Increased groundwater usage, rainfall decline and activities such as mining have resulted in the acidification of certain wetlands in the south-west of Western Australia. This study investigated the influence of pH, the factor most commonly associated with acidification, on the invertebrate and diatom community structure of 20 wetlands in the south-west region of Western Australia. Few studies in Western Australia have investigated both biotic groups, particularly in relation to pH. Consequently, this study examined the comparative sensitivity of the two biotic groups to pH in order to identify the most effective biotic tool for assessing the ecological impacts of pH decrease. The wetlands included in this study displayed a wide range of pH from acidic (pH < 6.5) to alkaline (pH > 7.5). Other environmental parameters were also variable. Separation of the wetlands into three pH groups; Group 1 – acidic, Group 2 – circumneutral and Group 3 – alkaline, demonstrated that the acidic Group 1 wetlands generally had higher electrical conductivity than the remaining groups. This was probably due to the association of many Group 1 sites with mining and acid sulphate soils. Seasonal trends in environmental variables across the three pH groups were mostly unclear although some trends were evident within the individual pH groups. The study showed that invertebrate community structure differed in response to pH. However, the results also demonstrated that invertebrate distribution patterns were influenced by other factors. / Potential indicator species identified from the study included Macrothrix indistincta and Tanytarsus fuscithorax/semibarbitarsus which were abundant in acidic waters and Alona quadrangularis which was common in circumneutral sites. Taxa such as Calamoecia tasmanica subattenuata were common over a wider range of pH (acidic to circumneutral) but may still have potential to act as indicators of pH decline. Diatom community structure was also shown to be influenced by pH, with the variable identified as a major determinant of diatom distribution patterns. Nitzschia paleaeformis and Navicula aff. cari were generally recorded from acidic wetlands and are potentially useful as indicators of low pH conditions. Brachysira brebissonii and Frustulia magaliesmontana were also identified as species with the potential to indicate pH decline. In contrast, taxa including Gomphonema parvulum, Staurosira construens var. venter and Nitzschia palea were generally associated with moderate to high pH levels. A comparative study of the two biotic groups using multivariate analyses revealed that diatoms were more sensitive to pH than invertebrates. Further investigation with a larger number of environmental variables would be necessary to ascertain the other factors primarily influencing invertebrate community structure. Nonetheless, the findings imply that diatoms and invertebrates differ in their responsiveness to various environmental factors and may provide complementary information on the integrity of a system. Multivariate analyses on an expanded data-set of 40 sites found that pH accounted for the greatest amount of variation in the data and was conducive to the development of a diatom-based pH inference model. / The strongest model was produced using weighted averaging (WA) with classical deshrinking. While the model displayed a high correlation coefficient, the prediction error was also relatively high, probably as a result of the comparatively small and heterogeneous data-set. Incorporation of the data into a larger training set would be likely to improve the predictive ability. Applications for the model include pH reconstructions or use in monitoring programs. The current study has shown that pH is an important variable influencing both invertebrate and diatom community structure in wetlands in the south-west of Western Australia. However, the greater sensitivity of diatoms to pH suggests that they would be the most effective tool for the biological monitoring of pH in wetlands threatened or impacted by acidification. An integrated monitoring program including both diatoms and invertebrates may provide additional information on the impacts of pH decline and the overall integrity of the systems and should be investigated further.

