Floodplain lakes in the Mississippi Alluvial Valley (MAV) provide valuable freshwater resources for states in which they occur. Thirty lakes in portions of Mississippi and Arkansas were surveyed for chlorophyll-a fluorescence and turbidity using handheld meters to determine relationships between chlorophyll-a concentrations and suspended solids. High applicability of handheld meters in the MAV presents economic benefits for monitoring the numerous lakes in the region. Additionally, twelve lakes within Bear Creek watershed, Mississippi were studied to determine how hydrologic connectivity shapes fish communities. Isolated and permanently connected floodplain lakes exhibited characteristically lacustrine and rheophilic fish communities, respectively, diversifying fishery management opportunities. Lastly, spring diel temperature and oxygen dynamics, as well as juvenile fish communities, were assessed within three habitats in a floodplain lake – pelagic environment, margin and contiguous wetlands. Variability in temperature and oxygen across the three habitats promotes spring habitat heterogeneity while supporting distinct but overlapping juvenile fish assemblages.

Located in central Brazil, the Araguaia River is the largest river flowing through the Cerrado, the Brazilian savanna. The thesis presented here assesses the hydro-geomorphology of the middle Araguaia River-floodplain system by characterizing flooding patterns and linking these patterns to the geomorphology of the floodplain. It also determines the response of floodplain lake morphometry and surface water connectivity to the annual flooding of the river, and describes how different floodplain geomorphologic units influence changes in open water areas in the floodplain from the dry season to the wet season. Peak discharges along the middle Araguaia River can be reduced downstream despite large increases in drainage area and the contribution of tributary inputs. After analyzing average daily discharge measurements from 1975 to 2007 along an upstream reach and a downstream reach in the middle Araguaia River, four main flooding types are characterized based on the magnitude of the peak discharge and the pattern of peak discharge reduction that occurs as the flood wave moves downstream. Short-term losses of channel discharge during the flooding peak and over the flooding season from November to May are estimated, with the downstream reach displaying more short-term channel loss compared to the upstream study reach. Differences in floodplain geomorphological characteristics between the two study reaches, including the proportions of distinct geomorphologic units (a lower elevation impeded floodplain, a unit dominated by paleomeanders, and a unit of accreted banks and islands), influence the patterns of peak reduction and channel loss. Short-term losses of channel discharge during flooding peaks are usually re-gained by the channel by the end of the flooding season, although in two years about 10% of the volume input into the downstream reach was lost from the channel over the flooding season. Using satellite imagery and an open water index, changes in lake area, perimeter, and surface water connectivity with the main channel between dry season and the wet season are determined for 32 floodplain lakes. The changes in lake morphometry and connectivity are linked to how fluvial processes formed the floodplain lakes. Spatial variations in the floodplain areas that became open water from the dry season to the wet season demonstrate that distinct floodplain geomorphologic units influence the extent and location of open water areas during flooding. Floodplain lakes that expand in area and in depth and are connected to the river channel via surface water likely provide storage areas for the channel losses and peak discharge reductions observed in some of the flooding types for the middle Araguaia River. Although there have been attempts to plan the placement of dams on the Araguaia River, the river is not impounded, allowing for the analysis of a river system with an unaltered flow regime. This thesis contributes to knowledge of a large and understudied tropical river in an ecologically sensitive region. / text

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-06-28T18:00:50Z No. of bitstreams: 1 moreira, 2008.pdf: 3355865 bytes, checksum: 22ec01a744345548acc67908e25fcd32 (MD5) / Made available in DSpace on 2017-06-28T18:00:50Z (GMT). No. of bitstreams: 1 moreira, 2008.pdf: 3355865 bytes, checksum: 22ec01a744345548acc67908e25fcd32 (MD5) / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / A Bacia Amazônica é acompanhada, ao longo do curso dos seus rios, por planícies de inundação. Sabe-se que estas regiões apresentam um grande potencial no armazenamento de matéria orgânica, que por sua vez, reservam importantes informações sobre mudanças climáticas ocorridas no passado. O conhecimento destas alterações pretéritas permite o entendimento de como os ecossistemas podem reagir a futuras mudanças no clima. Tendo em vista estas características, o objetivo deste estudo é reconstruir as mudanças pal eoambientais e paleohidrológicas do Lago Santa Ninha, na Várzea do Lago Grande de Curuai, localizada na margem direita do Rio Amazonas, à apr oximadamente 850 km da foz. Foram analisados dois testemunhos, denominados como TA12 e TA14 que apresentam, respectivamente, 2,10 e 2,70cm de compr imento. A determinação