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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Interpretation of equatorial current meter data as internal waves

Blumenthal, Martin Benno January 1987 (has links)
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, and Woods Hole Oceanographic Institution, 1987. / Bibliography: v. 2, leaves 376-381. / by Martin Benno Blumenthal. / Ph.D.
42

Identification of chemoautotrophic microorganisms from a diffuse flow hydrothermal vent at EPR 9° north using ¹³C DNA stable isotope probing and catalyzed activated reporter deposition-fluorescence in situ hybridization

Richberg, Kevin Patrick January 2010 (has links)
Thesis (S.M.)--Joint Program in Biological Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 47-54). / At deep-sea hydrothermal vents chemolithoautotrophic microbes mediate the transfer of geothermal chemical energy to higher trophic levels. To better understand these underlying processes and the organisms catalyzing them, this research used DNA Stable Isotope Probing (SIP) combined with Catalyzed Activated Reporter Deposition-Fluorescence in situ Hybridization (CARD-FISH) to identify the microorganisms chemoautotrophically supporting the food web at a diffuse flow hydrothermal vent. Both anaerobic and aerobic shipboard incubations containing various augmented electron donor and acceptor species showed that Epsilonproteobacteria were the dominant chemoautotrophs with greater than 70% of the cells counted within the first 24 hours. 13C DNA SIP identified unique organisms not previously characterized from low temperature diffuse flow venting: green sulfur bacteria (Chlorobi-like organisms) possibly utilizing photoautotrophy, aerobic Lutibacter litoralis-like organisms growing under anaerobic conditions, and Epsilonproteobacterial Thioreductor sp. at temperatures above maximum known tolerances. This research illustrates both the promise and pitfalls of the SIP technique applied to hydrothermal systems, concluding that timing of the incubation experiments is the critical step in eliminating undesired 13C labeling. These results set the stage for a more thorough future examination of diffuse flow microorganisms by presenting interesting questions that second generation experiments could be designed to answer. / by Kevin Patrick Richberg. / S.M.
43

Scale closure in upper ocean optical properties : from single particles to ocean color

Green, Rebecca E. (Rebecca Erin), 1972- January 2002 (has links)
Thesis (Ph.D.)--Joint Program in Biological Oceanography (Massachusetts Institute of Technology, Dept. of Biology, and the Woods Hole Oceanographic Institution), 2002. / Includes bibliographical references. / Predictions of chlorophyll concentration from satellite ocean color are an indicator of phytoplankton primary productivity, with implications for foodweb structure, fisheries, and the global carbon cycle. Current models describing the relationship between optical properties and chlorophyll do not account for much of the optical variability observed in natural waters, because of the presence of seawater constituents that do not covary with phytoplankton pigment concentration. In an attempt to better understand variability in these models, the contributions of seawater constituents to ocean optical properties were investigated. A combination of Mie theory and flow cytometry was used to determine the diameter, complex refractive index (n+n'i), and optical cross-sections of individual particles, based on a method developed in the laboratory using phytoplankton cultures. Individual particle measurements were used to interpret variability in concurrently measured bulk optical properties in New England continental shelf waters in two seasons. The summed contribution to scattering of individual particles in the size range of 0.1-50 Cpm accounted for approximately the entire scattering coefficient measured independently using bulk methods. In surface waters in both seasons, the large diameters and n' of eukaryotic phytoplankton caused them to be the main particle contributors to both absorption and scattering. Minerals were the main contributor to backscattering, bb, in the spring, whereas in the summer both minerals and detritus contributed to bb. Synechococcus and heterotrophic bacteria were less important optically, contributing <11% each to attenuation in either season. / (cont.) The role of seawater constituents in determining remote sensing reflectance, Rrs, was determined using radiative transfer theory. Seasonal differences in the spectral shape of Rrs were contributed to approximately equally by eukaryotic phytoplankton absorption, dissolved absorption, and non-phytoplankton bb. A higher inverse wavelength dependence of non-phytoplankton bb in the summer was caused by the contribution of small detritus, in contrast to larger minerals in the spring. Measurements of bb and Rrs were compared to values from bio-optical models based on chlorophyll concentration. Differences in measured and modeled bb and Rrs were caused by higher dissolved absorption and higher backscattering efficiencies and scattering by non-phytoplankton than were assumed by the model. / by Rebecca E. Green. / Ph.D.
44