This thesis investigates how variations in the oxygen isotopic composition of lake waters in northern Fennoscandia are recorded in lake sediment archives, especially diatoms, and how these variations can be used to infer past changes in climate and atmospheric circulation. Results from analyses of the oxygen isotopic composition of lake water samples (δ18Olakew) collected between 2001 and 2006 show that δ18O of northern Fennoscandian lakes is mainly controlled by the isotopic composition of the precipitation (δ18Op). Changes in local δ18Op depend on variations in ambient air temperature and changes in atmospheric circulation that lead to changes in moisture source, vapour transport efficiency, or winter to summer precipitation distribution. This study demonstrates that the amount of isotopic variation in lake water δ18O is determined by a combination of the original δ18Olakew, the amount and timing of the snowmelt, the amount of seasonally specific precipitation and groundwater, any evaporation effects, and lake water residence time. The fact that the same isotope shifts have been detected in various δ18Olakew proxies, derived from hydrologically different lakes, suggests that these records reflect regional atmospheric circulation changes. The results indicate that diatom biogenic silica isotope (δ18Odiatom) records can provide important information about changes in atmospheric circulation that can help explain temperature and precipitation changes during the Holocene. The reconstructed long-term Holocene decreasing δ18Op trend was likely forced by a shift from strong zonal westerly airflow (relatively high δ18Op) in the early Holocene to a more meridional flow pattern (relatively low δ18Op). The large δ18Olakew depletion recorded in the δ18O records around ca. 500 cal yr BP (AD 1450) may be due to a shift to more intense meridional airflow over northern Fennoscandia resulting in an increasing proportion of winter precipitation from the north or southeast. This climate shift probably marks the onset of the so-called Little Ice Age in this region. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 2: Submitted. Paper 5: In progress.

Domoic acid (DA), a potent neurotoxin that has the potential to cause amnesic shellfish poisoning (ASP), is produced by members of the marine diatom genus Pseudo-nitzschia. Outbreaks of ASP in humans and of DA poisoning in birds and marine mammals have been reported across the United States and Canada since the late 1980's. Pseudo-nitzschia species can be extremely abundant in Florida waters, with densities often exceeding 106 cells/L, and sometimes exceeding 107 cells/L. Based on preliminary data, it is evident that at least nine species of Pseudo-nitzschia are found in Florida coastal waters. At least six of these species are known to produce DA in other parts of the world, and some are morphologically identical to some of the major toxin-producing species in Californian and Canadian waters. Despite the strong presence of Pseudo-nitzschia, there has never been a report of ASP or a DA-related animal mortality event from Florida. Data collected from 2004 to 2011 show maximum Pseudo-nitzschia abundances exceeded 4 x 107 cells/L. Six species of Pseudo-nitzschia were identified from central west and southwest Florida waters via light and electron microscopy. This is the first report of P. micropora from the Gulf of Mexico. Additionally P. calliantha, P. cuspidata, and P. pungens were identified as producers of DA in Florida coastal waters; although cell quotas of DA were low. Low levels of DA were detected in about one third of the water samples analyzed and DA concentrations measured in the majority of shellfish from the study area were at least an order of magnitude below the regulatory limit of 20 µg/g, suggesting that Pseudo-nitzschia currently poses little threat to human health in Florida. However, DA production in Pseudo-nitzschia species has been shown to be variable and dependent on nutrient conditions, indicating that the potential for DA-related events to occur in Florida warrants further investigation.