do teor de água, densidade aparente, granulometria e m ineralogia permitiram reconstruir a hidrodinâmica da região. A análise da composição da matéria orgânica, através da concentração de carbono e nitrogênio e d os isótopos estáveis δ 13 C e δ 15 N indicaram as alterações na vegetação e as dataçõe s por carbono 14 revelaram que o testemunho TA14 apresenta 5700 anos cal AP. E ste estudo colocou em evidencia diferentes ambientes sedimentares: na bas e do testemunho até 5000 anos cal AP temos uma vegetação inundada que foi gr adualmente substituída por bancos de gramíneas e por uma planície com secas sa zonais em 4000 anos cal AP até alcançar, desde 700 anos AP as condições atuais deste lago. Essas mudanças são interpretadas como a resposta a um aumento do n ível da água do rio durante as enchentes, que por sua vez são conseqüências de alt erações climáticas ocorridas na região / Amazonian Rivers are accompanied, during their cour se, by floodplains, which are named “várzeas”. It is known that these regions hav e a great potential in the storage of organic matter, which in turn, provides importan t information about climate change occurred in the past. Knowledge of these changes al lows the understanding of how ecosystem may respond to future changes in climate. The physical, chemical and geochemical characteristics of lacustrine sediments were studied to reconstructed paleohydrological control on sedimentation in an Am azonian floodplain. Two cores were collected at the Lago Grande de Curuai floodpl ain, in Santa Ninha lake, located on the right margin of the Amazon River at 850km of the estuary. Water content, granulometry, radiocarbon datation, microscopic ana lyses, organic carbon and nitrogen content and δ 13 C were used to characterize the sedimentary process es. The core TA12 is 210 cm-long and the TA14 has 270cm tha t correspond to 5700 years cal BP. The core points out different sedimentary environments: a flooded vegetation at the base of the core till 5000 cal yrs BP is sub stituted by graminea banks changing to a floodplain encompassing prolonged annual dryne ss at 4000 cal yrs BP. Since 700 BP the present day varzea lake, permanently ove rflooded, has been installed. These changes are interpreted as a response to an i ncrease in the level of water in the river during the floods, which in turn are cons equences of climate change occurring in the region

Made available in DSpace on 2016-06-02T19:29:50Z (GMT). No. of bitstreams: 1 TeseNMCN.pdf: 1178647 bytes, checksum: d18af7301e74a6724d6021f399155f9d (MD5) Previous issue date: 2003-06-30 / Financiadora de Estudos e Projetos / The phytoplankton communities of five lakes in the floodplain of Turiaçu River (MA) were analysed for taxonomic composition and evaluated regarding temporal dynamics. Changes on phytoplankton densities were analysed as well as the variations in physical and chemical water characteristics along a hydrological cycle, attempting to correlate them to the flood pulse and the consequent water level fluctuations. Samplings were carried out in lakes Cabeludo, Caboclo, Arrodiador, Bate Terra and Quebra Pote, five periods of representative phases: dry, water rising, flooding, water lowing and a second dry. Qualitative samples were taken by horizontal hauls with a 20 µm phytoplankton net, and quantitative samples were taken at the surface and at 20 cm above the bottom with a Van Dorn bottle. Samples were preserved with in 4% formalin and the phytoplankton was identified and enumerated in settling chambers under a Zeiss inverted microscope. Turbulence, rainfall and water level fluctuations were considered the main controlling factors of the successional dynamics. The lakes are shallow and nutrient rich, being eutrophic during the dry period and mesotrophic in the other hydrological phases. The phytoplankton communities of the five lakes are represented by 139 taxa belonging to 9 Classes: 22 Bacillariophyceae, 34 Chlorophyceae, 1 Cryptophyceae, 33 Cyanophyceae, 2 Dinophyceae, 20 Euglenophyceae, 1 Xanthophyceae and 25 Zignematophyceae. Most taxa are new records for Maranhão State. Cyanophyceae was the numerically dominant group in three periods: water rising (March), water lowing (August) and dry (December), with relative abundances varying from 23.13% in Lake Caboclo during the water raising period to 65.72% of the total, at the same lake, in the dry period. Bacillariophyceae were the most abundant organisms in the flooding period (May), with relative abundances varying from 38,14 % in Lake Bate-Terra to 49,70% in Lake Caboclo. The most abundant species of Cyanophyceae and Bacillariophyceae were Planktolyngbya circumcreta and Aulacoseira granulata, respectively. Total phytoplankton densities varied from 1725 ind.mL-1 in Lake Arrodiador, in the flood period, to 8272 ind.mL-1 in Lake Cabeludo, at the dry period. The highest densities occurred in dry periods, related to the greater nutrient availability and to the concentration factor resulting from the water level decrease. There was a tendency to higher species richness, lower dominance, higher equitativity and higher diversity of phytoplankton during water rising and water lowering. / As comunidades fitoplanctônicas de cinco lagos da planície de inundação do rio Turiaçu (MA) foram analisadas para a composição taxonômica e avaliadas de acordo com sua dinâmica temporal. As variações na densidade do fitoplâncton também foram