Estimadores da resistência mecânica característica da madeira /

Pinheiro, Wendell, 1976- January 2011 (has links)
Orientador: Adriano Wagner Ballarin / Banca: José Raimundo de Souza Passos / Banca: Luiz Antonio Targa / Resumo: A qualificação da madeira para uso estrutural é feita com base na sua resistência característica à compressão paralela às fibras. A partir de valores individuais de resistência à compressão paralela de corpos de prova de uma amostra representativa do lote de madeira, a resistência característica é avaliada com estimador específico, proposto pela NBR 7190 (ABNT, 1997). Com o valor da resistência característica, o lote de madeira é classificado em classes de resistência (três classes distintas para madeiras de coníferas e quatro classes distintas para madeira de folhosas) que variam de 20 MPa a 60 MPa. Lotes de madeira com maior valor de resistência característica levam, na maioria das vezes, à otimização dos projetos estruturais. O objetivo principal deste trabalho foi avaliar a eficiência de vários estimadores da resistência característica de lotes de madeira de distintas procedências, gêneses e idades das árvores, com base em suas aplicações em amostras de diferentes tamanhos amostrais. Para o estudo foram utilizados lotes de resultados de resistência mecânica da madeira de diversos conjuntos de dados, abrangendo resistências à compressão paralela às fibras e resistências ao cisalhamento de madeiras nativas e de reflorestamento, coníferas e folhosas. Com uso do software estatístico SAS, para cada lote sortearam-se repetidamente amostras, variando-se os tamanhos amostrais e, a partir dos valores de resistência dos indivíduos de cada amostra foram calculadas as resistências características dos lotes. Tomando-se a resistência característica do lote (aqui assumido como população) como referencial, foi avaliada comparativamente a eficiência de cada estimador, com base no erro quadrático médio e no desvio da estimativa. 2 Os resultados mostraram que o estimador... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In Brazil, lumber classification for structural purposes is based on its characteristic strength in compression parallel to grain. From individual values of strength in compression parallel obtained from specimens of a sample, characteristic strength is evaluated with a particular estimator proposed by the standard NBR 7190 - Design of wood structures (ABNT, 1997) for general usage (all the mechanical properties). With this characteristic strength, lumber lot is classified into classes of strength (three different classes of coniferous woods and four different classes for hardwood) ranging from 20 MPa to 60 MPa. Lumber lots with higher characteristic strength leads, in general, to a design optimization. The main objective of this study was to evaluate the efficiency of several estimators of characteristic strength of lumber lots with distinct origin, genesis and ages, based on their application in samples with different size. Lots of results of strength in compression and in shear parallel to grain of conifers and hardwood from native and reforested plantation were used. Using SAS - Statistical Analysis System - specimens were randomly sampled from each lot - varying sample size from 6 to 42 specimens - from which the characteristic strength of the lot was calculated each time based on the estimators. Taking as referential the characteristic strength of the full lot (assumed as the population), comparative efficiency of the estimators were analyzed based on MSE (mean squared error) and deviation of the estimation. Results showed that the estimator proposed by NBR 7190(ABNT, 1997) was not the more efficient in all cases. For compression and shear parallel to grain, best estimations of characteristic strength were obtained with the estimator that uses lots central tendency and dispersion parameters in its formulation... (Complete abstract click electronic access below) / Mestre
45

When two become one: the cultural aspects of mergers : A case study of Fläkt Woods AB Sweden / När två blir en: Organisationskultur och dess effekt på en fusion : En fallstudie av Fläkt Woods AB Sverige

