Dissertations / Theses on the topic 'Limnology'

Orientador: Antonio Fernando Monteiro Camargo<br>Coorientador: Daercy Maria Monteiro de Rezende Ayroza<br>Banca: Matheus Nicolino Peixoto Henares<br>Banca: Gianmarco Silva David<br>Resumo: Objetivou-se avaliar a influência das variáveis limnológicas e da velocidade da corrente no desenvolvimento de Limnoperna fortunei e no recrutamento de novos indivíduos em áreas com tanques-rede, no Reservatório Canoas II, no Rio Paranapanema. Mensalmente de agosto/2016 a janeiro/2017 em campo foram realizadas medições de: transparência, oxigênio dissolvido potencial hidrogeniônico, condutividade elétrica e sólidos totais dissolvidos. Além destes, a água foi coletada e armazenada em frascos para serem analisadas em laboratório: nitrogênio total, nitrito, nitrato, amônia, fósforo total, ortofosfato, cálcio, alcalinidade, dureza e clorofila a. Medições de velocidade da corrente da água foram obtidas utilizando um fluxômetro e um ADCP. As amostras de larvas de L. fortunei foram obtidas utilizando bomba de sucção e rede de plâncton de 40 μm. Foram confeccionados substratos de madeira em cruz para contagem e medição do tamanho de larvas fixados. As variáveis limnológicas foram investigadas por meio da Análise de Componentes Principais (ACP). A comparação entre o comprimento dos indivíduos nas duas áreas avaliadas e a medição da velocidade de corrente com o ADCP foi realizada por meio de Box Whisker Plot. Os resultados de velocidade de corrente da água com o fluxômetro e a da relação entre densidade de larvas na coluna d'água e número de indivíduos fixados foi feita com o auxílio de gráficos. As variáveis limnológicas podem ter influenciado no desenvolvimento do L. fortunei, princi... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: The objective of this study was to evaluate the influence of limnological variables and current velocity on the development of Limnoperna fortunei and the recruitment of new individuals in areas with network tanks in the Canoas II Reservoir on the Paranapanema River. Monthly from August / 2016 to January / 2017 in the field measurements were made of: transparency, dissolved oxygen potential hydrogen, electrical conductivity and total dissolved solids. In addition, water was collected and stored in bottles to be analyzed in laboratory: total nitrogen, nitrite, nitrate, ammonia, total phosphorus, orthophosphate, calcium, alkalinity, hardness and chlorophyll a. Water current velocity measurements were obtained using a flow meter and an ADCP. Samples of larvae of L. fortunei were obtained using a suction pump and 40 μm plankton net. Crosswood substrates were made for counting and measuring the size of fixed larvae. Limnological variables were investigated through Principal Component Analysis (PCA). The comparison between the length of the individuals in the two areas evaluated and the current velocity measurement with the ADCP was done by means of Box Whisker Plot. The results of current velocity of the water with the flowmeter and of the relation between larval density in the water column and number of fixed individuals was done with the aid of graphs. Limnological variables may have influenced the development of L. fortunei, especially in TR2. It has not been proven that water ... (Complete abstract click electronic access below)<br>Mestre

This thesis presents the results of contemporary limnological and palaeolimnological investigations of a series of crater lakes in order to reconstruct the palaeoenvironmental history of western Uganda, East Africa. The research examines questions of spatial and temporal heterogeneity of climate changes in the context of growing human impacts on the landscape over the last millennium. Sediment records from two lakes, Nyamogusingiri and Kyasanduka within the Queen Elizabeth National Park (QENP) were investigated to look at the long term records of climate and environmental change (spanning the last c. 1000 years). Five shorter cores across a land-use gradient were retrieved to assess the impact of human activity on the palaeoenvironmental record over the last ~150 years. High-resolution (sub-decadal), multiproxy analyses of lake sediment cores based on diatoms, bulk geochemistry (C/N and δ13C) and sedimentary variables (loss-on-ignition, magnetic properties and physical properties) provide independent lines of evidence that allow the reconstruction of past climate and environmental changes. This multiproxy approach provides a powerful means to reconstruct past environments, whilst the multi-lake approach assists in the identification and separation of local (e.g. catchment-scale modifications and groundwater influences) and regional effects (e.g. climatic changes). The results of a modern limnological survey of 24 lakes were used in conjunction with diatom surface sediment samples (and corresponding water chemistry) from 64 lakes across a natural conductivity gradient in western Uganda (reflecting a regional climatic gradient of effective moisture) to explore factors controlling diatom distribution. The relationships between water chemistry and diatom distributions were explored using canonical correspondence analysis (CCA) and partial CCA. Variance partitioning indicated that conductivity accounted for a significant and independent portion of this variation. A transfer function was developed for conductivity (r2jack = 0.74). Prediction errors, estimated using jack-knifing, are low for the conductivity model (0.256 log units). The final model was applied to the core sediment data.This study highlights the potential for diatom-based quantitative palaeoenvironmental reconstructions from the crater lakes in western Uganda. Sedimentary archives from the Ugandan crater lakes can provide high-resolution, annual to sub-decadal records of environmental change. Whilst all of the lakes studied here demonstrate an individualistic response to external (e.g. climatic) drivers, the broad patterns observed in Uganda and across East Africa suggest that the crater lakes are indeed sensitive to climatic perturbations such as a dry Mediaeval Warm Period (MWP; AD 1000-1200) and a relatively drier climate during the main phase of the Little Ice Age (LIA; c. AD 1500-1800); though lake levels in western Uganda do fluctuate, with a high stand c. AD 1575-1600). The general trends support the hypothesis of an east to west (wet to dry) gradient across East Africa during the LIA, however, the relationship breaks down and is more complex towards the end of the LIA (c. AD 1700-1750) when the inferred changes in lake levels at Nyamogusingiri and Kyasanduka are synchronous with changes observed at Lakes Naivasha (Kenya) and Victoria and diverge from local lake level records (from Edward, Kasenda and Wandakara). Significant changes in the lake ecosystems have occurred over the last 50-75 years, with major shifts in diatom assemblages to benthic-dominated systems and an inferred increase in nutrient levels. These changes are coincident with large sediment influx to the lakes, perhaps as a result of increasing human activity within many of the lake catchments.