avaliadas, assim como as mudanças nas características físicas e químicas da água dos lagos, ao longo de um ciclo hidrológico, buscando correlacioná-las com o pulso de inundação e as conseqüentes variações no nível de água dos lagos. As amostragens foram realizadas nos lagos Cabeludo, Caboclo, Arrodiador, Bate Terra e Quebra Pote, em cinco épocas representativas dos períodos: de seca, enchente, cheia, vazante e de um segundo período de seca, tendo sido realizadas coletas qualitativas, por meio de arrastos horizontais, com rede de 20 µm de abertura de malha e coletas quantitativas do fitoplâncton total, na superfície e 20 cm acima do fundo, com Garrafa de Van Dorn. As amostras foram preservadas em formalina 4% e quantificadas em câmaras de sedimentação, sob microscópio invertido Zeiss. A turbulência, a precipitação e as variações no nível d água foram consideradas os principais fatores controladores da dinâmica sucessional. Os lagos são rasos e suas águas ricas em nutrientes, sendo os lagos eutróficos nos períodos de seca e mesotróficos nos outros períodos hidrológicos. As comunidades fitoplanctônicas dos cinco lagos estão representadas por 139 táxons, distribuídos em 9 Classes: 22 Bacillariophyceae, 34 Chlorophyceae, 1 Cryptophyceae, 33 Cyanophyceae, 2 Dinophyceae, 20 Euglenophyceae, 1 Xanthophyceae e 25 Zignematophyceae. A maioria dos táxons são novas ocorrências para o estado do Maranhão. Cyanophyceae foi a classe numericamente mais abundante em três períodos: enchente (março), vazante (agosto) e seca (dezembro), com abundâncias relativas que variaram de 23,13% no lago Caboclo no período de enchente, a 65,72% do total, neste mesmo lago, no período de seca. Bacillariophyceae foi a classe mais abundante no período de cheia (maio), com abundância relativa variando de 38,14 % no lago Bate-Terra a 49,70% no lago Caboclo. As espécies mais abundantes das classes Cyanophyceae e Bacillariophyceae foram Planktolyngbya circumcreta e Aulacoseira granulata, respectivamente. As densidades totais do fitoplâncton variaram de 1.725 ind.mL-1 no lago Arrodiador, no período de cheia, a 8.272 ind.mL-1 no lago Cabeludo, no período de seca. As maiores densidades ocorreram nos períodos de seca, relacionadas à maior disponibilidade de nutrientes e ao fator de concentração, pela redução no nível de água. As comunidades tenderam a uma maior riqueza de espécies, menor dominância, maior uniformidade e maior diversidade nas fases de enchente e vazante.

Made available in DSpace on 2016-06-02T19:30:01Z (GMT). No. of bitstreams: 1 5864.pdf: 3534463 bytes, checksum: cd15fcfba13c323323c9b239d2f29ed8 (MD5) Previous issue date: 2014-03-06 / Financiadora de Estudos e Projetos / The study of diversity and productivity can contribute to understanding the functioning of Amazonian ecosystems as a whole and especially to the conservation of its aquatic biota, considered one of the richest in species on the planet. The present study aimed to analyze the course of three years the limnological characteristics of three floodplain lakes of the Madeira River in the area of influence of the Santo Antônio hydroelectric plant on the Madeira, in the region near to Porto Velho, Rondônia, with emphasis on the zooplankton community. Samples were quarterly covering the four major hydrological periods: low water, flood, high water and ebb over three years (2010-2013). Physical, chemical and biological variables of the lakes were collected and correlated with species composition, biomass and production of zooplankton. The zooplankton community was characterized by high species richness (195 taxa) and high degree of endemism for the group of Copepoda Calanoida. The results showed that the three lakes have eutrophic or mesotrophic characteristics. The highest values of density and biomass of zooplankton in the lake occurred Cujubim. The rotifers were numerically dominant, but the Copepoda dominated in biomass and secondary production in lakes Cuniã and San Miguel. There was little variability in secondary production of zooplankton, being slightly higher in the lake Cujubim with increased production of copepods and rotifers in this lake. The rainfall variation demarcated the occurrence of well-defined hydrological periods, directly affecting the hydrodynamics of this region, controlling population fluctuations of zooplankton, probably brought by the increased availability of resources on the Madeira River in the flood season, playing an important role in the organization of food webs, and how to link the transfer of matter and energy in food chains. / O estudo da diversidade e produtividade pode contribuir para o entendimento do funcionamento dos ecossistemas amazônicos como um todo e principalmente para a conservação da sua biota aquática, considerada uma das mais ricas em espécies no planeta. O presente estudo teve como objetivo analisar ao longo de três anos as características limnológicas de três lagos de várzea do rio Madeira na área de influência da Usina Hidroelétrica Santo Antônio do Madeira, na região próxima a Porto Velho, Rondônia, com ênfase na comunidade zooplanctônica. As amostragens foram trimestrais abrangendo os quatro períodos hidrológicos principais: Águas baixas, enchente, águas altas e vazante, ao longo de três anos (2010-2013). Foram coletadas variáveis físicas, químicas e biológicas dos lagos, correlacionando com a composição de espécies, além de determinadas a biomassa e a produção da comunidade