Hansson, Malin, Hansson, Matilda January 2006 (has links)
Denna kandidatuppsats söker att förklara vilken typ av effekter en fusion kan ha på en organisationskultur. För att genomföra en analys av fusionens effekter krävs att organisationskulturen sonderas och därmed kan användas som grund. Vi har valt att arbeta med Fläkt Woods eftersom de genomgick en fusion 2002 då det svensk-brittiska företaget föd-des. Arbetet fullföljdes genom en kvalitativ vinkel i form av en fallstudie. Sex djupgående intervjuer genomfördes med chefer och chefsassistenter på Fläkt Woods enheter i Enköping, Jönköping och Växjö. För att kunna blottlägga paradigmen, och därigenom skapa en förståelse för de underliggande värderingar som utgör en kultur, användes Cultural Web. Vi valde sedan att applicera Results of Cultural Integration (RCI)-modellen för att vidare förklara effekterna av fusionen. Som stöd för dessa modeller har vi använt oss av teorier om den kulturella integrationsprocessen och hur man, genom tre instrument, stödjer denna process. Resultatet av vår undersökning av paradigmen, som är representativt för organisationskulturen, pekar mot en atmosfär som omfattar positiva attityder, demokratiska beslutsförfarande, framtidsfokus och trygghet. Fusionen påverkade organisationskulturen genom att starta en pågående transformationsprocess. Detta är synligt då Enköping, Jönköping och Växjö för tillfället befinner sig i olika faser i denna process. Växjö utövar mycket samarbete med den brittiska delen av företaget och upplever därför kulturen som mer enhetlig än vad Enköping gör, där samverkan med Colchester är närmast obefintlig. Enheten i Jönköping har nått ett mellanliggande stadium eftersom de dels håller kvar sin egen kultur, men genom den ökande interaktionen med Woods utsätts för nya aspekter av organisationskulturen. Vi tror att Fläkt Woods organisationskultur kommer att fortsätta att förändras till de olika enheterna är mer synkroniserade. Förvandlingen mot en ny Fläkt Woods-kultur kommer inte att avstanna förrän Enköping och Jönköping har nått det stadium som Växjö befinner sig i för tillfället, och därmed börjar anamma den nya kulturen i en större utsträckning. Det ska dock noteras att eftersom ägarna till Fläkt Woods, Compass Holdings, inte har pressat högsta ledningen att medvetet arbeta med frågor som rör organisationskulturen så kommer integrationsprocessen att ta längre tid än om frågan hade varit av högre prioritet / This bachelor thesis aims to explain the area of how a merger can affect a corporate culture. In order to do this, the corporate culture needs to be explored to found a basis for the analysis of the merger effects. We have chosen to work with Fläkt Woodsas they took part of a merger in 2002 where the Swedish-British company was founded. The work was carried out with a qualitative approach, in the form of a case study. We performed six in depth interviews, with managers and managers’ assistants at Fläkt Woodssites in Enköping, Jönköping and Växjö. In order to uncover the paradigm, and thus understand the underlying assumptions of the culture, we used the Cultural Web. To further explain the effects of the merger, an application of the Results of Cultural Integration (RCI)-model was performed. To support the analysis we used theories on the cultural integration process as well as on how to support the integration process through three instruments. The results of our investigations of the cultural paradigm, which we hold as representative for the corporate culture, pointed toward an atmosphere which comprised positivism, democracy, focus on the future and safety. The merger affected the corporate culture by starting off an ongoing transformation process. This is visible as Växjö, Jönköping and Enköping are currently in different phases in the process. Växjö cooperate the most with the British unit situated in Colchester and thus experiences the culture as more unified than Enköping does where no interaction with England takes place. The site in Jönköping has reached an intermediate stage as they are partly clinging on to their own culture but at the same time, through the increasing interaction with Woods, are exposed to new aspects of the corporate culture. We believe that the corporate culture of Fläkt Woodswill continually change until the sites are more in tune with each other. The transformation towards a new Fläkt Woodsculture will not stop until Enköping and Jönköping have reached the stage that Växjö is currently in, and thus start to embrace the new culture to a larger extent. However, as the owner of Fläkt Woods, Compass Holdings, has not put any pressure on the top management to consciously work with the issues of corporate culture, the integration process will take longer than if the matter was of higher priority.
46