Les éléments génétiques transposables (ET) sont des séquences d’ADN capables de se déplacer dans tous lesgénomes sous certaines conditions. Les ET ont des structures et des modes de transposition qui lesdifférencient en plusieurs groupes. Les éléments de la famille mariner sont ubiquistes ; lorsqu’ils sont actifs, ilsproduisent une transposase qui coupe l’élément et l’insère dans un autre locus. Des fragments d’éléments detype mariner (MLE) ont été précédemment identifiés chez la diatomée marine Amphora acutiuscula et ils semblaientactifs en condition de stress thermiques. Les diatomées sont caractérisées par une paroi siliceuse ornementée et,dans le milieu marin, elles jouent un rôle primordial dans les chaînes alimentaires.Dans le présent travail, par des méthodes de biologie moléculaire et de bioinformatique, nous avons recherché et caractérisé des MLE complets, et précisé leur activité en conditions de chocs thermiques et métalliques (cuivre et zinc). L’analyse des séquences amplifiées a mis en évidence la présence de MLE particuliers chez cette diatomée qui code une transposase ayant une triade catalytique DD43D jamais décrite jusqu’à présent.L’analyse phylogénétique place les MLE de diatomées dans une sousfamille différente mais proche de celle desMLE de plantes. Parmi les nombreuses copies de MLEprésentes dans le génome d’A. acutiuscula, certaines sont exprimées lorsque la diatomée est placée pendant 2 à 5 heures à unetempérature inférieure à sa température de culture. Par contre, l’expression des MLE n’a pas été mise en évidence chez cette espèce soumise aux stress métalliques appliqués. / Transposable elements (TE) are DNA sequences able to move in all genomes depending on conditions. TE have different structures and transposition mechanisms. Tc1-mariner elements are ubiquist ; when they are active, they produce a transposase which cuts and inserts the element into another locus. Fragments of mariner-like elements (MLE) hadpreviously been identified in the marine diatom Amphora acutiuscula and they seemed active under thermal stress. Diatoms are characterized by a siliceous ornamented cell wall and, in the ocean, they play a major role in trophic networks.In this work, with biomolecular and bioinformatic methods, we have searched for and characterized full length MLE, and precised their activity under thermal and metal (copper and zinc) stresses. The analyse of the DNA sequences obtained highlighted that MLE in diatoms are particular and that they encode a transposase which has a DD43D catalytic triad neverso far depicted. The phylogenetic analyse arranged diatom MLE in a subfamily different and close to that of plant MLE. Among the numerous MLE copies present in the genome of A.acutiuscula, some were expressed when the microalga was put at a lower temperature than the culture temperature for 2 to 5 hours. Conversely, metal stresses we applied did notinduce MLE expression in this species.

The subject of this thesis is selected parameters cement mortars with partial replacement of Portland cement diatomaceous earth. This work provides information on the basic properties of diatomaceous earth and its deposits with a focus on deposit in Borovany. From the properties is very important pozzolanic activity due to the high content of amorphous silica of this soil. The main use of diatomaceous earth is in the area filtration and is used widely as a nutritional supplement. In the building industry, diatomite can be applied as an admixture to mortar and concrete, where it can, with its abilities, improve some physical mechanical properties. In the experimental part was diatomaceous earth, in its raw and calcined form, tested as admixture for cement pastes and mortars. The main criterion for evaluating these composites was bulk density, flexural and compressive strength. It was also investigated mineralogical composition, microstructure, freeze–thaw resistance and sulfate resistance.

The silica-based cell walls of diatoms are outstanding examples of nature’s capability to synthesize complex porous structures with genetically controlled patterns from the nanometer scale to the range of hundreds of micrometers. Formation of the cell wall building blocks (valves and girdle bands) occurs in membrane-bound compartments, termed silica deposition vesicles (SDVs), which are unique organelles in silica-forming protists. Isolation of the SDVs has not yet been achieved, which has severely hampered the efforts to understand the mechanisms of biological silica morphogenesis. The present thesis aimed to address this shortcoming. The foundation was the development of an improved cell cycle synchronization and a fluorescence labeling method for the model diatom Thalassiosira pseudonana that enabled rapid identification of valve SDVs in a cell lysate. Correlative fluorescence and electron microscopy allowed visualizing the development of valve silica with unprecedented spatio-temporal resolution. Elemental analysis and demineralization of immature valves provided the first direct chemical evidence that silica morphogenesis is an interplay of inorganic and organic molecules inside the valve SDVs. Cryo TEM imaging of valve SDVs indicated the formation of organic patterns that precede silica depostion. From these observations, an organic biomolecule dependent, liquid-liquid phase separation based model for pore formation in the diatom T. pseudonana was proposed. The second part of this thesis was focused on the enrichment of valve SDVs from T. pseudonana and the subsequent proteomics based identification of more than 40 potential valve SDV proteins. Among these, three diatom-specific proteins contained conserved protein protein interaction domains (ankyrin-repeats) and were surprisingly predicted to be located in the cytoplasm. The fluorescent tagging of the three proteins (termed dANK1-3) confirmed their association with the valve SDVs. When the respective dank genes were knocked out by CRISPR/Cas9, the valves displayed permanent anomalies in the quantity and the pattern of ~22 nm sized pores. Double knockout mutants lacking both dank1 and dank3 were almost completely devoid of pores. The analysis of valve morphogenesis in the single and double knockout mutants revealed phenotypic changes that were consistent with the liquid-liquid phase separation based model for pore pattern formation in diatom biosilica. The work of this thesis has provided for the first time direct access to valve SDVs, which has opened entirely new possibilities for studying the composition, properties, and working mechanism of an organelle that forms a complex shaped mineral.