zooplanctônica. A comunidade zooplanctônica foi caracterizada por elevada riqueza de espécies (195 táxons) e alto grau de endemismo para o grupo dos Copepoda Calanoida. Os resultados obtidos evidenciaram que os três lagos apresentam características mesotróficas ou eutróficas. Os maiores valores de densidade e biomassa da comunidade zooplanctônica ocorreram no lago Cujubim. Os Rotifera foram numericamente dominantes, mas os Copepoda dominaram em biomassa e produção secundária, nos lagos Cuniã e São Miguel. Houve pequena variabilidade na produção secundária da comunidade zooplanctônica, sendo ligeiramente superior no lago Cujubim, com maior a produção de Copepoda e Rotifera neste lago. A variação pluviométrica demarcou a ocorrência de períodos hidrológicos bem definidos, afetando diretamente a hidrodinâmica desta região, controlando flutuações populacionais da comunidade zooplanctônica, provavelmente pela maior disponibilidade de recursos trazidos do rio Madeira nos períodos de cheia, desempenhando papel importante na organização das teias tróficas, e como elo de transferência de matéria e energia nas cadeias alimentares.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2018-03-01T17:33:16Z No. of bitstreams: 1 Dissertação_Julia Duarte Contrera.pdf: 4179003 bytes, checksum: 954048867c122e6fc6c2ef65e6573276 (MD5) / Made available in DSpace on 2018-03-01T17:33:16Z (GMT). No. of bitstreams: 1 Dissertação_Julia Duarte Contrera.pdf: 4179003 bytes, checksum: 954048867c122e6fc6c2ef65e6573276 (MD5) / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / A Bacia Amazônica é um importante agente de influência das mudanças climáticas, podendo atuar tanto como sumidouro quanto como emissor de CO2 para a atmosfera. Existem diversos estudos sobre a atuação de sistemas Amazônicos na ciclagem de carbono. Entretanto estudos relacionados à atuação de planícies alagadas amazônicas a cerca do acúmulo de carbono ainda são muito escassos. Nesse contexto o presente trabalho tem como objetivo avaliar as mudanças paleohidrológica, paleoclimáticas que ocorreram no Lago Airo durante os últimos 13 mil anos e como essas mudanças afetaram o acúmulo de carbono em um sistema lacustre localizado na Sub-bacia do Rio Negro. Nesta área de estudo foi coletado um testemunho denominado AIRO12/01, com 1,46 cm de comprimento que apresentou ao longo dos últimos 13300 anos cal AP três fases distintas de sedimentação. Durante o período entre 13300 anos cal AP a 11700 anos cal AP o lago constituía um canal do Rio Negro, durante esse período foi observada a ocorrência de um clima úmido na região evidenciada pela granulometria arenosa (Argila: 0,2%, Silte, 0,1% Areia: 99,63%) que indicou forte influência fluvial. Em 13300 anos cal AP foi observado um evento de sedimentação abrupta que pode ser consequência de fortes chuvas ou pelo aumento da vazão do Rio Negro. Os baixos valores de pigmentos sedimentares (média de 2,9 SPDU) indicaram baixa produtividade lacustre que ocorre devido a forte influência fluvial. Os valores de δ13C indicaram uma maior contribuição de plantas terrestres na constituição da matéria orgânica lacustre. A forte influencia do Rio Negro sobre o lago neste período também foi registrada através de altos valores de C/N (valor médio de 49,4, como reflexo da influência de ácidos húmicos característico deste sistema fluvial) e valores de 15N próximos a zero (representativo de forte entrada de material terrestre). Devido a forte influência que o Rio exercia sobre o lago os valores de COT encontrados eram baixos (média de 1,37%). O período entre 11700 e 3000 anos cal AP foi marcado por evidencias de clima mais seco, com um aumento da concentração de micropartículas de carvão com media de 104 μm² e evidência de atividade eólica observada a partir de analise estatística. Contudo foram observados valores mais elevados de pigmentos sedimentares (média de 8,72 SPDU) e uma leve elevação dos valores de COT (média de 2,90%) que sugerem um período de semi-isolamento do Rio. A granulometria nesse período continua arenosa, mas com uma pequena variação na proporção de seus constituintes (Argila: 1,57%; Silte: 5,18%, Areia:93,24%) . Durante os últimos 3000 anos cal AP é possível observar condições climáticas mais úmidas neste registro sedimentar, evidenciadas pelo aumento da concentração de pigmentos sedimentares (média de 13 SPDU) e do COT (média de 34%). A análise granulométrica torna-se mais siltosa (Argila: 13,10%, Silte: 78,31%, Areia: 8,59%) e a razão C/N apresentou acentuado decréscimo (média de 31,2), indicando que a influência fluvial diminuiu a partir desse período. Com a diminuição da influência fluvial foi observado o aumento da produtividade lacustre a partir do aumento do δ15N. O isolamento do lago em relação ao rio pode ter ocorrido devido ao aumento da umidade na região que permite o desenvolvimento da vegetação no entorno do lago Airo como é observado nos dias atuais. A partir do Holoceno Superior também é observado o aumento na concentração de micropartículas de carvão (valor médio de 3x106 partículas por grama) e do tamanho médio das partículas (644 μm²), que podem indicar atividade humana no local. / The Amazon Basin is an important and arguably key component of the carbon cycle due to its role in the carbon storage and also amenable to fast release to the atmosphere throughout land use change or drought-induced feedbacks.Despite the numerous studies about carbon stocks