Coldwater Lake and Castle Lake are two new lakes which were formed in the aftermath of the volcanic eruption of Mount St . Helens, WA in May, 1980. This research describes the limnology of these lakes ten years later, and includes physical, chemical, and biological parameters. The two lakes are compared and contrasted. Previous research on the eruption and its aftermath, as well as earlier studies of the lakes are described.

O presente estudo teve por objetivo avaliar a qualidade dos compartimentos água e sedimento do rio Monjolinho, localizado na sub-bacia hidrográfica do Alto Jacaré-Guaçu, na região centro-norte do estado de São Paulo. Para tanto, foram realizadas análises limnológicas e ecotoxicológicas em seis estações de amostragem ao longo do rio, durante cinco campanhas de coleta (julho, outubro de 2003 e janeiro, abril, julho de 2004). Os ensaios de toxicidade com amostras ambientais foram realizados com os cladóceros planctônicos Daphnia similis e Ceriodaphnia dubia como organismos-teste. Adicionalmente, foram realizados testes de sensibilidade aos metais cádmio e cobre utilizando Daphnia similis e Ceriodaphnia dubia, com o intuito de verificar se as concentrações permitidas pelo CONAMA 357/05 para estes metais são adequadas para a proteção da vida aquática em rios de classe 2. Os resultados obtidos quanto as análises limnológicas apontaram três trechos distintos do rio Monjolinho considerando-se a qualidade da água: a) trecho não poluído a ligeiramente poluído (estação 1); b) trecho poluído (estações 2, 3, e 4) e c) trecho fortemente poluído (estações 5 e 6). Os ensaios de toxicidade com amostras ambientais indicaram uma maior toxicidade do sedimento do que da água, particularmente nos períodos de outubro de 2003, janeiro e abril de 2004. Neste contexto, os testes com sedimento foram mais adequados para uma avaliação da real condição de toxicidade do sistema. Quanto aos testes de sensibilidade, os resultados para cádmio foram superiores ao limite estabelecido pela resolução 357 do CONAMA/05 (1 &#956g/L), demonstrando adequabilidade do valor estabelecido para a manutenção da vida aquática em rios de classe 2, no que se refere ao efeito isolado deste metal. Já os valores encontrados nos testes de sensibilidade ao cobre foram inferiores ao limite para cobre dissolvido estabelecido pelo CONAMA 357/05 (9 &#956g/L), mostrando que o valor definido para a manutenção da biota aquática ainda não está adequado, levando-se em consideração o efeito isolado deste contaminante.<br>The present study aimed to evaluate water and sediment quality of Monjolinho river, located at High Jacaré-Guaçu water basin, in the center of São Paulo state. Limnological and ecotoxicological analyses were carried out in six sampling stations along the river, during five sampling periods (July, October of 2003 and January, April, July of 2004). Bioassays with environmental samples were carried out with planktonic crustaceans, Daphnia similis and Ceriodaphnia dubia, as test organisms. Additionally, tests of sensibility to cadmium and copper were carried out with the same species to verify if their allowed concentrations by CONAMA 357/05 are appropriate for the protection of the aquatic life in class 2 rivers. The results of the limnological analyses indicated three distinct regions of water quality: a) not polluted to slightly polluted region (station 1); b) polluted region (stations 2, 3, and 4) and c) highly polluted region (stations 5 and 6). The bioassays with environmental samples indicated greater sediment toxicity than water toxicity, particularly in October of 2003, January and April of 2004. The tests of sensibility to cadmium, showed higher values than the limit established by resolution 357 of CONAMA/05 for this metal (1 &#956g/L), demonstrating adequacy of the established value for the maintenance of the aquatic life in class 2 waters, concerning the isolated effect of cadmium. However, the tests of sensibility to copper, presented lower values than its limit established by CONAMA 357/05 (9 &#956g/L), showing that the determined value of copper for the maintenance of the aquatic biota is still not adequate, considering the isolated effect of this pollutant.