When two become one: the cultural aspects of mergers : A case study of Fläkt Woods AB Sweden / När två blir en: Organisationskultur och dess effekt på en fusion : En fallstudie av Fläkt Woods AB Sverige

Hansson, Malin, Hansson, Matilda January 2006 (has links)
<p>Denna kandidatuppsats söker att förklara vilken typ av effekter en fusion kan ha på en organisationskultur. För att genomföra en analys av fusionens effekter krävs att organisationskulturen sonderas och därmed kan användas som grund. Vi har valt att arbeta med Fläkt Woods eftersom de genomgick en fusion 2002 då det svensk-brittiska företaget föd-des.</p><p>Arbetet fullföljdes genom en kvalitativ vinkel i form av en fallstudie. Sex djupgående intervjuer genomfördes med chefer och chefsassistenter på Fläkt Woods enheter i Enköping, Jönköping och Växjö.</p><p>För att kunna blottlägga paradigmen, och därigenom skapa en förståelse för de underliggande värderingar som utgör en kultur, användes Cultural Web. Vi valde sedan att applicera Results of Cultural Integration (RCI)-modellen för att vidare förklara effekterna av fusionen. Som stöd för dessa modeller har vi använt oss av teorier om den kulturella integrationsprocessen och hur man, genom tre instrument, stödjer denna process.</p><p>Resultatet av vår undersökning av paradigmen, som är representativt för organisationskulturen, pekar mot en atmosfär som omfattar positiva attityder, demokratiska beslutsförfarande, framtidsfokus och trygghet.</p><p>Fusionen påverkade organisationskulturen genom att starta en pågående transformationsprocess. Detta är synligt då Enköping, Jönköping och Växjö för tillfället befinner sig i olika faser i denna process. Växjö utövar mycket samarbete med den brittiska delen av företaget och upplever därför kulturen som mer enhetlig än vad Enköping gör, där samverkan med Colchester är närmast obefintlig. Enheten i Jönköping har nått ett mellanliggande stadium eftersom de dels håller kvar sin egen kultur, men genom den ökande interaktionen med Woods utsätts för nya aspekter av organisationskulturen.</p><p>Vi tror att Fläkt Woods organisationskultur kommer att fortsätta att förändras till de olika enheterna är mer synkroniserade. Förvandlingen mot en ny Fläkt Woods-kultur kommer inte att avstanna förrän Enköping och Jönköping har nått det stadium som Växjö befinner sig i för tillfället, och därmed börjar anamma den nya kulturen i en större utsträckning. Det ska dock noteras att eftersom ägarna till Fläkt Woods, Compass Holdings, inte har pressat högsta ledningen att medvetet arbeta med frågor som rör organisationskulturen så kommer integrationsprocessen att ta längre tid än om frågan hade varit av högre prioritet</p> / <p>This bachelor thesis aims to explain the area of how a merger can affect a corporate culture. In order to do this, the corporate culture needs to be explored to found a basis for the analysis of the merger effects. We have chosen to work with Fläkt Woodsas they took part of a merger in 2002 where the Swedish-British company was founded.</p><p>The work was carried out with a qualitative approach, in the form of a case study. We performed six in depth interviews, with managers and managers’ assistants at Fläkt Woodssites in Enköping, Jönköping and Växjö.</p><p>In order to uncover the paradigm, and thus understand the underlying assumptions of the culture, we used the Cultural Web. To further explain the effects of the merger, an application of the Results of Cultural Integration (RCI)-model was performed. To support the analysis we used theories on the cultural integration process as well as on how to support the integration process through three instruments.</p><p>The results of our investigations of the cultural paradigm, which we hold as representative for the corporate culture, pointed toward an atmosphere which comprised positivism, democracy, focus on the future and safety.</p><p>The merger affected the corporate culture by starting off an ongoing transformation process. This is visible as Växjö, Jönköping and Enköping are currently in different phases in the process. Växjö cooperate the most with the British unit situated in Colchester and thus experiences the culture as more unified than Enköping does where no interaction with England takes place. The site in Jönköping has reached an intermediate stage as they are partly clinging on to their own culture but at the same time, through the increasing interaction with Woods, are exposed to new aspects of the corporate culture.</p><p>We believe that the corporate culture of Fläkt Woodswill continually change until the sites are more in tune with each other. The transformation towards a new Fläkt Woodsculture will not stop until Enköping and Jönköping have reached the stage that Växjö is currently in, and thus start to embrace the new culture to a larger extent. However, as the owner of Fläkt Woods, Compass Holdings, has not put any pressure on the top management to consciously work with the issues of corporate culture, the integration process will take longer than if the matter was of higher priority.</p>
47

