aient été menées sur les tourbières, très peu portent sur les marais. Cette étude a utilisé la technique de covariance des turbulences afin de mesurer l'échange écosystémique net (EEN) de CO2 et l'échange d'énergie d'un marécage de quenouilles de l'est de l'Ontario, Canada. Les objectifs de cette étude étaient d'utiliser un ensemble de données de quatre ans afin de déterminer les contrôles environnementaux sur la variabilité des échanges de carbone et de vapeur d'eau. Le EEN annuel cumulé était en moyenne de -246 ± 26,8 gCm-2a-1 allant de -216 à -260 gCm-2a-1. La variabilité de l'accumulation entre les années était le résultat de la synchronisation du printemps et de l'automne au niveau de l'absorption du carbone et de la longueur des saisons de croissance, chacune ayant été déterminée par les conditions météorologiques qui prévalaient. L'étude de la variabilité interannuelle a indiqué que le marécage pourrait être sensible aux pertes de C causées par une augmentation de la respiration au cours de périodes plus chaudes d'automne. Les valeurs moyennes quotidiennes maximales d'évapotranspiration (ET) ont atteint 10,75, 9,07, 11,70 et 8,36 mm jour-1 en 2005, 2006, 2007 et 2008 respectivement. Les valeurs du rapport de Bowen variaient selon la saison, avec des valeurs bien en dessous de l'unité pendant la saison de croissance (mai à octobre), illustrant la dominance de la chaleur latente. Une évaluation de la fraction d'évaporation et du facteur α de Priestley-Taylor indiquaient l'importance saisonnière de l'ET et les valeurs élevées de mi-saison du facteur de découplage (Ω) indiquaient que l'ET du marais est dominé par les radiations en raison de sa surface aérodynamique lisse et de l'abondance d'eau. Dans l'ensemble, l'écosystème du marais était un grand puits de carbone annuel par rapport aux écosystèmes de tourbière et les taux d'ET étaient fortement dépendants de l'apport radiatif.
7
Brettell, Jonathan James. "Walking Severn miles : the affordances of fresh water". Thesis, Aberystwyth University, 2016. http://hdl.handle.net/2160/a3f9f979-c722-48c7-9dbf-45551ca10864.
Testo completoAbstract (sommario):
Following a call from Linton (2010) to think more relationally about water this thesis seeks to explore the infolding and unfolding relations that take-form between bodies around particular characteristics of freshwater. There is a tradition of exploration regarding the sustainability, quality, monitoring and management of water when we encounter research on human associations with fluvial hydrology, and whilst this work is important, this project looks to enrol more nascent and contemporary geographical themes to broaden our understanding of encounters with freshwater landscapes, and take a more relational approach to fluvial geographies. These works then shall address a gap in the geographical literature and describe the personal, pre-personal and affective worlds that emerge when bodies become down by the river. Whilst this is not specifically a walking project, walking the course of the River Severn serves as a trajectory along which processual ideas of bodies on the move shall be mobilised. A series of creatively written segues will link together a sequence of theoretical and conceptually driven site ontologies (Marston et al 2005; Woodward et al 2010) and relations associated with the Severn and freshwater more broadly. The flow and form of the thesis will reflect the multivariant characteristics of water and its varying speeds and slownesses. The chapters will step into puddles, mooch about in a ships graveyard, rethink the source of a river, paddle a coracle and set the scene for how an ontological, relational approach to fluvial landscapes can contribute to geographical thinking. The works will focus on human-nonhuman relations, vibrant materialities and elemental mobilities, in so doing enable further understanding of how we can apprehend sites as moments of coherence in a turbulent world, and contribute to broadening our scope of knowledge of the more-than-human.
8
Tereshchenko, I. M. "The effects of acidification on fresh water life". Thesis, Сумський державний університет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/34942.
Testo completoAbstract (sommario):
Signs that a water body is becoming acidified are clearer water and declining fish populations. The clearness is primarily due to that the humic substances that normally colour the water, precipitate and settle on the lake floor. The main reason for fish stocks declining, both overall and in number of species, is failure to reproduce in acidic water. Many other biological changes occur, too, when the water becomes acidified.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34942
9
Hyer, Eric L. "Fresh Water Ecology Unit for Secondary Education Science Courses". Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1762.pdf.
Testo completo
10
Nash, Brett Jason. "Confluence of the law of fresh water resources and international trade : do Canada’s international trade obligations apply to Canada’s fresh water resources?" Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57777.
Testo completoAbstract (sommario):
This thesis explores whether international trade rules apply to Canada’s fresh water resources. In order to determine if international trade rules apply, in particular the rules contained in GATT 1947, GATT 1994, and NAFTA, three questions are posed by the author. The first question focuses the enquiry on the legal characterization of fresh water resources in the selected international legal instruments to determine the obligations contained in the trade agreements apply. The second question is, if the first question cannot be answered, what other interpretive tools can be employed to come to an answer. Finally, the third question is, if international trade obligations apply the the bulk export of fresh water resources, are there any exemptions which can be employed to limit or prohibit the bulk export of the resource. In order to answer these questions, the author applies a traditional legal doctrinal analysis. This provides a method of analyzing the legal texts of the international agreements and other legal materials in an orderly and systematic manner. Using this methodology, the author engages with the primary materials to determine the ordinary meaning of the words and phrases used in the texts. In addition to the analysis of the legal texts, the author reviews the history of the development of Canada’s international trade and foreign policy through the lens of the international relations theory of exogenous shock. By using the theory of exogenous shock as an interpretive aid, the author is able to provide justification in concluding that the preferred interpretation that Canada’s international trade obligations found in GATT and NAFTA do not apply to Canada’s fresh water resources.Law, Peter A. Allard School of
Graduate
11
Brooks, Jenkins Gareth. "Amelioration of acidity in fresh waters : individual to ecosystem level responses". Thesis, Queen Mary, University of London, 2015. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8981.