in the Amazonian soils and biomass little is known about the carbon accumulation in the floodplain lakes. In this context, the objective of this work is to evaluate the paleohydrological and paleoclimatic changes in Lake Airo during the last 13,000 years and how those changes affected the carbon accumulation in a floodplain lake located in the Negro river Sub-basin. In this study area a 146 cm core denominated AIRO12/01 was collected. Dated by four AMS-radiocarbon dates, this core has a basal age of 13300 cal years BP and three sedimentary units were identified. During the period between 13300 years cal BP to 11700 years cal BP was observed the occurence of humid climate in the region, evidenced by a grain size with higher proportions of sand (Clay: 0.2%, Silte 0.1 %, Sand: 99.63%) that indicates a strong fluvial influence. In addition an abrupt sedimentation event was observed at 13300 years cal BP interpreted as a consequence of heavy rains. The low values of Chlorophyll derivatives (average of 2.9 SPDU) indicate low lacustrine productivity that occurs due to strong lake influence. The values of δ13C indicated a greater proportion of terrestrial plants in the lacustrine organic matter. The strong influence of Negro river on the river in this period was also recorded by high C/N values (average value of 49.4 as a reflection of the influence of humic acids typical of this river system) and values of δ15N near to zero, representing a strong input of terrestrial material. Due to the strong river influence a extremely low TOC values was observed (average of 1.37%). Between 13300 and 11700 years cal BP the lake constituted a channel of the Negro River. The period between 11700 and 3000 years cal BP was characterized by a dry climate evidenced by an increase in the concentration of microparticles of charcoal (average of 2.4 x 106 particles per gram) and eolian activity observed from statistical analysis. The low charcoal particle size of this period (average of 104 μm2) may suggest the occurrence of regional paleofires. However, higher values of Chlorophyll derivatives (average 8.72 SPDU) and sligth elevation of TOC values (average of 2.90%) were observed suggesting a period of semi-isolation of the River. During this period the grain size was composed by higher concentration of sand, but with a small variation in proportion of its constituents (Clay: 1.57%, Silte: 5.18%, Sand: 93.24%). The last 3000 years BP was characterized by a wetter climate, evidenced by the increase of the chlorophyll derivatives (average 13 SPDU) and TOC (average of 34%). This phase was marked by a transition by a transition from coarse to finer sediments (Clay: 13.10%, Silt: 78.31%, Sand: 8.59%) and C/N ratio showed a significant decrease (average 31.2), indicating a reduction in the river influence. As a consequence a increase in the lacustrine productivity and in the δ15N values was observed during this period. The reduction of the river influence can be due to the increase of humid conditions which allowed the development of vegetation around the Lake Airo, as it is observed today. An increase in the concentration of microparticles of charcoal (mean values of 3 x 106 particles per gram) was observed. In addition the increase in the charcoal particle size (644 m) that characterized this period may indicate human activity around Airo Lake

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-04-26T17:27:20Z No. of bitstreams: 1 TeseKAniceto.pdf: 7215824 bytes, checksum: b930fcc52874c9e437f1d692f113bde8 (MD5) / Made available in DSpace on 2016-04-26T17:27:20Z (GMT). No. of bitstreams: 1 TeseKAniceto.pdf: 7215824 bytes, checksum: b930fcc52874c9e437f1d692f113bde8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ / As variações paleohidrológicas pelas quais passaram os lagos Hubos e Quistococha ao longo do Holoceno Médio e Superior, foram reconstruídas através de análises semi-quantitativas e qualitativas dos argilo-minerais e dos elementos Al, Si, S, K, Ca, Mn Ti, Fe, Rb, Sr e Zr. A fim de avaliar como o Rio Amazonas influencia os processos sedimentares destes ecossistemas, determinou-se a concentração elementar de carbono (carbono orgânico total-COT) e nitrogênio (nitrogênio total-NT), composição isotópica do carbono e nitrogênio (δ13C e δ15N). O Lago Hubos, está situado próximo à confluência dos rios Ucayali e Marañon, faz parte da planície de inundação do Rio Ucayali e sua conexão com o canal principal se dá de forma indireta e através do pequeno rio Yarapá e sua distância do canal rio é de aproximadamente 2 km. A sedimentação do lago Hubos nos últimos 4130 anos cal AP, se deu sob a influência da forte dinâmica do Ucayali, que resultou em datações 14C invertidas ou com idades muito próximas em trechos extensos do testemunho. Entre 4130 e 2870 anos cal AP a concentração de COT era baixa (<1%), os valores de δ13C e δ15N do lago apresentaram uma matéria orgânica que é mistura de fitoplancton e com matéria orgânica típica de solos e plantas C3 e a presença de laminações, o que sugere um sistema de baixa energia hidrodinâmica. A assembléia mineral com assinatura típica do Ucayali, apresentou elevados percentuais de esmectita (~61%), caulinita (~15%), clorita (~8%) e ilita (18%) e a mineralogia por FRX sugere variabilidade da maior parte dos dados, sugerindo pulsos de inundação neste período. Uma lacuna na sedimentação foi observada entre 2870 e 700 anos cal AP (unidade III). Este