Entre os diversos impactos nos ecossistemas aquáticos, a construção de reservatórios talvez represente um dos principais agentes modificadores, inserindo alterações físicas, químicas e biológicas nos sistemas antes e após a sua construção. No Brasil, tal impacto também é singular, verificando-se o aproveitamento dos mesmos para a construção de barragens, principalmente as construídas em cascatas (sistemas Paranapanema, Tietê e São Francisco por exemplo), sendo que, neste padrão de construção, espera-se, na maioria das vezes, um efeito crescente do controle da qualidade da água, com o primeiro reservatório mais eutrófico que os demais por sua capacidade de reter materiais provenientes dos principais tributários. No estado de São Paulo, na região Sudeste, destacam-se os reservatórios de Barra Bonita, Bariri, Ibitinga, Promissão, Nova Avanhandava, e Três Irmãos. Visando avaliar os impactos e contribuir com informações para monitorar as condições ambientais desses reservatórios, foram realizadas coletas de água e sedimento em quatro períodos distintos (outubro/99, fevereiro, maio e julho/00), em 15 estações de coleta, incluindo estações nos rios Tietê e Piracicaba e à montante e à jusante da barragem de cada um dos seis reservatórios, bem como no rio Bauru (um afluente bastante impactado de toxicidade com amostras de água e sedimento, utilizando-se Daphnia similis (em bioensaios de toxicidade aguda) e Ceriophnia dubia (em bioensaios de toxicidade crônica), análises de metais totais na água e biodisponíveis no sedimento, além do monitoramento de variáveis limnológicas (temperatura, pH, condutividade, oxigênio, dissolvido, material em suspensão, clorofila-a, nutrientes totais e dissolvidos). Os resultados obtidos para as variáveis limnológicas, de modo geral, revelaram diferenças na qualidade de água em relação às escalas espacial e temporal (efeitos de fatores climatológicos e hidrodinâmicos-vazão e tempo ) de retenção de água), com elevado aporte de nutrientes pelos rios Tietê e Piracicaba, além da incorporação, da sedimentação e da redução de materiais no reservatório de Barra Bonita, promovendo a melhoria da qualidade da água nos demais reservatórios, caracterizando assim, as primeiras estações como eutróficas e as demais como mesotróficas e oligotróficas. Concentrações de metais totais de água acima do limite estabelecido pela resolução CONAMA 20/1986 foram encontradas, bem como um aumento da fração biodisponível. Os ensaios revelaram toxicidade aguda para Dapnhia similis somente nos reservatórios localizados à justante da barragem de Barra Bonita, o que não seria inicialmente esperado. Tal fato pode estar relacionado às entradas difusas de poluição ou a presença de metais no sistema Tietê, os quais, no primeiro reservatório, estariam mais presentes na forma retida em função de sua maior incorporação (pela maior biomassa e pelo maior tempo de retenção), não causando toxicidade aguda aos organismos devido à parte dissolvida não ser tão elevada. Os resultados de toxicidade crônica, porém, configuraram um padrão diferente, verificando-se toxicidade em ordem decrescente (de Barra Bonita à Três Irmãos), na maioria dos períodos de amostragens, o que demonstra o estado de degradação ambiental nos reservatórios e a necessidade de estudos mais integrados para uma melhor avaliação ambiental.<br>Among the several impacts in the aquatic ecosystems, perhaps the construction of reservoirs represents one of the principal modifier agents, inserting physical, chemical and biological alterations in the systems before and after its construction. In Brazil, such impact is also singular, having verified this application for the construction of reservoirs, mainly the ones built in cascades (Paranapanema, Tietê and São Francisco system, for example) and, in that construction pattern, in most cases, a growing effect of the control of the quality of the water is anticipated, with the first reservoir being more eutrophic than the others for its capacity to retain materials that come from the principal tributary. In the southeast of São Paulo States, Barra Bonita, Bariri, Ibitinga, Promissão, Nova Avanhandava and Três Irmãos reservoirs stand out. Seeking to evaluate the impacts and contributing with information to evaluate the environmental conditions of those reservoirs, collections of water and sediment were accomplished in four different periods (October/99, February, May and July/00), in 15 sampling stations, including stations in the Tietê and Piracicaba Rivers and at the specified place after and before the line of the dam, from each one of the six reservoirs, as well as the Bauru River (a very impacted tributary of the Bariri Reservoir ). Toxicity bioassays were accomplished with samples of water and sediment using Daphnia similis (in acute toxicity bioassays) and Ceriodaphnia dubia (in chronic toxicity bioassays), analyses of total metals in the water and bioavailable in the sediment, besides the monitoring of limnological variables (temperature, pH, conductivity, dissolved oxygen, material in suspension, chlorophyll-a, total nutrients and dissolved). The results obtained for the limnological variables, in general, revealed differences in the quality of the water in relation to the spatial and temporary scales (effects of climatological factors and hydrodynamic- flowing out and residence time) with high contribution of nutrients from the Tietê and Piracicaba Rivers, besides the incorporation, the sedimentation and the reduction of materials in the Barra Bonita Reservoir, promoting the improvement of the water quality in the other reservoirs, characterizing, in this way, the first stations as eutrophic and the others as mesotrophic and oligotrophic. Concentrations of total metals in the water above the established limit for the resolution CONAMA 20/1986 were found out, and an increase of the fraction bioavailable of metals was verified as well. The bioassays only revealed acute toxicity for Daphnia similis to the points after the Barra Bonita Reservoir, something not initially awaited for. Such fact can be related to the diffuse entrances of pollution or to the presence of metals in the Tietê System, which, in the first reservoir, would be more present in the form retained in function of their largest incorporation (for the largest biomass and for the largest residence time), not causing acute toxicity to the organisms due to the dissolved part not to being so high. However, the results of chronic toxicity, configured a different partem, being verified toxicity in decreasing order (from Barra Bonita to Três Irmãos), during most of the samplings periods, which demonstrates the state of environmental degradation in the reservoirs and the need for more integrated studies for a better environmental evaluation.

A Temperatura de Superfície de Lago (TSL) consiste em um importante parâmetro limnológico na definição da qualidade de um corpo de água. Por meio da variação da TSL, uma série de parâmetros biológicos, físicos e químicos são modificados, no entanto, afetam, diretamente a sociedade, por meio dos diversos usos da água, do consumo doméstico ao agrícola e industrial. Os corpos de água estão diretamente relacionados a parâmetros meteorológicos e climáticos, dessa forma sofrem os efeitos das mudanças climáticas em escala global, mas, por outro lado, influenciam no ambiente local como amenizador climático, contribuindo com uma atmosfera local mais úmida. Dessa forma, o objetivo principal é analisar o comportamento da dinâmica da TSL do Guaíba, levando em consideração períodos de normalidade e anormalidade climáticas e as relações com agentes meteorológicos locais. Por meio da construção de perfis de temperatura e análises espaciais feitas sobre um arcabouço temporal de imagens termais dos satélites: Landsat 5 e 8/ e Terra (sensor MODIS) e suas respectivas relações com os fatores externos à massa de água do Guaíba (dados de meteorológicos, climáticos e topográficos locais). Dessa forma construiu-se um conjunto de dados detalhando a dinâmica da circulação e o comportamento espacial das temperaturas. Destaca-se que o Guaíba possui uma complexa dinâmica correlacionada com fatores atmosféricos globais e locais, mas de modo mais intenso com as variações meteorológicas locais em função da posição geográfica e da presença de uma sazonalidade bem definida, que propicia a entrada de frentes frias causando oscilações de temperatura e pluviosidade de modo muito marcante. Quanto aos períodos de normalidade e anormalidade climática, observase que durante os períodos de El Niño e La Niña há um aquecimento maior da TSL quando comparado com períodos de normalidade climática, sendo que o primeiro está mais relacionado ao aquecimento global da atmosfera; já, a segunda está relacionada à maior insolação em função do resfriamento da atmosfera, condicionando um céu limpo, ficando mais propício ao aquecimento por radiação solar.<br>The lake surface water temperature (LSWT) consists in an important limnological parameter in the quality definition of a body of water. Through the LSWT variation, a series of biological, physical and chemical parameters are modified, however they affect directly the society through the various water usage, from the domestic consumption to the agricultural and industrial. The bodies of water are directly related to the climatic and metereological parameters, this way they suffer the climatic change in a global scale, but, on the other hand, they influence in the local ambient as a climatic softener, contributing with a more humid local atmosphere. Thus, the aim of this paper is to analyze the dynamical behavior of Guaíba LSWT, whereas climatic normality and abnormality periods and their relations with local metereological agents. Through the profile of temperature and spatial analysis made over a temporal framework of the satellite thermal images: Landsat 5 and 8 and Terra (MODIS sensor) and their respective relations with the external factors in water mass of Guaíba (local topographic, climatic and metereological data). In this way a set of data were built detailing the circulation dynamic and the spatial behavior of the temperatures. Guaíba has a dynamic complex correlated with local and global atmospheric factors more intensely with the local metereological variation according to the geographical position and the presence of a huge seasonality, which allows the entrance of cold fronts causing rainfall and temperature oscilation in a remarkable way. In the normality and abnormality climatic periods, during El Niño and La Niña periods, there is a bigger LSWT warming if compared to normality climatic periods, being that the first one is more related with the atmosphere global warming, and the second one is related with the greater insolation due to the cooling of the atmosphere, conditioning a clean sky, becoming more conducive to solar radiation heating.