Testo completoAbstract (sommario):
The extensive acidification of fresh waters across Europe and North America during the 20th century led to extensive and widespread loss of species, which fundamentally changed the structure of resident communities. While attempts to limit or halt acidifying emissions have been successful in reversing the chemical consequences of acidification, any corresponding biological recovery has been patchy at best. The main aim of this thesis was to investigate potential ecological constraints on this biological recovery, ranging from interactions between individuals to ecosystem-level processes, using a model stream system that has been extensively studied for over 40 years. I used a combination of long-term survey data and experiments, both in the field and the laboratory, to provide evidence that the lag in recovery of acidified aquatic communities is due to intrinsic resistance to re-colonisation by acid-sensitive species, as a result of both direct and indirect interactions between predators and prey. However, there is also evidence of recovery at an ecosystem level, with rates of microbial decomposition increasing – a key link in the transfer of energy to higher trophic levels, which could be facilitating population increases in large-bodied predators. These findings increase our understanding of the drivers which govern the structure and function of ecological networks in response to an important climatic stressor. This is especially relevant given the rapid industrialisation of countries such as India and China, which could well soon experience anthropogenic acidification on a significant scale.
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Yoder, Madonna K. "Lower Charles River bathymetry : 108 years of fresh water". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/114326.
Testo completoAbstract (sommario):
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (page 22).
The Lower Charles River has been a heavily utilized urban river that runs between Cambridge and Boston in Massachusetts. The recreational usage of the river is dependent on adequate water depths and there have been no definitive prior studies on the sedimentation rate of the Lower Charles River. The river transitioned from tidal to a freshwater basin in 1908 and the study area for historical comparisons was from the old Charles River Dam to the Boston University Bridge. This study surveyed the river, digitized three prior surveys that spanned 114 years, calculated volumes and depth distributions for each survey, and estimated sedimentation rates from fits to the volumes over time. The average sedimentation rate is estimated as 5-10 mm/year, which implies 1.8-3.5 feet sedimentation since 1908. Sedimentation rates and distributions are necessary to develop comprehensive management plans for the river.
by Madonna K. Yoder.
S.B.
13
George, Alabodite M. "Numerical simulation of warm discharge in cold fresh water". Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/27376.
Testo completoAbstract (sommario):
Buoyant plumes in cold fresh water are of interest because of the possibility of buoyancy reversal due to the nonlinear relation between temperature and density in water. Thus an initially rising plume may become a fountain. This project aims to mathematically model such plumes and fountains using numerical simulation by the means of a commercial software, Comsol Multiphysics. Both turbulent and lam- inar cases were investigated in different geometries, and with the assumption that density is a quadratic function of temperature. The turbulent flow cases as con- sidered here in this thesis are relevant to practical applications such as industrial discharge in cold lakes: whereas, the laminar flow case relates to laboratory experi- ments which are typically at scales too small for the flow to be turbulent. Previous investigation on warm discharge placed more attention on the biological implications of the spread along the lake bed, and not interested in analysing the dynamics of such flow, which turns out to be our focus. Furthermore, investigations on buoyant plumes that become negatively buoyant at later time (fountain flow) as considered previously, are based on the assumption that density is a linear function of tem- perature: where entrainment always reduces buoyancy. Whereas, the consideration of the temperature of maximum density is crucial and realistic in many practical situations, especially the power station warm discharge. Mixing is then bound to produce a mixture that is denser than both the discharge and the ambient water if receiving water is less than Tm: where this situation differs from plumes with linear mixing properties. Therefore, our focus is to better fathom the behaviour of warm discharge so as to give a detailed description of the flow, and also to observe buoyancy reversal whenever water that is denser than both the discharge and the receiving water is produced. The simulations were carried out for Prandtl number Pr = 7 & 11.4 and over the ranges of Froude number 0.1 ≤ Fr ≤ 5 and Reynolds numbers 50 ≤ Re ≤ 106, with source temperatures that are assumed to be higher than the temperature of maximum density Tm, and the ambient water below the Tm. Our results show some distinct behaviours from those experimental investigations by Bukreev, who also considered warm discharge where water that has temperature above the temperature Tm is initiated into a medium below Tm. The results here also showed some differences from those investigations with the linear dependence relation assumption.
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Gigante, Bethany Marie. "SALINE ADAPTATION OF THE MICROALGA Scenedesmus dimorphus FROM FRESH WATER TO BRACKISH WATER". Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1382355969.
Testo completo
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Drysdale, Lewis A. "Arctic fjords : simplified modelling and the role of freshwater". Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=237133.