International monetary relations between the United States, France, and West Germany in the 1970s

Rae, Michelle Frasher 30 September 2004 (has links)
The United States acted unilaterally to terminate the Bretton Woods monetary system in August 1971, and international exchange rate management went from a regime of fixed to floating parities, much to the displeasure of the membership of the European Community. The Nixon, Ford, and Carter administrations adopted policies that heavily benefited U.S. reform objectives and domestic economic goals, which frequently clashed with allied concerns, and damaged American monetary relations with France and West Germany. Yet, the inability of France and the Federal Republic of Germany to form cohesive economic and monetary policies throughout international negotiations or within the European Community (EC), allowed American desires to dictate the path and pace of European integration. France and Germany attempted, with limited success, to influence U.S. monetary policy through bilateral diplomacy during years of exchange rate fluctuations, dollar devaluations, oil shocks, and payments deficits. Finally, President Valery Giscard d'Estaing and Chancellor Helmut Schmidt created the European Monetary System (EMS) in 1979, reversing the trend of half-hearted attempts at European integration so relevant the decade before. The EMS detached the EC's currencies from the dollar's control, was compatible with the reformed international monetary system, advanced a more independent European monetary identity, and formed the base for future monetary integration. As a result, the EMS, as the birthplace of the Euro, the single European currency launched in 2002, may soon rival the dollar's position as the primary reserve currency. American monetary policies designed to improve the health of the dollar during the 1970s were a catalyst for European integration. However, as the European Union deepens its economic integration and the Euro grows in strength, it seems that U.S. policies created a regime and a currency that will challenge its dominant position in international monetary affairs.
48

Kertinių miško buveinių vaidmuo miško apsaugoje / Woodlands key habitat part in woods protection