Made available in DSpace on 2014-06-11T19:30:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-01Bitstream added on 2014-06-13T21:01:13Z : No. of bitstreams: 1 henares_mnp_dr_jabo.pdf: 884278 bytes, checksum: 61b368c9033bf95a668c35d8757ed575 (MD5)<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Universidade Estadual Paulista (UNESP)<br>As alterações das características limnológicas do cultivo de Macrobrachium amazonicum com uso de substrato artificial e aeração noturna foram avaliadas em 12 viveiros (0,01 ha) de fundo natural povoados com 45 camarões m-2. O delineamento foi inteiramente casualizado com 4 tratamentos e 3 repetições. Os tratamentos foram: cultivo sem substrato artificial com aeração noturna (SSCA); cultivo com substrato artificial sem aeração noturna (CSSA); sem substrato e sem aeração noturna (SSSA); com substrato artificial com aeração noturna (CSCA). Nos viveiros dos cultivos CSSA e CSCA foram instaladas tela de nylon e nos viveiros dos cultivos SSCA e CSCA os aeradores foram acionados das 02h00 às 05h00. Mensalmente (janeiro a maio de 2009) foram determinados os valores de oxigênio dissolvido (OD), clorofila-a, turbidez, sólidos totais em suspensão (STS), nitrogênio Kjeldhal total (NKT) e fósforo total (PT). Os dados foram submetidos à ANOVA seguida do teste de Tukey (P<0,05). No final do experimento, a concentração de OD nos cultivos CSSA e SSSA foi em média 24,3% (5,9 mg L-1) menor em relação à concentração nos SSCA e CSCA (7,8 mg L-1). Os valores de clorofila-a, turbidez e STS foram maiores nos cultivos com aeração noturna. A concentração de NKT foi em média 20% maior nos cultivos SSCA e CSCA (1,2 mg L-1). Para PT, no final do experimento a concentração foi em média 2,9 vezes maior nos cultivos SSCA e CSSA (25,5 μg L-1) do que nos SSSA e CSCA (8,7 μg L-1). As alterações das características limnológicas foram mais intensas nos tratamentos com substrato artificial e aeração noturna, pois nesses cultivos os valores de clorofila-a, turbidez, STS, N e P foram mais elevados<br>The changes of limnological characteristics of Macrobrachium amazonicum shrimp-farm with artificial substrate and night aeration were evaluated in 12 grow-out ponds (0.01 ha) with 45 shrimps m-2. The completely randomized design was used with four treatments and three replications. The treatments were: rearing system without artificial substrate with night aeration (SSCA); system with artificial substrate without night aeration (CSSA); without artificial substrate without night aeration (SSSA) and rearing system with artificial substrate and night aeration (CSCA). In the CSSA and CSCA rearing ponds were installed nylon screen and in the SSCA and CSCA ponds rearing, the aerators were operated from 02h00 to 05h00. Monthly (from January to may 2009) were determined the dissolved oxygen (DO), chlorophyll-a, turbidity, total solids in suspension (TSS), total nitrogen Kjeldahl (TNK) and total phosphorus (TP). The datas were submitted to ANOVA followed by Tukey Test (P<0.05). In the end of experiment time, the DO concentration in the CSSA and SSSA was in average 24.3% (5.9 mg L-1) lower than SSCA and CSCA (7.8 mg L-1) concentration. The chlorophyll-a, turbidity and TSS values were higher in the night aeration rearing. TNK concentration was higher 20% (1.2 mg L-1) in the SSCA and CSCA systems. To TP, in the end of experiment the concentration was 2.9 times higher in the SSCA and CSCA (25.5 μg L-1) than SASA and CSCA systems (8.7 μg L-1). The changes of limnological characteristics were higher in with artificial substrate and night aeration treatments because in these rearing systems the chlorophyll-a, turbidity, TSS, N and P values were higher