Detta projekt fokuserar på att undersöka dynamiken hos partiklar inom en-partikelsystem samt sammankopplade partiklar i tvåpartikelsystem genom tillämpning av numeriska metoder. Tvåpartikelsystemet som studeras är NaI-molekylen och dess dynamik, där beteendet undersöks efter systemet utsatts för en femtosekundslaserpuls. För att uppnå projektets mål utformas numeriska metoder med hjälp av finita differenser och Arnoldis tidsintegrationsalgoritm samt Runge-Kutta 4. Metoderna utvärderas med hjälp av den kvantharmoniska oscillatorn som har en analytisk lösning. Konvergensen för de olika ordningarnas finita differenser testas på den tidsoberoende Schrödingerekvationen för systemet. Arnoldi och RK 4 utvärderas på den tidsberoende Schrödingerekvationen. Baserat på dessa resultat görs en tidkonvergens- och tidseffektivitetsanalys för tidsstegningssmetoderna. Studien visar på att Arnoldi-metoden uppvisar ett större stabilitetsområde, vidare visas det att RK4 är den mindre beräkningstunga metoden för den kvantharmoniska oscillatorn. Resultatet av förstudien visar att finita differenser av åttonde ordningen ger den mest noggranna numeriska approximationen, utöver det görs avvägningen att tidsstegningsmetoderna kräver ytterligare undersökning. Därefter tillämpas den numeriska metoden för att analysera dynamiken hos NaI-molekylen. Tidseffektivitetsstudien för denna del av projektet visar att Arnoldi med 10 iterationer är mest passande för resten av projektet på grund av dess stabilitetsområde samt fördelaktiga hantering av större mer komplexa Hamiltonianer. Simuleringarna av tvåpartikelsystemet visar att när laserns våglängd varierar, varierar den energimängd som tillförs till systemet. Detta kan ses i att populationsnivån på den övre potentialytan är högre för kortare våglängder, och även i att perioden för oscillationerna är längre. När varaktigheten hos laserpulsen ökas observeras en större population på den högre energinivån. Detta eftersom en lång pulslängd leder till en minskad variation i population av energinivåerna på de exciterade vågfunktionerna. För laserpulser vars våglängd korresponderar med rätt energi för excitation leder det till en högre population av exciterade vågfunktioner. Projektets resultat bidrar till en djupare grundläggande förståelse av hur olika parametrar hos femtosekundslasrar påverkar kemiska reaktioner och dynamik på submolekylär nivå.