Testo completoAbstract (sommario):
Defining the role of freshwater in a fjord is important to further the understanding of seasonal physical variability in fjordic systems because the variability of freshwater flux is a key control on fjord oceanography, yet information on freshwater inputs to Svalbard fjords is currently lacking. In this study, two methods of studying fjords are utilised. Firstly, seawater samples and oceanographic profiles were collected from four fjords and shelves around the high-Arctic Svalbard archipelago between September 2013 and April 2015. Analysis of the seawater samples showed that surface meteoric water in a glaciated west-Svalbard fjord was present in quantities up to four times as much (∼18%) assea-ice melt (∼5%). In comparison, a north-Svalbard fjord had more than twice as much sea-ice melt (∼5%) as meteoric water (∼2%). Four contrasting regions of freshwater infuence around the Svalbard archipelago were established, defined by their freshwater processes. Further analysis of data suggest that coastal currents act as an upstream freshwater source, and are also enhanced by freshwater along their path. Upper layer circulation, meanwhile, was seen to be an important mode of dispersal of freshwater inputs from smaller inlets. Secondly, a box model was modified by the inclusion of a sea ice model and was run to understand the leading-order processes and mechanisms observed in Arctic fjords. Model results were successfully validated against four years of oceanographic data from a mooring deployed between 2008–2013 in a restricted exchange fjord on Svalbard and represented the seasonal cycle of a high-Arctic fjord including sea-ice growth and convection. The model showed that varying the sill geometry of a high-Arctic fjord impacts the formation of sea-ice and the dominant modes of exchange. The model also showed that warming of the sub-surface temperature causes excess heat inside fjords, which impacts on sea-ice production and (although not shown) is highly likely to cause accelerated melting of tidewater glaciers.
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Bailey, Eva Machelor. "Processes Affecting Macroalgal-Seagrass Dynamics in the York River, Virginia". W&M ScholarWorks, 1998. https://scholarworks.wm.edu/etd/1539617969.
Testo completo
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Ledwin, Jane M. "Sedimentation and its Role in the Nutrient Dynamics of a Tidal Freshwater Marsh". W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539617586.
Testo completo
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Galler, John J. "Medium- and Long-Term Changes in Fluvial Discharge to the Sea: The Yellow River Case Study". W&M ScholarWorks, 1999. https://scholarworks.wm.edu/etd/1539617746.
Testo completo
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Wooden, Eric Anthony. "Tidally Driven Patterns of Nekton Distribution and Utilization of a Tidal Freshwater Marsh at Morris Creek (Chickahominy River, Virginia)". W&M ScholarWorks, 1999. https://scholarworks.wm.edu/etd/1539617979.
Testo completo
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Mahon, Susan Alexandra. "Distribution of Freshwater Amphipoda in the Lake Matoaka/College Woods Area, Williamsburg, Virginia". W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539626095.
Testo completo
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Zehmer, John Kinsley. "Calcium as a Limiting Factor in the Distribution of the Amphipod Gammarus pseudolimnaeus". W&M ScholarWorks, 1998. https://scholarworks.wm.edu/etd/1539626165.
Testo completo
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Fairman, Christy Michelle. "Using an Occupancy Modeling Framework to Test the Effects of Habitat Variables on Pond Occupancy of Mabee's Salamander (A mabeei) and Marbled Salamander (A opacum)". W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539626882.
Testo completo
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Postaski, Lindsey L. "Life History and Ecology of the Freshwater Amphipods Gammarus pseudolimnaeus and Gammarus fasciatus in Southeastern Virginia". W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539626926.
Testo completo
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Neubauer, R. Joseph. "The Relationship between Dominant Macrobenthos and Cyclical Hypoxia in the Lower York River". W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539617659.
Testo completo
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Packett, Carmen Rebekah. "Effects of Salinity and Nitrogen on the Distribution and Growth of Phragmites australis along the Rappahannock River". W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539626837.
Testo completo
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Reay, William G. "Subsurface Hydrodynamics and Nutrient Exchange within an Extensive Tidal Freshwater Wetland". W&M ScholarWorks, 1989. https://scholarworks.wm.edu/etd/1539617595.
Testo completoAbstract (sommario):
Located between upland and riverine systems, extensive tidal freshwater wetlands are influenced by a variety of recharging water sources and their respective nutrient contents. Conversely, tidal wetlands discharge interstitial waters and solutes to surface waters during periods of aerial exposure. Geohydrologic and model simulation methodology were utilized in order to aid in the understanding of wetland subsurface flow dynamics, its influence upon pore water nutrient chemistry, and its role in nutrient exchange with adjacent surface waters. Interstitial water nutrient chemistry was monitored along three transects extending from the uplands to the creekbank edge. Surface waters were also monitored throughout the 13 month study period.
Measurements of soil dry bulk density, percent organic matter, fiber content, and horizontal hydraulic conductivity were conducted along a 118 meter transect from the creekbank edge to the high marsh/upland interface. Results indicate vertical and lateral heterogeneity of these physical and hydraulic soil properties within the upper one meter soil profile. Multivariate statistical techniques best described the transect as four separate soil types. General regions of soil types followed wetland elevational regions, these include: the creekbank, levee, low marsh flat, and high marsh regions. Fiber content was identified as the measured parameter which best explained variations in wetland soil permeability. Vertical and horizontal hydraulic head fluctuations were monitored utilizing piezometer/well arrays along the 118 meter transect. Direct measurement of interstitial water seepage flow from the subaquaeous portion of the creekbank to adjacent surface water was determined. Model simulation of subsurface hydrodynamics were made in order to provide water table fluctuations, estimates of horizontal seepage, and pore water budgets along the transect. Field measurements of marsh surface elevations and hydraulic soil properties were incorporated into the model to allow for comparison between simulated and observed results.