As climatic conditions continue to change globally, there is a need to assess past environmental change in relation to changing water balance, temperature and sea-level. By understanding the extent of past environmental change, and how anthropogenic impacts have affected ecosystems, better and more accurate future predictions of change can be made. Through the use of the sedimentary record within coastal wetlands, geochemical, (organic content and stable isotopes) and biological (diatoms) proxies were utilised to determine; (i) the baseline water quality record for Soetendalsvlei, one of only a few coastal lakes in South Africa, (ii) the effect of agriculture and mouth manipulation of the Heuningnes Estuary on the microalgae ecology and (iii) the link between palaeo-salinity and trophic status on a regional basis between Soetendalsvlei and Groenvlei, situated 320 km apart. Present water quality and phytoplankton biomass and community structure were assessed for Soetendalsvlei and its associated wetlands, Voëlvlei and Waskraalsvlei to determine the current health of these systems and to obtain modern diatom analogues to be used in the palaeolimnological reconstruction of the coastal lake. Diatoms were not dominant during this study period. Chlorophytes and flagellates were the dominant phytoplankton groups throughout the different wetlands. With the exception of Voëlvlei, the wetlands were all in good health, although SRP concentrations were within the eutrophic to hypertrophic range and are cause for concern. In Voëlvlei, phytoplankton biomass was within the eutrophic range with chlorophyll a concentrations ranging between 20 – 400 ug.l-1 Cyanobacteria, a further indicator of eutrophic conditions, were dominant during the warmer summer periods. Rainfall and freshwater inflow had a significant effect on the biomass and composition of the phytoplankton and acted as a resetting mechanism for all the wetlands as water quality conditions improved thereafter. Comparisons of the water quality and phytoplankton community between the upper reaches of the Heuningnes Estuary and Soetendalsvlei, indicated that artificial breaching of the estuary mouth significantly impacted the connectivity between these two systems, with marine intrusion extending into the upper reaches, while freshwater conditions dominate in the coastal lake. Unfortunately for the palaeolimnological study diatom preservation was poor, however, geochemistry and stable isotope analyses did provide adequate evidence of marine transgression (~8000 yr BP and 4000-2000 yr BP) and regression events comparable to other South African sea-level models developed for the east and west coast. High organic matter content (i.e. higher trophic state) and estuarine POC (C4 vegetation) were associated with periods of marine regression, i.e. increased freshwater, whereas marine transgression events were associated with low organic content and marine POC and DOC. This is comparable to studies conducted in Uruguay (South America) where palaeo-salinity was related to trophic status, i.e. increased freshwater input was associated with high nutrients. Comparisons of the palaeo-record with recorded historical occurrences of droughts and floods, also provided a means of assessing the sedimentary record and to infer anthropogenic impacts after 1850 AD. Overall it can be concluded that coastal lakes of both continents in the Southern Hemisphere displayed similar trophic responses to sea-level fluctuations during the Holocene. This adds valuable information to global sea-level change models.

Powell and Sakinaw Lakes are stably stratified ex-fjords, which became isolated from the Strait of Georgia approximately 11000 years ago by emerged sills due to postglacial isostatic rebound. Although both lakes contain highly sulphidic relict seawater (Powell 3.0 mM; Sakinaw 5.5 mM), they have distinct chemical differences, which may be due to Sakinaw receiving occasional inputs of seawater over the barely-emerged sill when strong onshore winds are coincident with spring tides. Powell Lake, now 50 m above sea level, has not received additional seawater since the sill originally emerged. Sakinaw has a very sharp chemocline located just below the oxic/anoxic interface, whereas in Powell, the interface is spread out over 200 m of the water column. Although both lakes have freshened, the ratios of major ion concentrations relative to chloride in the bottom saline waters are similar to those of present-day seawater. There are some differences, however, and these can be explained, in part, by the difference in molecular diffusivities for each of the ions. The bottom waters of Powell and Sakinaw Lakes are chemically similar to anoxic sediment porewaters. containing high concentrations of nutrients, DOC and alkalinity. Unlike Sakinaw, however, Powell Lake has very low concentrations of phosphate in its bottom waters, in spite of both lakes having similar particulate organic N:P ratios in their upper oxic waters. This may be attributable to more recent addition of sulphate to Sakinaw, allowing greater mineralization of phosphorus compared to the relatively oxidant-starved Powell Lake. High concentrations of reduced iron, hydrogen sulphide, and polysulphides result in formation of iron monosulphides and pyrite in the anoxic water columns of both lakes. The presence of these two minerals correlates well with their calculated saturation states. Pyrite precipitates directly with no monosulphide precursor at depths where sulphide concentrations are low; thus monosulphide phases are undersaturated. As sulphide levels increase with depth, iron monosulphides become saturated and are detected in the water column. Pyrite can then form via the slower reaction of elemental sulphur with monosulphide. The large separation of the oxic/anoxic interface and the chemocline in Sakinaw (∼10 m) and especially in Powell Lake (∼100 m) relative to that of sediment pore waters allows excellent resolution of these processes.<br>Science, Faculty of<br>Earth, Ocean and Atmospheric Sciences, Department of<br>Graduate