Paleoclimatic archives, such as lake sediments, extend our understanding of terrestrial and aquatic ecosystem dynamics in relation to climate variability beyond the period covered by instrumental data. In this context, annually laminated (i.e. varved) lake sediments are particularly valuable, as they offer high temporal resolution and undisturbed sediment. However, in order to extract reliable climate information from lake sediments, a careful calibration with the processes controlling the sediment formation is essential. This thesis combines limnological and paleolimnological data from a varved, boreal lake in northern Sweden (Nylandssjön, Nordingrå) collected over different time scales. The main aim of the thesis is to gain a more refined insight into which processes are reflected in the sedimentary diatom assemblage. More specifically, sequential sediment trap records were coupled with physical, chemical and biological lake monitoring and environmental data for comparison and validation with the varved sediment record. The main result of the thesis is that timing, succession and inter-annual variability of key limnological and environmental processes (e.g. ice-cover duration, lake over-turn or catchment run-off) are of major importance for the sedimentary diatom assemblage formation. Continuous monitoring of physico-chemical parameters over three consecutive years identified varying winter air temperature as a major factor influencing in-lake processes and hence the diatom record. Timing of lake over-turn and catchment run-off seemed to be the driver for monospecific diatom blooms, which are reflected in the annual sediment signal. The integrated annual diatom signal in the sediment was dominated by spring or autumn blooms, resulting either from a Cyclotella glomerata dominated spring bloom after relatively warm winter conditions, or a Asterionella formosa dominated autumn bloom after relatively cold winter conditions. The analysis of the diatom stratigraphy in the varved sediment over several decades corroborated the importance of climatic variables (late winter air temperature and NAO), even though the variables with the most predictive power for variance in the diatom data were associated with sediment composition (C, N and sedimentation rate) and pollution (Pb and Cu). Overall, the analysis of the drivers of inter-annual and decadal diatom assemblage fluctuations emphasizes the importance of winter air temperature, indicating that weather extremes may be disproportionately represented in annual sediment records in contrast to nutrient concentrations or sedimentation rate.

Orientador: Denise de Campos Bicudo / Resumo: Este estudo baseou-se em um banco de dados limnológicos e biológicos (diatomáceas de sedimento superficial e da coluna da água) de 33 reservatórios com gradiente trófico (ultraoligotrófico a hipereutrófico) distribuídos na região sudeste do Estado de São Paulo. Visou, como primeira etapa, calcular os ótimos e as tolerâncias ecológicas (etapa de regressão) das espécies de diatomáceas com a finalidade de propor um índice de diatomáceas para avaliar o estado trófico de represas, bem como um modelo de função de transferência diatomácea-fósforo (etapa de calibração) para inferir níveis pretéritos de fósforo da água. Além disso, visou avaliar o efeito da eutrofização sobre a homogeneização taxonômica e funcional das comunidades de diatomáceas. As amostras do sedimento superficial (n = 113) e do plâncton (verão e inverno, n = 226) foram obtidas entre 2009 e 2014. O método da média ponderada (WA) foi utilizado para a etapa de regressão (ótimo e tolerância das espécies), e modelos de regressão clássica e inversa foram testados para a etapa de calibração para a proposição do índice trófico de diatomáceas e para o modelo de função de transferência diatomácea-fósforo. Foram calculados os ótimos e as tolerâncias de fósforo total para 58 (sedimento superficial) e 53 (plâncton) espécies de diatomáceas. O modelo proposto com base nas diatomáceas do sedimento superficial apresentou melhor habilidade (r2 0.71, p<0.001, RMSE 49.43 μg L-1) do que as planctônicas para proposição do índice de esta... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study was based on a limnological and biological database (surface sediment and water column diatoms) of 33 reservoirs with trophic gradient (ultraoligo- to hyperereutrophic) distributed in the southeastern region of São Paulo State. The first aim was to calculate the optimum and ecological tolerances (regression stage) of diatom species in order to propose a diatom index to evaluate the trophic state of reservoirs, as well as a model of diatom-phosphorus transfer function (calibration step) to infer past levels of water phosphorus. In addition, it aimed to evaluate the effect of eutrophication on the taxonomic and functional homogenization of diatom communities. Surface sediment (n = 113) and plankton (summer and winter, n = 226) samples were obtained between 2009 and 2014. The weighted average (WA) method was used for the regression step (optimal and species tolerance), and classical and inverse regression models were tested for the calibration step for the proposition of the trophic index of diatoms and for the diatom-phosphorus transfer function model. Optimum and tolerances for total phosphorus were calculated for 58 (surface sediment) and 53 (plankton) diatom species. The model based on the surface sediment diatoms presented better ability (r2 0.71, p<0.001, RMSE 49.43 μg L-1) than phytoplankton diatom to propose the trophic diatom index of reservoirs (TDIR). The transfer function model showed high predictive ability (r2 0.80) and was based on 63 diatom species (su... (Complete abstract click electronic access below) / Doutor

O registro de depósitos quaternários tem aumentado em áreas costeiras da região Amazônica. No entanto, estudos detalhados são ainda necessários visando interpretar seus ambientes de deposição, bem como reconstituir sua evolução ao longo do Quaternário. Em particular, faltam informações sobre a reconstituição das variações do nível relativo do mar ao longo da margem equatorial brasileira de modo a possibilitar a inclusão dessa área em discussões de interesse regional e global enfocando clima, tectônica e eustasia. O presente trabalho representa um esforço de integração de vários tipos de dados, i.e., sedimentologia, estratigrafia, palinologia, diatomácea, datação 14C, \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' e C/N, objetivando reconstituir a evolução de paisagens no leste da Ilha do Marajó durante o final do Quaternário. Aspectos ligados a paleoambientes de sedimentação, padrões de vegetação, flutuações climáticas e variação do nível do mar serão abordados. Um total de 98 amostras de sedimentos argilosos e arenosos foi obtido de 85 m de testemunhos coletados com a sonda à percusão Robotic Key System (RKS). Estes testemunhos derivam de cinco poços (TSM4, TSM8, TSM10, TSM11 e TSM12) variando entre 10 e 24 m de profundidade, que foram distribuídos em um transecto proximal-distal correspondente a uma paleomorfologia em funil relacionada a um paleoestuário. As idades registradas variam entre 42.580 (±1430) anos A.P. e 3.184 (±37) anos A.P. Análises de fácies indicaram depósitos de areias grossas a finas, com estratificações plano-paralelas ou cruzadas, e argilas, maciças ou laminadas, intercaladas por camadas heterolíticas. Estas sucessões apresentam padrão granocrescente e/ou granodecrescente ascendente. Valores de \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' e C/N sugerem matéria orgânica oriunda de fontes diversas, com contribuição de plantas terrestres (principalmente plantas \'C IND.3\'), bem como fitoplâncton marinho e de água doce, como tipicamente esperado em estuários. A combinação de dados isotópicos, C/N e associações de fácies, permitiu identificar ambientes deposicionais correspondentes a canal fluvial, planície de inundação, canal e planície de maré, bacia central, delta de maré, complexo barreira/inlet e lago. A análise palinológica apresentou mistura de táxons típicos de floresta, de vegetação aberta e de mangue. Em geral, não se detectou mudanças drásticas nos padrões de vegetação no leste da Ilha de Marajó nos últimos 40.000 anos. A assembléia polínica foi melhor representada nos testemunhos dos poços TSM8 e TSM4. Neste último, as oito amostras basais (i.e., MR248 a MR258) registraram tipos arbóreos, como Alchornea, Euphorbiaceae, Euterpe, Malpighiaceae e Moraceae/Urticaceae. Na vegetação de mangue, Rhizophora constituiu o gênero mais comum, enquanto Poacea e Cyperaceae foram os mais freqüentes entre os táxons de ervas. A proporção