Rugaitis, Gintautas 08 September 2009 (has links)
Santrauka Kertinių miško buveinių vaidmuo miško apsaugoje Gintautas Rugaitis Magistriniame darbe nagrinėjamas kertinių miško buveinių svarba miško ekosistemoms. Tyrimams buvo pasirinktas Kurtuvėnų regioninis parkas. Šiame parke yra išskirtos 195 kertinės miško buveinės. KMB inventorizacijoje detalus rūšių tyrimas nebuvo prioritetinis uždavinys. Pagrindinis šio darbo tikslas buvo ištirti vabalų fauną kertinėse miško buveinėse. Vabzdžiai yra viena iš labiausiai pažeidžiamų miško organizmų grandžių. Sprendžiant apie jų įvairovę, gausumą, gausumo pokyčius galima tiesiogiai įvertinti atskirų miško buveinių būklę. Visa tai sudaro sąlygas apibrėžti kokį vaidmenį KMB atlieka miško ekosistemose. Tirtose kertinėse buveinėse aptiktos 166 vabalų rūšys. 11 rūšių priklauso KMB vabalams, 3 iš jų specializuotos. Taip pat rastos dvi Lietuvos Raudonosios knygos rūšys. Apie 60% surinktų vabalų yra tipiški ksilobiontai. Tai yra gyvena arba vystosi medyje, medienos grybuose. Naudojant retų vabalų tyrimų rezultatus sudarytas potencialiai vertingų miško teritorijų žemėlapis. Darbe taip pat nagrinėjamos galimos kertinių miško buveinių apsaugos priemonės ir jų tvarkymo būdai. Atsižvelgiant į atskirų buveinių specifiškumą aptariamos tikėtinos vabalų rūšys, kurios galėtų vystytis tirtose buveinėse. / Summary Woodlands key habitat part in woods protection Gintautas Rugaitis In this scientific work is examining Woodlands key habitat part, importance woods ecosystems. For investigations Kurtuvėnai region park was selected. In this park are excluded 195 Woodlands key habitat. In WKH inventory varios species investigation was not priority object. The basic object in this work was investigation beetle fauna in WKH. Insects are one of the most violate wood organism links. If saluting about they diversity, abundance, abundances changes it's possible to appraise separated woods habitat status. This makes conditions defmition, what part WKH is making wood ecosystems. In examined Woodlands key habitat was discovered 166 beetle species. 11 species are belong to WKH beetle, 3 of them are specialized. Also was found 2 of Lithuania Red book species. About 60% collected insects are typical saproxylic beetle. It means that they live in wood, wood fungus. Using rear beetle researehes results was made potential valuable wood territory map. In work also examining possible woodlands key habitat security measure and they regulations means. Consider in separated habitat specific is discussing possible insects species, which cud develop in examined habitat.
49

Gražutės regioninio parko dendroflora, vyraujantys medynai ir jų išteklių gamtosauginiai aspektai / Dendroflora of Grazute Regional Park, prevailing woods and ecological aspects of their resources

Leleckienė, Jūratė 29 June 2009 (has links)
Gražutės regioninis parkas yra šiaurrytinėje Lietuvos dalyje – Zarasų ir Ignalinos savivaldybių teritorijose. Regioninio parko plotas pagal patikslintas (naudojant skaitmenines technologijas) ribas yra 29 471 ha. Šio darbo tikslas - ištirti Gražutės regioninio parko savaiminės dendrofloros botaninę įvairovę, sudaryti rūšių sistematinį spektrą, pateikti jų chorologinį įvertinimą, išsiaiškinti vyraujančius medynus ir įvertinti jų būklę, aprašyti retąsias rūšis bei gamtos paminklais paskelbtus medžius, apžvelgti kertines miško buveines ir Natura 2000 teritorijas, genetinius ir sėklinius draustinius, etaloninius medynus, supažindinti su pažintiniais takais. Tyrimų metu nustatyta, kad Gražutės regioniniame parke auga 70 savaiminių sumedėjusių augalų rūšių iš 94, žinomų Lietuvoje (Navasaitis ir kt., 2003), o tai sudaro 74 procentus visų Lietuvoje augančių savaiminės dendrofloros rūšių. Iš jų yra 4 pušūnų ( Pinophyta) skyriaus augalų rūšys, priklausančios 4 gentims ir 3 šeimoms (6 proc. nuo visų parke augančių savaiminių rūšių), kitos – magnolijūnų (Magnoliophyta) skyriaus augalų rūšys, priklausančios 36 gentims ir 20 šeimų. Atlikus parko savaiminių sumedėjusių augalų rūšių chorologinio spektro analizę, nustatyta, kad zoniniu požiūriu vyrauja boreotemperatinės rūšys (31), regioniniu – europinės rūšys (24), okeaniniu – euriokeaninės rūšys (28). Biogeocenotiniu požiūriu miškai skirstomi į 4 miško tipų kompleksus, iš kurių šilai GRP užima 8841,3 ha (55,0%) medynų ploto, girios... [toliau žr. visą tekstą] / Gražutė Regional Park is located in the northeast of Lithuania in the territories of Zarasai and Ignalina municipalities. The area of the regional park according to the revised borders (calculated using digital technologies) makes 29 471 ha. The aim of this thesis is to examine the botanical diversity of spontaneous dendroflora of Gražutė Regional Park, design the systematic spectrum of the species, present their chorologic evaluation, identify the prevailing woods and assess their condition, describe the rare species and trees that have been declared as the monuments of nature, make an overview of foundation forest seats and Natura 2000 territories, genetic and seminal reserves, standard woods, introduce to cognitive walkways. The research allowed finding out that Gražutė Regional Park hosts 70 species of spontaneous woody plants out of 94 known in Lithuania (Navasaitis and others, 2003) what makes 74 percent of all the species of spontaneous dendroflora growing in Lithuania. Out of them, there are 4 species of Pinophyta division belonging to 4 genuses and 3 families (6 percent of all the spontaneous species growing in the park), among others there are species of Magnoliophyta division belonging to 36 genuses and 20 families. After the chorologic spectrum analysis of the species of spontaneous woody plants growing in the park has been carried out, it has been found out in the areal terms that boreotemperate species are prevailing (31), in regional terms – European... [to full text]
50