The role of the materials coming from the watershed on the reservoir water quality is an emergent area of high scientific interest with many practical implications. In this study we investigated the influence of the materials coming from the Ter River watershed on the eutrophication process of Sau Reservoir, located in Barcelona (Spain).<br/><br/>First, we present a new methodology to calculate nutrient river loads, using fuzzy logic and tools from neural-networks optimization algorithms. The new method was more efficient and accurate than classical procedures.<br/><br/>Then, we demonstrate the effect of river materials (especially that of dissolved organic carbon) on the development of anoxic layers in the bottom layers of the reservoir. These results are not limited to Sau Reservoir, since other reservoirs in the world have shown the same responses. <br/><br/>The second part of the dissertation develops a watershed-scale model for the Ter River and the Sau Reservoir using HSPF. This included hydrology, river water temperature, and river total phosphorus concentration. Results were satisfactory, and the model implementation allowed testing state-of-the-art algorithms to calibrate complex models, based on the Bayesian statistical theory. On the other hand, different alternatives to model river water temperature were tested. Finally, we explored the possibility of using field data collected at the river reach scale, following the Nutrient Spiralling Concept, to parameterize the river total phosphorus model in the Ter watershed, with encouraging results.<br><I>CATALÀ:<br/><br/>L'efecte dels materials provinents de la conca de drenatge en la qualitat de l'aigua del embassaments és un àrea d'investigació amb considerable interès teòric i pràctic. En aquest estudi s'ha investigat la influència de les aportacions de la conca de drenatge del riu Ter en el procés d'eutrofització de l'embassament de Sau, a la província de Barcelona (Espanya). <br/><br/>Primer es detalla un nou mètode de càlcul de càrregues de nutrients en rius, fent servir la lògica difusa i eines provinents de l'optimització de xarxes neuronals. El nou mètode ha provat ser més eficient i precís que les alternatives clàssiques. <br/><br/>Després s'ha demostrat empíricament l'efecte dels materials provinents del riu (especialment del carboni orgànic dissolt) en la generació de capes anòxiques al fons de l'embassament. Aquest resultats no s'han aplicat només en el cas de l'embassament de Sau, sinó que han demostrat ser extrapolables a d'altres sistemes inundats de diferents llocs del planeta.<br/><br/>La segona part de la Tesi desenvolupa un model a escala de conca pel riu Ter i l'embassament de Sau amb HSPF, incloent hidrologia, la temperatura de l'aigua al riu, i la concentració de fòsfor total al riu. Els resultats han estat satisfactoris, i a més la implementació del model ha permès testar eines modernes de calibració de models complexos basades en l'estadística Bayesiana. Per altra banda, s'han testat diferents alternatives per a la modelització de la temperatura d'aigua en rius. Finalment, s'ha investigat la possibilitat de fer servir dades de camp recollides a escala de tram de riu, seguint el Nutrient Spiralling Concept, per a la parametrització del model de fòsfor total al riu Ter, amb resultats estimulants. </i>

Biomass of phytoplankton in large rivers may be maintained or even increased by inputs from hydraulic "dead zones". In some eutrophic rivers, dead zones can increase water retention time sufficiently for the development of algal concentrations substantially higher than in the main channel. "Seeding" of the main channel may then occur through the interchange of water between dead zones and the main channel. The objective of this thesis was to investigate the role of dead zones in the development of phytoplankton along the moderately eutrophic Rideau River. In the first chapter, I compare the suspended algal communities in dead zones and the adjacent main channel of the Rideau, to evaluate the assumption that dead zones support higher phytoplankton biomass. In the second chapter, I test the assumption that dead zones contribute algal biomass to the main channel of rivers. To do this, I examine the relationship between changes in main channel total chlorophyll a and the proportion of dead zone (inferred from the area of shallow macrophyte-dominated water) in 40 reaches along the Rideau, averaging approximately 2 km each. (Abstract shortened by UMI.)

Five different substrates (sand, fine gravel, coarse gravel, cobble and boulder) in nine streams forming a trophic gradient in the Ottawa Valley have been sampled in June 1992 to determine the effect of trophic level and substrate size on benthic communities. Total biomass of invertebrates (B, mg dry mass m$\sp{-2})$ and periphyton are strongly related to substrate particle size $(\Phi$, $-$Log$\sb2$diameter in mm) and trophy, represented by total phosphorus concentration (P, $\mu$g L$\sp{-1}).$ The model for periphyton biomass (Log$\sb $Peri = $-$0.08 $-$ 1.68Log$\sb $P + 1.08Log$\sb $P$\sp2\ -$0.13$\Phi\sp2)$ explains 67% of the observed variability and the model for invertebrate biomass (Log$\sb $B = 2.69 + 0.55Log$\sb $P + 0.3Log$\sb $Peri $-\ 0.01\Phi\sp2\ -$ 0.02Z) explains 68% of the observed variability (Peri = periphyton biomass in mgChla m$\sp{-2}$ and Z = depth in cm). The highest invertebrate biomass is observed on intermediate-size substrate (gravel) in phosphorus-rich streams. Periphyton biomass peaks on coarse substrates (boulder and cobbles) in streams where total phosphorus concentration is high $(>$50$\mu$gL$\sp{-1}).$ Individual body mass (W$\sb{\rm moy})$ is not affected by substrate size but is positively correlated with total phosphorus concentration (Log$\sb $W$\sb{\rm moy}$ = 1.67 $-$ 1.71Log$\sb $P + 0.96Log$\sb $P$\sp2,$ R$\sp2$ = 0.44). The effect of phosphorus and substrate on total biomass and mean individual body mass, are reflected in the size distribution of the invertebrates. Although the shape of the distribution is constant (unimodal), abundance of medium and large organisms increases in phosphorus-rich streams on intermediate-size substrates. A polynomial model including phosphorus concentration and substrate particle size is presented to quantify those variations of the size spectra. The predictions of this model are close to the observed values (R$\sp2$ = 0.89, residual mean square = 0.075) and this model could be very useful for a fast estimation of invertebrate size spectra.

Two studies on the effects of enhanced ultraviolet-B radiation (UVB; 280--320 nm) on planktonic organisms of Canadian High Arctic lakes are presented. In the first study, the long-term effects of a moderate increase in UVB levels on the planktonic community of a lake were evaluated using in situ mesocoms. Four mesocosms (3 m square and 3 m deep) were placed in Two Basin Lake, a small lake (14.2 ha) located on Ellesmere Island (79&deg;55.5'N, 84&deg;40'W; Nunavut, Canada). For 27 days, two mesocosms were exposed to full sunlight (including ambient UVB) while two others were exposed to sunlight plus artificially enhanced UVB. Chlorophyll a, zooplankton mean length and carbon allocation into macromolecular constituents were not affected by enhanced UVB. Phytoplankton productivity displayed diverse and inconsistent responses to enhanced UVB. Picocyanobacteria abundance decreased in the enhanced UVB mesocosms, but only at the surface. Enhanced UVB generally increased heterotrophic bacterial abundance and activity. Heterotrophic nanoflagellates and zooplankton abundances increased in the enhanced UVB treatment after 14 days. The cladocerans and rotifers were positively affected by UVB, while the copepods were negatively affected. The high levels (&ge; 5 mg L -1) of dissolved organic carbon (DOC) in this lake combined with vertical mixing generally protected the planktonic community from direct damage by enhanced UVB. It is hypothesized that UVB may have indirectly stimulated the microbial food web and the rest of the food chain through increased photodegradation of high molecular weight refractory dissolved organic matter into more bioavailable nutrients. In the second study, the short-term (2 to 24 h) effects of enhanced UVB on carbon uptake rates, photosynthetic fractionation into three size classes (picoplankton [0.2-2 mum], nanoplankton [2-20 [mum] and netplankton [> 20 mum]) and carbon assimilation into the four main end-products (low molecular weight metabolites [LMW], lipid, polysaccharide and protein) were assessed for nine lakes located near Resolute (74&deg;15'N, 94&deg;50'W) on Cornwallis Island (Nunavut, Canada). These lakes have low DOC levels (&le; 2 mg L-1). For each lake, 14C-inoculated water samples were exposed to 6, 25, 50 and/or 100% surface irradiance levels (E o) under natural solar radiation (including ambient UVB) or solar radiation plus artificially enhanced UVB. (Abstract shortened by UMI.)