sedimento foi caracterizado por concentrações mais elevadas de COT (4,3%), matéria orgânica originada de plantas C3, elevados percentuais de esmectita (67%), caulinita (~12%), clorita (~6%) e ilita (15%) e predominância de material intemperizado e grosso no sedimento. Após esse período, o material sedimentado era pós-moderno e bioturbado, as concentrações de COT de 2,1% e esmectita (~52%), caulinita (~29%), clorita (~4%) e ilita (15%), esta matéria orgânica é característica de solos e plantas C3, com redução de frações mais grossas no sedimento e aumento de material inalterado. O material mais superficial é antigo, provavelmente retrabalhado, com concentração de COT 1,29% e esmectita (~46%) caulinita (~12%), clorita (~26%) e ilita (18%). A FRX, sugere material de granulometria mais grossa e mais alterado quimicamente. O lago Quistococha faz parte da Reserva Quistococha, e está localizado à 10 km do centro da cidade de Iquitos e aproximadamente 10 Km do rio Amazonas. Entre cerca de 6.100 e 4.900 anos cal AP, o lago estava sob forte influência do rio Amazonas. O que induziu a maiores taxas de sedimentação (~0,5 cm ano-1), a deposição predominante foi de partículas relativamente grossas (silte grosso) e laminadas, em detrimento do material orgânico (~5%). A mineralogia da fração argila determinou percentuais de esmectita (~41%), clorita (~9%), ilita (~20%), e caulinita (~29%). A razão FRX, sugere presença de material alterado quimicamente e laminações de 0,7 cm de espessura. A diminuição da granulometria e da espessura das laminações a partir de 5800 anos cal AP, até seu completo desaparecimento indicam a perda gradual da influência do Amazonas. Um hiato foi observado a partir de 4.900 anos calAP, cujo motivo provável ainda precisa ser investigado. Condições mais seca do Holoceno Médio impediram a volta da sedimentação, que só aconteceu apos 2600 anos cal AP, com o retorno das condições mais úmidas estabelecidas durante o Holoceno Tardio. A perda da influência do rio Amazonas induziu alterações significativas na sedimentação lacustre, determinando sua atual condição de isolamento. Caracterizado por taxas de sedimentação extremamente baixas (0,02 cm ano-1), sedimentos mais finos, ricos em material orgânico (20-80%) e fração argila composta de esmectita (~35%); clorita (~5%); ilita (~16%); e caulinita (~44%) / The palaeo-hydrological variations through which passed Hubos and Quistococha lakes along the Middle and Upper Holocene were reconstructed using a semi-quantitative and qualitative analyzes of clay minerals and the elementsAl, Si, S, K, Ca, Mn Ti, Fe, Rb, Sr e Zr. In order to assess how the Amazon River influences the sedimentary processes of these ecosystems, was determined the elementary concentration of carbon (total organic carbon-TOC) and nitrogen (total nitrogen-NT), isotopic composition of carbon and nitrogen (δ13C and δ15N). The Hubos Lake, is situated near the Ucayali and Marañon rivers confluence, part of the floodplain of the Ucayali river and its connection with the main channel occurs indirectly and through small river Yarapá and its distance from the river channel is aproximately2 Km. The sedimentation of the lake Hubos in the last 4130 years cal BP, occurred under the influence of the strong dynamics of the Ucayali, which resulted in 14C datings reversed or very close in age in extensive excerpts of testimony . Between 4130 and 2870 years cal AP TOC concentration was low (<1%), the values of δ13C and δ15N of lake showed an organic matter which is mixed with phytoplankton and typical organic matter from soils and plants C3 and the presence of laminations, which suggests a system of low hydrodynamic energy. The mineral meeting with the typical signature of Ucayali showed high percentages of smectite (~ 61%), kaolinite (~ 15%), chlorite (~ 8%) and illite (18%) and mineralogy by XRF suggests variability of most data, suggesting flood pulses during this period. A gap in sedimentation was observed between 2870 and 700 cal years BP (Unit III). This sediment was characterized by higher concentrations of TOC (4.3%), organic matter originating from plants C3 smectite high percentage (67%), kaolinite (~ 12%), chlorite (~ 6%) and illite (15 %) and predominance of the weathered and coarse sediment. After this period, the settled material was postmodern and bioturbed, TOC concentrations of 2.1% and smectite (~ 52%), kaolinite (~ 29%), chlorite (~ 4%) and illite (15%) this organic matter is characteristic of soils and C3 plants, with reducing coarser fractions in the sediment and unaltered material increase. The most superficial material is old, probably reworked, with 1.29% TOC concentration and smectite (~ 46%) kaolinite (~ 12%), chlorite (~ 26%) and illite (18%). The XRF suggests a thicker granulometry and chemically altered material. The Quistococha lake is part of Quistococha Reserve, and is located 10 km from the center of Iquitos city and approximately 10 km of the Amazon River. Between about 6100 and 4900 years cal BP, the lake was under strong influence of the Amazon River. What led to higher sedimentation rates (~ 0.5 cm-1 year), was the predominant deposition of relatively coarse particles (coarse silt) and laminated, to the detriment of the organic material (~ 5%). The the clay fraction mineralogy determined percentage of smectite (~ 41%), chlorite (~ 9%), illite (~ 20%), and kaolinite (~ 29%). The XRF reason, suggests the presence of