Spatial variations in soil properties, and subsurface hydrodynamics indicate that an extensive tidal freshwater wetland cannot be considered as a homogeneous unit. It may be described more accurately as three distinct, yet interactive regions (creekbank, low marsh flat,and high marsh), with varying potentials for surface and interstitial water exchange. The creekbank, experiencing large water table oscillations and hydraulic gradients, was the most dynamic and tidally influenced region. These hydrodynamic characteristics resulted in substantial subsurface water transport and dilution of interstitial waters by recharging surface waters within the creekbank region. Due to extremely low hydraulic gradients and ponding of water, horizontal seepage was minimal within the low marsh flat. Moderate hydraulic gradients in conjunction with highly permeable soils were conducive for significant horizontal seepage within the high marsh. Hydrologic evidence indicates a potential for nutrient rich shallow groundwater recharge within the high marsh region. Sensitivity analysis within the creekbank region indicates that aquifer depth exhibits the largest influence on interstitial water discharge followed by soil permeability and specific yield properties of the aquifer respectively. Inverted results, as those found within the creekbank region, were obtained for the high marsh region.
Interstitial water nitrogen and total phosphorus levels were variable and a function of depth, location, and time. However, several generalities and patterns appeared relatively consistant. Creekbank pore waters were relatively enriched with oxidized inorganic forms of nitrogen relative to low and high marsh regions. Creekbank ammonium, total nitrogen and phosphorus interstitial pools were intermediate, whereas, dissolved organic nitrogen levels was the lowest of the three regions sampled. The low marsh flat was inorganic nitrogen poor, and intermediate with respect to dissolved organic nitrogen, relative to creekbank and high marsh regions. Pore waters within the low marsh were significantly enriched with dissolved total phosphorus as compared to the creekbank and high marsh regions. High marsh interstitial waters displayed reduced levels of nitrate and nitrite, while levels of ammonium, dissolved organic and total nitrogen were elevated in relation to the creekbank and low marsh flat. Interstitial total phosphorus levels within the high marsh were significantly lower than the low marsh and approximately equal to the creekbank region. The role and influence of subsurface hydrodynamics upon pore water nutrient concentrations and spatial variations are discussed.
Spatial and temporal potential patterns of nutrient exchange between surface water and pore waters of various wetland regions are identified. Dissolved oxidized inorganic forms of nitrogen were imported throughout the sampling period by the creekbank, low marsh flat, and high marsh regions. Ammonium flux, due to seepage , was predominantly from the wetland to surface waters; the high marsh exhibited a greatest potential for ammonium export. The high marsh was a source of dissolved organic nitrogen throughout the study, while the low marsh flat and creekbank regions may best be characterized as sources during winter, spring, and summer months, and potential sinks during the fall. The high marsh exhibited the potential to export dissolved total nitrogen throughout the year, whereas, the low marsh flat and creekbank exhibit export potential during spring and summer months. Patterns of total phosphorus exchange were from high marsh, and low marsh regions throughout the year, while exchange between creekbank and surface waters was minimal and temporally variable. Hydrodynamics within each wetland region must be considered in conjunction with pore water chemistry, in order to fully understand nutrient and solute transport potentials.
27
Shields, Erin C. "Influences of Habitat Conditions on Submerged Aquatic Vegetation Development in the Chickahominy River and Other Virginia Tributaries of the Chesapeake Bay". W&M ScholarWorks, 2008. https://scholarworks.wm.edu/etd/1539617869.
Testo completoAbstract (sommario):
Recently, there has been an expansion of submerged aquatic vegetation (SAV) in the tidal fresh and oligohaline portions of lower Chesapeake Bay tributaries. Much like the resurgence seen in the Potomac in the 1980’s, this spread of SAV in Virginia systems such as the Mattaponi, Pamunkey and Chickahominy seems to have been initiated by the introduction and spread of the invasive species Hydrilla verticillata, and appears to have been rapid. However the resurgence in the Piankatank has occurred in the absence of the introduction of this species. The factors that are influencing the growth of SAV in these tributary environments, including water quality and habitat conditions as well as the potential for interspecific competition between H. verticillata and the other SAV species in these regions are not well known. Annual aerial mapping surveys of the Chickahominy River were used alongside historical water quality data to investigate the patterns and rates of SAV bed development, and the relationships between this development and water quality conditions. Field investigations were performed in order to better understand the seasonal community dynamics relative to water quality conditions and interspecific competition. Historical analysis, field monitoring and field experimentation all showed salinity and turbidity to be the main factors controlling SAV abundance and species distribution along the Chickahominy River. Historical analysis of the Chickahominy River revealed a decline in SAV abundance in 2002, which corresponded with seasonal mean salinities of 4.1 psu. SAV abundance from 1998-2007 showed a significant correlation with vegetation emergence period secchi depth, in which secchi depths of 0.3 meters, the lowest of the time period, occurred during the 2002 SAV decline. Field data showed species zonation, in which H. verticillata was the overall dominant species, but was limited to the upper portion of the river where salinity intrusion remained below 2 psu throughout the growing season. Najas minor was dominant in the lower portion of the river where salinities reached over 4 psu in October. Salinity was the best predictor for H. verticillata’s biomass difference between the upper and lower river. SAV in the Chickahominy was able to grow in a wide range of conditions, with total suspended solids and chlorophyll a concentrations at times greater than 20 mg l-1 and 40 μg l-1, respectively, and sediment organic content ranging from less than 1% to greater than 25%. Comparisons with the Mattaponi and Piankatank rivers revealed ideal habitat for H. verticillata growth in the Mattaponi, where salinities along the vegetated reach of the upper river did not extend above 1 psu. On the other hand, this species was not found growing in the Piankatank, where salinities in the very upper portion of the river reached 3.5 psu. Finally, a field species removal experiment demonstrated that environmental conditions rather than interspecific competition were most important in determining plant performance, as both H. verticillata and N. minor exhibited poor growth in the lower river site, which had higher salinity and turbidity levels than the upper river site.