Submerged macrophytes are known to influence the structure and function of lake ecosystems. Despite their importance, long term monitoring records of macrophytes are rare and thus relatively little is know regarding how human activities have altered macrophyte abundance in lakes. Paleolimnological reconstructions may provide the best approach for examining long-term trends in macrophyte abundance. This thesis evaluates the potential of sedimentary diatoms as indicators of macrophyte abundance and examines the long-term effects of human activities on ecosystem stability and macrophyte abundance. A novel analysis of an existing dataset showed that there were significant differences in the sedimentary diatom assemblage of lakes with either high or low macrophyte cover, and that these differences in the diatom assemblages can be used to infer the macrophyte cover of lakes. I further examined the influence of macrophytes on diatoms using a continuous measure of whole-lake macrophyte biomass in 41 lakes located in southern Quebec, Canada, and showed that diatoms can be used to detect substantial changes in macrophyte abundance through time. An analysis of the effects of external phosphorus (P) inputs to the lake showed that increasing P inputs resulted in greater diatom dissimilarity through time, providing empirical evidence for the idea that P inputs increase ecosystem variability. Finally, I show a widespread trend of a relative reduction in benthic diatoms and an inferred decline in macrophyte abundance between pre-1850 and present-day conditions, which is significantly related to modern land use. Together, this thesis advances our ability to track long-term changes in macrophyte abundance and demonstrates that human activities over the past ~150 years have altered ecosystem stability and reduced macrophyte abundance in southern Quebec lakes.<br>Les macrophytes submergées influencent la structure et les fonctions des écosystèmes lacustres. Étant donné que les programmes de surveillance à long terme (décennie ou plus) des macrophytes sont rares, l'impact des activités humaines sur l'abondance des macrophytes dans les lacs est relativement peu connu. La reconstruction paléolimnologique pourrait être la meilleure approche pour examiner les tendances à long terme de l'abondance des macrophytes. Cette thèse évalue le potentiel des diatomées sédimentaires comme indicateur de l'abondance des macrophytes et examine les effets à long terme des activités humaines sur la stabilité des écosystèmes et sur l'abondance des macrophytes. Une nouvelle analyse d'un jeu de donnée existant a montré qu'il y a une différence significative entre les assemblages des diatomées sédimentaires de lacs ayant de faibles ou de larges couvertures de macrophytes. Ces différences d'assemblage peuvent être utilisées afin d'inférer la couverture de macrophytes dans les lacs. Par la suite, j'ai examiné l'influence des macrophytes sur les diatomées en utilisant une mesure continue de la biomasse du lac total de macrophyte pour 41 lacs situés dans le sud du Québec, Canada. Cette étude a montré que les diatomées peuvent être utilisées pour détecter des changements substantiels dans l'abondance des macrophytes à travers le temps. Une analyse de l'effet des apports externes en phosphore (P) aux lacs a montré que l'augmentation des apports en P résulte en un accroissement de la dissimilarité des diatomées dans le temps, ce qui fourni une preuve empirique que les apports en P augmentent la variabilité des écosystèmes. Finalement, je montre la tendance répandue de la réduction relative des diatomées benthiques et le déclin inféré de l'abondance des macrophytes entre les conditions d'avant 1850 et de nos jours, ce qui est significativement relié à l'utilisation du territoire moderne. En résumé, cette thèse fournie une nouvelle méthode pour retracer les changements à long terme de l'abondance des macrophytes et démontre que les activités humaines des quelques 150 dernières années ont altéré la stabilité des écosystèmes et réduit l'abondance des macrophytes dans les lacs du Sud du Québec.