A diatom-based paleolimnological investigation of historical water-quality and ecological changes in the Lake of the Woods, Ontario

Hyatt, Crystal 28 May 2010 (has links)
A two-part paleolimnological study was conducted to examine changes in historical and modern water-quality in Lake of the Woods (LoW) in response to multiple stressors, such as climate change and shoreline residential development. Changes in diatom assemblages were analyzed in the modern and pre-industrial sediment intervals of 17 study sites, and in high-resolution 210Pb-dated sedimentary records from three northwestern bays (Clearwater, Poplar, and White Partridge bays). Patterns in diatom assemblage changes revealed pronounced and synchronous shifts over the last ca. 150 years. The most notable shift in the diatom community structure (~1970 AD) was characterized by an overall shift towards a higher relative abundance of small, centric Cyclotella taxa and planktonic, pennate diatoms (e.g., Asterionella formosa, Fragilaria crotonensis), and a corresponding lower relative abundance of heavily silicified Aulacoseira taxa and small benthic Fragilaria taxa and Achnanthes taxa. Lakewater total phosphorus (TP) concentrations were inferred from sedimentary diatom assemblages. DI-TP reconstructions revealed either no change or a decline in DI-TP since pre-industrial (pre-1850) times at majority (88%) of the top-bottom study sites, and no distinct directional change over the past ca. 150 years at the northwestern bays. Therefore, we concluded that TP was not an important driver of the floristic changes we observed. Chl-a trends indicate that primary production increased during the last ca. 100 years, likely tracking increases in microbial blooms. Changes in diatom assemblage composition and primary productivity have occurred during a period of substantial warming for this region of northwestern Ontario. Strong correlations (r >0.50, p<0.005) between diatom compositional changes, chl-a trends, and local air temperature records and lake-ice phenology suggest that climate-induced changes in lakewater properties may have been key factors driving the observed changes. From these data, we conclude that climate warming, rather than changing shoreline development and TP changes, has had the most pronounced effect on algal communities in the LoW. Estimates of pre-impact lake trophic status can aid in setting realistic mitigation targets for lakes impacted by multiple stressors. Therefore, paleolimnological studies comparing pre- and post-disturbance algal assemblages, such as the investigations we have conducted, are of interest from a lake management perspective. / Thesis (Master, Biology) -- Queen's University, 2010-05-28 13:38:59.472

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