28
Richardson, Glen. "Climate response to fresh water forcing in the Southern Ocean". Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432442.
Testo completo
29
McInnes, Sandra J. "Taxonomy, biodiversity and biogeography : Tardigrada and Antarctic meiofauna". Thesis, Anglia Ruskin University, 2010. http://arro.anglia.ac.uk/216030/.
Testo completoAbstract (sommario):
The main subject of my papers has been the phylum Tardigrada, with particular emphasis on the Antarctic fauna. While this is one of the ‘lesser known phyla’ the group forms an important element of Antarctic non-marine ecosystems. My work has centred on four interrelated themes: i) taxonomy, predominantly Tardigrada and with an Antarctic bias though including wider global species and high taxon groupings (I have also worked on other taxa such as Fungi-imperfecti and freshwater invertebrates); ii) biodiversity of tardigrades, particularly Antarctic habitats; iii) data-based studies based on the terrestrial Tardigrada and Antarctic freshwater crustaceans; and iv) biogeographic analysis of these databases. The thesis presented consists of papers published in major, peer-reviewed journals, along with book chapters published and in press. Several of my papers have been cited 10-30 times according to the ISI Web of Science citation system. Highlights of my work include being the first to publish a paper on the global terrestrial biogeography of a phylum and showing the extant limno-terrestrial tardigrade fauna reflect the early tectonic break-up of the Laurasia, West and East Gondwana super continents between 65 and 135 million years ago.
30
McInnes, Sandra J. "Taxonomy, biodiversity and biogeography: Tardigarda and Antarctic meiofauna". Thesis, Anglia Ruskin University, 2010. https://arro.anglia.ac.uk/id/eprint/216030/1/McInnes_Thesis_2010.pdf.
Testo completoAbstract (sommario):
The main subject of my papers has been the phylum Tardigrada, with particular emphasis on the Antarctic fauna. While this is one of the ‘lesser known phyla’ the group forms an important element of Antarctic non-marine ecosystems. My work has centred on four interrelated themes: i) taxonomy, predominantly Tardigrada and with an Antarctic bias though including wider global species and high taxon groupings (I have also worked on other taxa such as Fungi-imperfecti and freshwater invertebrates); ii) biodiversity of tardigrades, particularly Antarctic habitats; iii) data-based studies based on the terrestrial Tardigrada and Antarctic freshwater crustaceans; and iv) biogeographic analysis of these databases. The thesis presented consists of papers published in major, peer-reviewed journals, along with book chapters published and in press. Several of my papers have been cited 10-30 times according to the ISI Web of Science citation system. Highlights of my work include being the first to publish a paper on the global terrestrial biogeography of a phylum and showing the extant limno-terrestrial tardigrade fauna reflect the early tectonic break-up of the Laurasia, West and East Gondwana super continents between 65 and 135 million years ago.
31
Charles, Sean P. "The Development of Ecological Functions in Created Forested Wetlands". W&M ScholarWorks, 2013. https://scholarworks.wm.edu/etd/1539617942.
Testo completoAbstract (sommario):
Wetland mitigation has become a 2.4 billion dollar per year industry in the U.S. and in Virginia it leads to the replacement of 77 ha of palustrine forested wetlands (PFWs) per year with mitigation wetlands, including created forested wetlands (CFWs). Mitigation hinges on the idea that compensation wetlands lead to “no net loss of wetland function” when compared to impacted wetlands. We assessed the functions of provision of habitat and biogeochemical functions associated with production of biomass, the retention and removal of nutrients and the accumulation of soil C over 8 years in seven CFWs of approximately 11 and 20 years and compared them to natural reference wetlands (NRWs). CFW plant communities were similar to NRWs in all measured parameters in the herbaceous and shrub/sapling strata and in all strata combined. However, non-native dominance showed a significant positive linear relationship with CFW age. In the tree strata, 11 year old (yo) CFWs had lower richness than NRWs and both age classes of CFWs had lower FQI than NRWs. NRWs held 10 to 20 times more carbon in woody biomass than CFWs. Tree species composition was significantly different between CFWs and NRWs, however NRW trees were similar to CFW saplings. 11 yo CFWs held lower percentages of C, N and P and had higher Db than NRWs in both the 0-10 and 10-20 cm depth. 20 yo CFWs developed similar levels of %C, %P, bulk density (Db), and nutrient ratios in the surface and displayed rapid increases in %C and %N over 8 years. However, CFWs offered 45% lower soil total soil C storage and 50% lower %N. Furthermore, all CFWs stored lower nutrient levels than NRWs in the 10-20 cm soil depth. We found that FQI correlated positively with total C accumulation rates in woody biomass and soil C, indicating that biogeochemical function and the provision of habitat can be complimentary in CFWs. Finally, 11 and 20 yo CFWs adhered to the regulatory performance standards established for Virginia in terms of stems per ha and wetland indicator status, but all wetlands (including NRWs) failed to achieve <5% non-native species cover.
32
Bradley, Cassie D. "The Impacts of Shoreline Development on Shallow-Water Benthic Communities in the Patuxent River, MD". W&M ScholarWorks, 2011. https://scholarworks.wm.edu/etd/1539617905.