entre pólen de floresta e de ervas mostrou-se constante em todas as zonas inseridas no Pleistoceno Tardio. Porém, aumento significativo de tipos herbáceos, com espécies pioneiras representadas por Alchornea e Moraceae/Urticaceae, foi registrado a partir de 6.790 (±60) anos A.P. Portanto, esta é a idade considerada para o estabelecimento de vegetação aberta do leste da Ilha de Marajó. Análises de diatomáceas dos testemunhos TSM8, TSM10 e TSM11, onde não houve registro polínico, foram consistentes com o valores isotópicos e de C/N, indicando intervalos com maior contribuição de matéria orgânica derivada de fitoplâncton marinho. Diatomáceas identificadas nestes testemunhos são, em grande parte, espécies e gêneros marinhos, como Actinoptychus splendens, Paralia sulcata, Coscinodiscus radiatus, Coscinodiscus sp e Thalassiosira sp. Táxons continentais como Actinella sp1, Aulacoseira, Eunotia zygodon, Desmogonium e Pinnularia foram registrados em uma única amostra no topo do testemunho TSM8. Informações faciológicas, juntamente com dados isotópicos, elementares, \'ANTPOT.14 C\', palinológicos e de diatomáceas, são consistentes com a existência de paleoestuário com domínio de onda no Pleistoceno Tardio e Holoceno no nordeste da Ilha do Marajó, previamente ao estabelecimento do lago Arari. As fases iniciais propostas para a interrupção do influxo fluvial para o paleoestuário Arari coincidem com a formação de vegetação aberta na ilha e a conseqüente diminuição das áreas de mangue no Holoceno médio. O efeito da tectônica regional parece ter sido de grande contribuição nas mudanças da paisagem do Marajó durante o Pleistoceno e Holoceno. Divergência do nível relativo do mar proposto para a Ilha do Marajó em relação ao padrão global, combinado com o aumento de registro de atividade tectônica no Pleistoceno Tardio e Holoceno, levaram à hipótese de que eventos transgressivos poderiam ter sido devidos à subsidência tectônica, e não à eustasia. A transgressão registrada antes de 29.000 anos A.P. ocorreu simultaneamente à forte tendência de queda eustástica após o Último Máximo Interglacial. Além disto, a transgressão holocênica no Marajó é registrada entre 9.000 e 5.000 anos A.P., portanto tendo início antes do pico transgressivo global do Holoceno médio. Durante este período de ascensão eustática, o nível relativo do mar na Ilha de Marajó começou a estabilizar, processo este que culminou com a significativa progradação da costa no final deste período. Da mesma forma, é improvável que a abertura da vegetação, com aumento significativo em espécies herbáceas, registrada a partir do Holoceno médio tenha efeito climático, uma vez que ela ocorreu simultaneamente à mudança de clima relativamente mais árido para relativamente mais úmido. A hipótese mais provável é que vegetação aberta tenha se estabelecido no leste da Ilha de Marajó em função de mudança hidrológicas, talvez promovida pela subsidência tectônica e subseqüente estabilização, culminada com a recente progradação da linha de costa. / The record of Quaternary deposits has increased in coastal areas of the Amazon region. However, detailed studies are still needed aiming to interpret their depositional environments, as well as reconstruct their evolution throughout the Quaternary. In particular, there is a lack of information about the reconstruction of relative sea level along the Brazilian equatorial margin to enable the inclusion of this area in discussions of regional and global interest focusing climate, tectonics and eustasy. The present work represents an effort to integrate vários types of data, i.e., sedimentology, stratigraphy, palinology, diatoms, \'ANTPOT.14 C\' dating, \'ANTPOT.13 C\', \'delta\' \'ANTPOT.15 N\' and C/N, aiming to reconstruct landscape evolution in eastern Marajó Island during the late Quaternary. Aspects related to sedimentary paleoenvironments, vegetation patterns, climate fluctuations and relative sea level changes will be approached. A total of 98 samples of muddy and sandy sediments was obtained from 85 m of cores collected with a percusion Robotic Key System (RKS). These cores derive from five drills (TSM12, TSM11, TSM10, TSM8 and TSM4) that reached depths ranging from 10 to 24 m, which were distributed in a proximal-distal transect corresponding to a funnel paleomorphology related to a paleoestuary. Reported