chemically altered material and laminations of 0.7 cm thick. The decrease of granulometry and the laminations thickness from 5800 cal years BP, until its complete disappearance indicate the gradual loss of the Amazon influence. A gap was observed from 4900 cal years BP, whose probable reason still needs to be investigated. Drier conditions in the Middle Holocene prevented the sedimentation return, which only happened after 2600 cal years BP, with the return of most humid conditions established during the late Holocene. The loss of influence of the Amazon river induce significant changes in lacustrine sedimentation, determining its current condition of isolation. Characterized by extremely low sedimentation rates (0.02 cm year-1), fine sediments, rich in organic material (20-80%) and clay fraction composed of smectite (~ 35%); chlorite (~ 5%); illite (~ 16%); and kaolinite (~ 44%)

Floodplain lakes are strongly regulated by river connectivity because floodwaters exert strong influence on the water balance, the physical, chemical and biological limnological conditions, and the influx of contaminants. The Peace-Athabasca Delta (PAD) in northern Alberta (Canada) is a hydrologically complex landscape and is an important node in the upper Mackenzie River Drainage Basin. The ecological integrity of the PAD is potentially threatened by multiple environmental stressors, yet our understanding of the hydroecology of this large floodplain remains underdeveloped. Indeed, ever since the planning and construction of the WAC Bennett Dam (1960s), concerns have grown over the effects of upstream human activities on the lakes of the PAD. More recently, concerns over the health of the PAD have intensified and come to the fore of national and international dialogue due to water abstraction and mining and processing activities by the rapidly expanding oil sands industry centred in Fort McMurray Alberta. Currently, widespread perception is that upstream human activities have reduced water levels and frequency of flooding at the PAD, which have lowered nutrient availability and productivity of perched basin lakes, and have increased supply of pollutants from oil sands. However, these perceptions remain based on insufficient knowledge of pre-impact conditions and natural variability. Current and past relations between hydrology and limnology of PAD lakes are mostly undocumented, particularly during the important spring freshet period when the effects of river flood waters are strongest. Similarly, knowledge of the deposition of oil-sands- related contaminants in the PAD remains insufficient to determine whether anthropogenic activities have increased the deposition of important oil-sands-related contaminants such as polycyclic aromatic compounds (PACs) relative to natural processes. Such knowledge gaps must be filled to achieve effective monitoring, policy and governance concerning impacts of industrial development and the protection of human and environmental health within the PAD and Mackenzie drainage basin. This thesis examines the effects of river flooding (and the lack of) on water clarity, nutrients, chemistry, phytoplankton abundance, epiphyton community composition and the deposition of polycyclic aromatic compounds (PACs) in lakes of the Peace-Athabasca Delta. To determine the role of flooding on contemporary epiphytic diatom communities (an abundant and diverse guild of primary producers in PAD lakes), a field experiment was conducted examining the community composition and abundance of epiphytic diatoms in four PAD lakes. Two of these four lakes had received floodwaters that spring and two had not. Epiphytic diatom communities in each lake were sampled during the peak macrophyte biomass period (summer) from two macrophyte taxa (Potamogeton zosteriformis, P. perfoliatus var. richardsonii) and from polypropylene artificial substrates previously deployed that spring. A two-way analysis of similarity (ANOSIM) test identified that epiphytic diatom community composition differed between lakes that flooded and those that did not flood. From the use of similarity percentage (SIMPER) analysis, diatom taxa were identified that discriminate between flooded and non-flooded lakes. The relative abundance of ‘strong flood indicator taxa’ was used to construct an event-scale flood record spanning the past ~180 years using analyses of sedimentary diatom assemblages from a closed-drainage lake (PAD 5). Results were verified by close agreement with an independent paleo-flood record from a nearby flood-prone oxbow lake (PAD 54) and historical records. Comparison of epiphytic diatoms in flooded and non-flooded lakes in this study provides a promising approach to detect changes in flood frequency, and may have applications for reconstructing other pulse-type disturbances such as hurricanes and pollutant spills. Additionally, this study demonstrates that artificial substrates can provide an effective bio-monitoring tool for lakes of the PAD and elsewhere. To improve our understanding of the hydrolimnological responses of lake in the PAD to flooding, repeated measurements over three years (2003-05) were made on a series of lakes along a hydrological gradient. This allowed the role of river flooding to be characterized on limnological conditions of lakes and to identify the patterns and timescales of limnological change after flooding. River floodwaters elevate lake water concentrations