Testo completoAbstract (sommario):
Natural coastal habitats throughout Chesapeake Bay are increasingly threatened with shoreline modification due to population growth and rising rates of development. The replacement of these natural coastlines with hardened structures such as seawalls (bulkheads) and stone revetments (riprap) not only compromises vegetation at the land-water interface, but also can influence several elements of local aquatic food webs. Effects of these alterations have been well-studied with respect to fish assemblages and intertidal communities, particularly in conjunction with larger-scale watershed development, and recently, interest has shifted toward investigation of the effects of shoreline development on subtidal benthic infaunal communities.This study evaluated the direct, local impacts of bulkhead and riprap compared to natural marsh shorelines, as well as the effects of sediment characteristics, predator abundance, and system-specific physical features on benthic infauna in the Patuxent River, Chesapeake Bay. Forty-five sites were divided among three shoreline types and distributed across three main river zones. At each site, a benthic infaunal suction sample (3-mm mesh), push-core sample (500-μm mesh), sediment samples, water-quality measurements, and trawls for predators were taken. Samples were sorted to determine density, diversity, and biomass of infaunal organisms. Data were assessed using an Information-Theoretic approach (AIC analysis) to determine the most influential variables, of those measured, on the infaunal community for two benthic data sets: 3-mm-suctions and 500-μm-cores. Results from these analyses on 3-mm samples suggested that shoreline type was the best predictor of diversity, while wave energy, sediment chlorophyll concentration, sediment type, and predator abundance best predicted density and biomass. Benthic responses within the 500-μm dataset were not strongly affected by shoreline type. Rather, responses were best predicted by sediment chlorophyll, wave energy, sediment type, predator abundance, and sediment organic carbon (TOC) content.Results indicate that, compared to other Bay tributaries, the Patuxent River is a relatively degraded system. The small range in long-term responses of Patuxent infauna from previous work provides a possible explanation as to why I was unable to see significant differences in infaunal response among shoreline types in the current study (i.e., there was little scope for change by shoreline in the system as a whole). However, I suggest that natural marsh habitats are healthier subsystems of the Patuxent River, due to the greater variety of infaunal feeding guilds and higher infaunal biomass observed at these compared to hardened sites. Higher predator abundance was associated with higher infaunal biomass at natural marsh sites in both size fractions, suggesting the bottom-up control of higher-trophic-level species in this system, as predators seek out suitable prey items. Given these observations, and the fact that influential variables such as wave energy, sediment nutrient and chlorophyll content, predator abundance, and sediment type may vary according to shoreline type, the replacement of natural shoreline with hardened structures will lead to complex changes in subtidal benthic communities in Chesapeake Bay tributaries and should be minimized to maintain qualities of the natural system.
33
Christensen, Tyler. "Meta-Analysis and Modeling of Benthic Oxygen and Nutrient Fluxes". W&M ScholarWorks, 2002. https://scholarworks.wm.edu/etd/1539617788.
Testo completo
34
Tuckey, Troy D. "Variability in juvenile growth, mortality, maturity, and abundance of American shad and blueback herring in Virginia". W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539616883.
Testo completoAbstract (sommario):
Young-of-year (YOY) population dynamics of American shad and blueback herring in Virginia's rivers were examined with an emphasis on variability in growth and mortality rates. In addition, an analysis was conducted to relate juvenile abundance indices of American shad to adult indices to establish a stock-recruitment relationship. to accomplish the stock recruitment relationship, an additional study that examined maturation schedules and inter-annual variability in maturation schedules among stocks was performed. Results of population dynamics studies found that growth and mortality rates of American shad and blueback herring varied by river and year and that conspecific abundance was an important factor in predicting size at the end of summer indicating density-dependent regulation of growth. For both species, instantaneous growth was highest at 40 d and decreased by 100 d as water temperatures decreased each year. American shad Mortality rates increased from 2005 to 2007 with highest rates observed in the James River, while mortality rates for blueback herring had no clear pattern. Large year-classes of Alosa spp. that are smaller in size prior to emigration into the coastal ocean may experience higher mortality rates resulting in recruitment stabilization. Despite the close proximity of four river systems studied, there were persistent differences in growth and mortality rates that support observed trends in year-class strength. High mortality rates observed in the James River support the observation of almost complete recruitment failure of wild American shad in this system. Furthermore, low mortality rates observed in the Rappahannock River are consistent with an increasing trend in recruitment of maturing females, while lower mortality rates and similar growth rates observed in the Mattaponi River compared with the Pamunkey River support long term observations of greater juvenile production of American shad in the Mattaponi River. Young-of-year blueback herring recruitment in Virginia rivers was an episodic process with multiple peaks observed throughout summer indicating that cohorts were not fully vulnerable to sampling and that there may be movement out of adjacent habitats. Maturation of American shad showed consistent patterns with most American shad mature by age 5. However, year-class specific estimates ranged from 50% to 85% mature in the James River, from 59% to 79% in the Rappahannock River, and from 60% to 87% in the York River. Based on current monitoring, the age of full recruitment to the staked gillnet fishery is age 5, corresponding to the age when the largest proportion of the population reaches maturity. Harvest of age 5 females in the historical fishery was probably a contributing factor to its collapse during the 1980s. Persistent differences in maturity schedules of American shad between the James and York rivers, and to a lesser extent with those from the Rappahannock River, show that neighboring stocks that experience similar climate regimes can have stock-specific maturity patterns that persist through time. Using juvenile abundance indices (or hatchery release in the case of the James River), the estimated maturity schedule, and estimated adult mortality rates, resulted in a predicted index that matched observed trends from 1998 to 2006 for three stocks of American shad. This study demonstrates that population dynamics of juvenile Alosa spp. is highly variable in a temporal and spatial context involving density-dependent processes that act to regulate year class production.
35
Atran, Steven M. "Fluctuations in the Catchability Coefficient of Atlantic Menhaden, 1968-1982". W&M ScholarWorks, 1986. https://scholarworks.wm.edu/etd/1539617568.