ages range from 42, 580 ± (1430) \'ANTPOT.14 C\' yr B.P and 3,184 ± (37) \'ANTPOT.14 C\' yr B.P. Facies analysis showed parallel laminated or cross stratified, fine- to coarse-grained sands, massive or laminated muds and heterolithic deposits. These deposits are often arranged into coarsening and fining upward cycles. Values of \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' and C/N suggest organic matter from several sources, with contributions from terrestrial plants (mainly \'C IND.3\' plants), as well as freshwater and marine phytoplankton, as typically expected in estuaries. Combination of isotope data, C/N and facies associations led to identify depositional settings corresponding to fluvial channel, floodplain, tidal channel/tidal flat, central basin, tidal delta, inlet/barrier complex and lagoon. Pollen analysis showed a mixture of taxa typical of forest, open vegetation and mangrove. In general, drastic changes in vegetation patterns were not detected in eastern Marajó Island in the last 40,000 years. Pollen assemblages were better represented in cores TSM8 and TSM4. In the latter, the eight basal samples (i.e., MR248 to MR258) recorded arboreal types sucha as Alchornea, Euphorbiaceae, Euterpe, Malpighiaceae e Moraceae/Urticaceae. Among mangrove vegetation, Rhizophora constitutes the most common genera, while Poacea and Cyperacea were the most frequent among the herb taxa. The proportion between forest and herb pollen was constant in all zones inserted in the Late Pleistocene. However, significant increase of herbaceous pollen types, with pioneer species represented by Alchornea and Moraceae/Urticaceae, were recorded from 6,790 (±60) \'ANTPOT.14 C\' yr B.P. Thus, this is the age considered for the establishment of the open vegetation of eastern Marajó Island. Diatom analyses of the cores TSM8, TSM10 e TSM11, which did not record pollen, were consistent with the isotope and C/N values, indicating intervals with higher contribution of organic matter derived from marine phytoplankton. Diatoms identified from these cores are, in great part, marine species and genera, such as Actinoptychus splendens, Paralia sulcata, Coscinodiscus radiatus, Coscinodiscus sp and Thalassiosira sp. Continental taxa such as Actinella sp1, Aulacoseira, Eunotia zygodon, Desmogonium and Pinnularia were recorded only in one sample from the top of the core TSM8. Facies infomration, together with isotope, elementar, \'ANTPOT.14 C\', palinological, and diatom data, are consistent with the existence of a wave-dominated paleoestuary during the Late Pleistocene and Holocene in northeastern Marajó Island, previously to the establishment of Lake Arari. The initial stages proposed for the interruption of fluvial inflow to the paleoestuary Arari coincide with the formation of open vegetation in the island and the consequent reduction of mangrove areas at the mid Holocene. The effect of regional tectonics seems to have been of a great contribution to change the Marajó landscape during Pleistocene and Holocene. Divergency of relative sea level proposed for the Marajó Island with respect to the global pattern, combined with the increased record of tectonic activity in the Late Pleistocene and Holocene, led to the hypothesis of successive transgressions linked to tectonic subsidence as opposed to eustary. The transgression recorded before nearly 29,000 yr B.P. took place simultaneously to the pronounced tendency of sea level drop after the Last Interglacial Maximum. Additionally, the Holocene transgression in Marajó is recorded between 9,000 and 5,000 yr. B.P., thus it initiated before the global transgressive peak of the mid Holocene. During this period of eustatic rise, the relative sea level in Marajó Island started to stabilize, a process that culminated with a significant coast progradation at the end of this period. It is also unlikely that the change to open vegetation recorded from the mid Holocene had a climatic response, as this change took place simultaneously to climate fluctuation from relatively more arid to relatively more humid. The most likely hypothesis is that the open vegetation became established in eastern Marajó Island in response to hydrological changes, perhaps promoted by tectonic subsidence and subsequent estabilization, culminated with the recent coastline progradation.