of suspended sediment, total phosphorus (TP), SO4 and dissolved Si (DSi), and reduce concentrations of total Kjeldahl nitrogen (TKN), DOC and most ions. River flooding increases limnological homogeneity among lakes, because post-flood conditions are strongly affected by the river water properties. After floodwaters recede, limnological conditions become more heterogeneous among lakes in response to diversity of local basin influences (geology, slope, vegetation, depth, fetch, and biological communities and processes), and limnological changes occur at two distinct timescales. In the weeks to months after flooding, water clarity increases as suspended sediments and TP settle out of the water column. In the absence of flooding for many years to decades, evaporative concentration leads to an increase in most nutrients (TKN, inorganic N, and dissolved P), DOC and ions. Contrary to a prevailing paradigm, these results suggest that regular flooding is not required to maintain high nutrient concentrations. In light of anticipated declines in river discharge, limnological conditions in the southern Athabasca sector will become increasingly less dominated by the short-term effects of flooding, and resemble nutrient- and solute-rich lakes in the northern Peace sector that are infrequently flooded. To determine the roles of the Athabasca River and atmospheric transport as vectors for the deposition of PACs in the PAD, sediment cores spanning the last ~200 years were collected from three lakes within the delta. A closed-drainage basin elevated well above the floodplain (PAD 18) was selected to determine temporal patterns of change in PAC concentration due to atmospheric deposition and within-basin production of PACs. Known patterns of paleohydrological changes at the other two lakes (PAD 23 and 31) were used to assess the role of the Athabasca River in delivering PACs to the Athabasca Delta during the ~200 year. Well- dated sediment core samples were analysed for 52 alkylated and non-alkylated PACs (method EPA 3540/8270-GC/MS). Sediments deposited in the non-flood prone lake (PAD 18) contained lower concentrations of total PACs compared to sediments deposited during flood-prone periods in the other study lakes, and were dominated by PACs of a pyrogenic rather than bitumen origin. Multivariate analysis of similarity tests identified that the composition of PACs differs between sediments deposited during not flood-prone and flood-prone periods. Subsequent Similarities Percentage (SIMPER) analysis was used and identified seven PACs that are preferentially deposited during flood-prone periods. These seven PACs are bitumen-associated, river-transported and account for 51% of the total PACs found in oil-sands sediment. At PAD 31, which has been flood-prone both before and since onset of Athabasca oil sands development, identified no measureable differences in both the proportion and concentration of the river-transported indicator PACs in sediments deposited pre-1940s versus post-1982. Our findings suggest that natural erosion of exposed bitumen along the banks of the Athabasca River and its tributaries is the main process delivering PACs to the Athabasca Delta, and that the spring freshet is a key period for contaminant mobilization and transport. Such key baseline environmental information is essential for informed management of natural resources and human-health concerns by provincial and federal regulatory agencies and industry, and for designing effective long-term monitoring and surveillance programs for the lower Athabasca River watershed in the face of future oil sands development. Further monitoring activities and additional paleolimnological studies of the depositional history of PACs and other oil-sands- and non-oil-sands-related contaminants is strongly recommended. Overall, results of this research identify that river flooding exerts strong control on physical, chemical and biological conditions of lakes within the PAD. However, contrary to prevailing paradigms, the PAD is not a landscape that has been adversely and permanently affected by regulation of the Peace River and industrial development of the oil sands along the Athabasca River. Instead, data from contemporary and paleolimnological studies identify that natural processes continue to dominate the delivery of water and contaminants to the delta. Regular and frequent flooding is not essential to maintain the supply of nutrients and productivity of delta lakes, which has been a widespread paradigm that developed in the absence of objective scientific data. Instead, nutrient concentrations rise over years to decades after flooding and lake productivity increases. During the thesis research, novel approaches were developed and demonstrated to be effective. Namely, new artificial substrate samplers were designed for aquatic biomonitoring that accrue periphyton and can identify the occurrence of flood events. Also, paleolimnological methods were employed to characterize the composition and concentration of PACs supplied by natural processes prior to oil sands industrial activity, which serves as an important benchmark for assessing industrial impacts. These are effective methods that can be employed to improve monitoring programs and scientific understanding of the factors affecting this world-renowned landscape, as well as floodplains elsewhere.

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