Testo completo
36
Brust, Jeffrey C. "The Effects of a Regulatory Gear Restriction on the Harvest of the Recruiting Year Class in the offshore Sea Scallop, Placopecten magellanicus, Fishery". W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539617711.
Testo completo
37
Kerstetter, David. "Description and evaluation of the United States coastal pelagic longline fishery interactions with target and non-target species in the western North Atlantic". W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539616711.
Testo completoAbstract (sommario):
Eighty-five monitored sets were used to investigate the interactions of pelagic fishes with commercial pelagic longline gear in the western North Atlantic during the fall mixed species fishery north of Cape Hatteras, North Carolina, and the spring swordfish fishery in the southern Gulf of Mexico and northern Caribbean Sea. This dissertation incorporates four components: (1) direct analyses of longline gear behavior using small time-depth recorders, (2) comparisons of catch rates and mortality of all species caught on size 16/0 non-offset circle and size 9/0 straight-shank J-style hooks, including analyses of time-of-capture utilizing electronic hook time recorders, (3) an evaluation of post-release survival of white marlin captured by longline gear using pop-off satellite archival tags (PSATs), and (4) a description of two PSATs attached to white marlin and subsequently ingested by sharks. Data indicated that pelagic longline gear in the shallow coastal U.S. fishery is frequently in motion, even after hooks were presumed to have settled at depth. Effective fishing depths of the gear under several configurations were also shallower than predicted by commonly used catenary curve-based depth calculations. Catch rates between circle and J-style hook types were similar for most species, with only pelagic rays in the fall fishery showing an increased catch rate with J-style hooks. Yellowfin tuna and dolphinfish caught on circle hooks in the fall fishery were larger than those caught on J-style hooks. Most species were more commonly caught in the mouth with circle hooks rather than internally. A total of 28 white marlin were tagged with PSATs. Transmitted data from 17 of 19 reporting PSATs demonstrated survival following release. Estimates of post-release survival range from 60.7% (assuming that non-reporting tags were mortalities) to 89.5% (excluding non-reporting tags from the analysis). Two white marlin PSATs reported data consistent with predation or scavenging by sharks, including ingestion of the tags for seven and ten days respectively. This suggests that non-reporting PSATs may also be the result of unreported biological interactions.
38
Ralph, Gina M. "Quantification of Nursery Habitats for Blue Crabs in Chesapeake Bay". W&M ScholarWorks, 2014. https://scholarworks.wm.edu/etd/1539616819.
Testo completoAbstract (sommario):
The blue crab is an iconic species in Chesapeake Bay, supporting important commercial and recreational fisheries and functioning as a critical link in the food web. Structurally complex habitats are often cited as nurseries for the blue crab, and other commercially important fish and crustacean species, by providing enhanced growth and survival for juveniles. I quantified the value of shallow habitats as nurseries for blue crabs through field studies and a demographic model. In Chapter 2, I utilized a two-year juvenile survey in vegetated habitats of the lower Bay to examine the effect of habitat complexity on the density of juvenile blue crabs. The functional relationship between seagrass cover and juvenile density was exponential, such that there were proportionally more crabs per unit increase in cover of vegetated habitat at high percent cover than at low percent cover. The relationship varied spatially, with higher densities on the eastern shore, and between the two years. The high spatial and annual variability led to questions about how habitat utilization varied throughout the recruitment season. I addressed the timing of recruitment and migration between habitats in Chapter 3 through the development of a survey of shallow habitats in the York River with high temporal and spatial resolution. The study provided evidence for a carrying capacity of juvenile blue crabs in vegetated habitats at 10-15 crabs m2. I found substantially higher densities of small juveniles in shallow unvegetated habitats than previously documented, which suggested that the current paradigm for blue crab recruitment requires modification to include the importance of shallow unvegetated habitats for small juveniles. In Chapter 4, I examined the effect of habitat utilization patterns as a function of age or ontogeny on the blue crab stock assessment by comparing juvenile density and abundance estimates from shallow vegetated and unvegetated habitats to estimates from deep habitats sampled by the primary survey for the stock assessment. Juvenile abundance was very high in both shallow habitats despite the relatively smaller area, thus suggesting that the winter dredge survey substantially underestimated the abundance of juvenile crabs. If this bias is inconsistent inter-annually, potentially as a function of temperature, then stock assessments may be producing biased reference points. Finally, I developed an exploratory habitat-specific demographic model to quantify the effects of habitat on population fitness in Chapter 5. Under all fishing mortality rates, including a complete fishing moratorium, the population growth rate was less than 1 when only unvegetated habitat was present; the increased survival of age-0 crabs provided by vegetated habitats led to increases in the population growth rates. The vegetated habitats provided a buffer from fishing mortality; that is, as the survival of juveniles increased in vegetated habitats, the population could sustain higher fishing mortality rates while still remaining stable or even increasing. Shallow vegetated habitats substantially influence juvenile blue crabs and the overall population growth rate. It is essential that these habitats be considered in future explorations of the dynamics of blue crabs, as well as other species that exhibit ontogenetic shifts in habitat utilization.
39
Sutter, Lori A. "Effects of Saltwater Intrusion on Vegetation Dynamics and Nutrient Pools in Low-Salinity Tidal Marshes, Pamunkey River (Virginia, USA)". W&M ScholarWorks, 2014. https://scholarworks.wm.edu/etd/1539616868.
Testo completoAbstract (sommario):
This study investigated vegetation changes in a former tidal freshwater marsh (TFM) to determine the role that salinity intrusion plays in vegetation dynamics. Field observations along a narrow salinity gradient in the Pamunkey River revealed that vegetation is shifting to fewer dominants with increasing salinity. Two remaining dominants, Peltandra virginica and Zizania aquatica (hereafter Peltandra and Zizania, respectively), had variable net CO2 assimilation throughout the growing season. Peltandra net CO2 assimilation declined both over the growing season and in marshes with higher salinity; whereas, Zizania generally increased over the growing season peaking in late summer. The same species' tissue nutrients tracked similarly when compared across marshes of different salinity throughout the season, suggesting that the plants have adapted to their environment. Soils, however, contained higher carbon (C) and nitrogen (N) in a TFM relative to higher salinity marshes across years and within a single season. The soil N: phosphorus (P) ratio is relatively stable and well above 16:1 in the TFM, suggesting P-limitation. The other marshes appeared to be in transition with high fluctuations throughout the season and variability within the marsh. Soils responded to changes in salinity faster than vegetation by adsorbing or releasing nutrients. A mesocosm testing plant traits subjected to four low salinity levels found Spartina alterniflora (hereafter Spartina) unresponsive to salinity ranging from 0 to 6, although CO2 assimilation decreased between treatments fresh and 6. Two TFM species, Peltandra and Leersia oryzoides (hereafter Leersia ), responded to salinity over 2 with decreases in aboveground and belowground biomass. The same two species exhibited an improvement in biomass quality (measured by C:N and C:P) over the salinity gradient, and both held greater N and P in the vegetation pool relative to Spartina. The pool of nutrients held in vegetation may shift with salinity intrusion, and the enhanced biomass quality may lead to greater herbivory due to improved palatability. A second mesocosm study paired Spartina, a facultative halophyte, with each of three TFM species: Peltandra, Leersia, and Phragmites australis (hereafter Phragmites). Spartina outperformed Peltandra in all aspects measured -- both aboveground and belowground. In the presence of Leersia, Spartina offered mixed responses, but Phragmites changed Spartina responses considerably. The results of this experiment suggest that Spartina can succeed in less benign environments in the presence of at least some species. A field manipulation excluding insect herbivory within treatments in three marshes along a salinity gradient found that overall biomass did not respond to the removal of insect herbivory, except for Peltandra in Cumberland Marsh (TFM). Peltandra biomass in TFM exclosures was approximately double that of controls, but this result was not significant in other marshes. Zizania N-content was higher in exclosures, suggesting a loss of this nutrient with herbivory, perhaps from rebuilding scarred tissue and/or loss through guttation. Given Peltandra's salt intolerance and Spartina's ability to outperform common species, it is possible that Sweet Hall Marsh, a previous TFM transitioning to an oligohaline marsh, will become a Spartina-Phragmites marsh in the future driven by bottom-up controls.
40
Delaney, Glenn Roger. "Morphometric and Meristic Stock Identification of Summer Flounder (Paralichthys dentatus)". W&M ScholarWorks, 1986. https://scholarworks.wm.edu/etd/1539617560.
Testo completo
41
Brotman, Mark J. "A Comparison of Grow-Out Methods for the Bay Scallop, Argopecten irradians irradians, at Two Sites in Virginia". W&M ScholarWorks, 1992. https://scholarworks.wm.edu/etd/1539617644.
Testo completo
42
Dawson, Steffany. "Juvenile Pelagic Fish Communities in the Mattaponi and Pamunkey Rivers, Virginia". W&M ScholarWorks, 1992. https://scholarworks.wm.edu/etd/1539617648.
Testo completo
43
Moore, Niels E. "Alternative Management Programs Within the Atlantic Sea Scallop Placopecten magellanicus Fishery: Property Rights, Transferable Quotas and Fishing Effort". W&M ScholarWorks, 1994. https://scholarworks.wm.edu/etd/1539617668.
Testo completo
44
Merchant, Orelia Eleta. "Shellfish Culture Area Designation Protocol Development". W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539617684.
Testo completo
45
Holton, Tracy D. "The Effects of Hook Type on the Hooking Mortality of Two Size Classes of Summer Flounder, Paralichthys dentatus". W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539617685.
Testo completo
46
Brooke, Sandra Dawn. "A Comparison of Natural and Laboratory Diets for the Culture of Marine Invertebrate Larvae American Oyster, Crassostrea virginica, Queen Conch, Strombus gigas, and Milk Conch, Strombus costatus". W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539617706.
Testo completo
47
Hager, Christian Harding. "Efficiency of Pound-Net Cull Panels: A Comparison of Size Selectivity and Relative Release for Weakfish (Cynoscion regalis) and Summer Flounder (Paralichthys dentatus)". W&M ScholarWorks, 2000. https://scholarworks.wm.edu/etd/1539617762.
Testo completo
48
Kilduff, David Patrick. "Cobia (Rachycentron canadum) Aquaculture: Captive Growth Rates and Product Quality Evaluation". W&M ScholarWorks, 2001. https://scholarworks.wm.edu/etd/1539617775.
Testo completo
49
Goff, Kevin D. "Ring Diameter and Closed Area Scallop Fisheries: The Performance of a Dredge with 4" Rings in the Atlantic Sea Scallop (Placopecten magellanicus) Fishery, in the Context of an Area Rotation Management Scheme". W&M ScholarWorks, 2002. https://scholarworks.wm.edu/etd/1539617790.
Testo completo
50
Lange, John David. "An Evaluation of Closed Area Boundaries of the Sea Scallop Stock in the Middle Atlantic Bight". W&M ScholarWorks, 2002. https://scholarworks.wm.edu/etd/1539617796.
Testo completo