Past studies have shown that diffuse nutrient loading from agricultural activities is an important cause of lake eutrophication. The degree to which this relationship can be scaled-up (e.g. at an inter-regional scale) has not, however, been widely addressed. My thesis objectives were therefore to define the generality and the impact of agriculture land use and lake morphometry on lake water quality. Analyses along spatial and temporal scales were conducted to evaluate the significance of these effects. In the first manuscript, we tested whether agricultural activities explain a significant proportion of the variation in lake water quality at a broad inter-regional scale. The degree to which lake mean depth modulates this response was also assessed. From our meta-analyses of 358 lakes, we noted a significant correlation between total phosphorus concentration and the extent of agricultural catchment development. This relationship was further strengthened by including lake mean depth as a second predictor. We also observed among-study variability in the relationship between these three variables. Thus, although there is a general relationship between total phosphorus concentrations and our two predictors, agriculture catchment development and lake mean depth, regional baseline nutrient differences modify this relationship. To address the issue of lake morphometry more closely, we adopted a spatio-temporal approach to investigate whether the effect of agricultural catchment development on water quality differed between dimictic and polymictic Albertan lakes. We found that the correlation between surface water total phosphorus concentration and the percent of agriculture in a lake's catchment was strongly modified by lake mixis patt<br>Les études antécédentes ont démontré que les chargements de nutriment diffus parvenant d'activités agricoles sont une cause importante de l'eutrophisation des lacs. Par contre, le degré auquel cette relation peut être extrapolé à l'échelle interrégionale n'a pas été largement étudié. Ma thèse a pour but de définir la généralité et l'impact de l'usage des terres agricoles et la morphométrie des lacs sur la qualité d'eau. Des analyses selon des échelles spatiale et temporelle ont évalué la significativité de ces effets. Dans ce premier manuscrit, nous avons examiné si les activités agricoles pouvaient expliquer une proportion significative de la variation de la qualité de l'eau sur une vaste échelle interrégionale. Notre métaanalyse, basée sur des données parvenant de 358 lacs, a démontré une corrélation significative entre la concentration de phosphores totaux et le pourcentage de terres agricoles des basins versants. Cette corrélation a été améliorée en incluant la profondeur moyenne comme seconde variable prédictive. Nous avons aussi observé une variabilité parmi les études pour la relation entre ces trois variables. Donc, étant donné qu'il y a une relation générale entre la concentration de phosphores totaux et deux indices, le développement de l'agriculture des bassins versants et la profondeur moyenne des lacs, des différences de niveau de référence régionales modifie cette relation. Pour déterminer l'importance de la morphométrie des lacs plus en détaille, nous avons adopté une approche spatio-temporelle pour vérifier si les effets du développement de l'agriculture des bassins versants sur la qualité de l'eau sont différents entre les systèmes dimictiques et$

Despite the widespread use of chironomids in biomonitoring and paleoenvironmental research to infer environmental change, there is disagreement over the level of taxonomic resolution required for meaningful ecological interpretations. An objective of my thesis was to evaluate the differences in environmental inferences drawn at two different levels of taxonomic resolution. I found similar results between both levels of resolution with both live and sub-fossil datasets, but a number of taxa had different ecological preferences when examined at different resolutions. Another objective was to develop a chironomid-based training set, to identify the biotic and abiotic environmental variables that explain a significant amount of variation in the structure of surface sediment chironomid assemblages and to develop transfer functions for these environmental variables. Turbidity, dissolved inorganic carbon and drainage ratio were found to be the most influential environmental variables in our lake-set and robust transfer functions were developed for turbidity and chlorophyll a.<br>Les chironomides sont souvent utilisées dans la recherche paléo-environnementale des lacs pour reconstruire les changements environnementaux. Même si les chironomides sont utilisées largement comme indicateur biologique, il y a un désaccord concernant la résolution taxonomique utilisée pour obtenir des interprétations écologiques significatives. Le premier objectif de l'étude était de comparer les inférences environnementales obtenues d'analyses réalisées selon deux résolutions taxonomiques différentes; d'une part à résolution fine et d'autre part à résolution grossière. La majorité des résultats étaient similaires, cependant, quelques taxa avaient des préférences écologiques variées lorsqu'elles sont étudiées à des résolutions différentes. Le deuxième objectif était de calibrer les chironomides récupérées dans des sédiments de surface avec les variables environnementales de 26 lacs peu profonds dispersés dans le nord-est des États-Unis et de développer, lorsque possible, des modèles d'inférences. La turbidité, le taux de carbone non-organic dissous, et le ratio de drainage ont été identifiés comme les variables environnementales qui ont une grande influence sur la structure des communautés des chironomides dans nos lacs d'études.

Studies have revealed that upon recognition by cytotoxic T lymphocytes (CTL), apoptosis of the target cells is initiated by at least two distinct mechanisms; the Fas-Fas ligand (Fas-L) pathway, in which surface Fas-L on CTL cross-links Fas on target cells, and the granule exocytosis pathway whose major components consist of perforin, a putative pore-forming protein, and serine protease granzymes, particularly granzyme B (GrB). The DNA fragmentation into nucleosomal fragments is the most recognizable biochemical feature of apoptotic cell death that is regulated mainly by the DNA fragmentation factor (DFF) complex. DFF is composed of an inhibitor molecule (DFF-45/ICAD) tightly associated with a nuclease known as caspase-activated DNase (CAD/DFF-40/CPAN). Cleavage of the two caspase-3 specific sites on DFF45 during apoptosis was shown to result in the release of DFF-40 and the induction of DNA fragmentation. To investigate the ability of GrB to induce cell death in a caspase-independent fashion, we first analyzed the importance of putative caspase-3 cleavage sites within the DFF45 protein during apoptosis. In our study we provide direct evidence that the cleavage of DFF45 after aspartic acid 117 (D117) is both necessary and sufficient to induce DNA fragmentation through several apoptotic stimuli. Site directed mutation of D117E completely blocked oligonucleosomal DNA fragmentation without affecting other morphological and biochemical features of apoptotic cell death.<br>GrB shares with caspases the cleavage specificity for aspartic acid at the P1 cleavage site. Based on our observations that (i) GrB cleaves DFF45 at the same site that is necessary and sufficient for the induction of DNA fragmentation (D117) and (ii) DFF complex is constitutively localized in the nucleus, we next investigated the ability of GrB to induce DNA fragmentation in the absence of caspase activity. Using caspase-3 specific inhibitors, we show that GrB indeed can directly target DFF45 protein and induces DNA fragmentation. More importantly, we show the ability of GrB to directly cleave DFF45 and liberate CAD endonuclease activity. Taken together, these results revealed a new apoptotic pathway that provides a critical back-up system when the caspase pathway is inhibited in the target cells by viral or tumor proteins. (Abstract shortened by UMI.)

The toxin-producing potential of some freshwater cyanobacterial species and their ability to form dense blooms makes the possibility of an increase in their biomass of concern to lake managers and the general public. Modelling of cyanobacterial biomass and dominance in inland water bodies has demonstrated that cyanobacterial biomass increases concomitantly with nutrients in freshwater systems. Though temperature and water-column stratification are increasingly cited as factors promoting cyanobacterial biomass, support for this has been mainly provided by laboratory studies and individual lake studies. Furthermore it is not well known if models developed across large spatial gradients perform adequately at regional scales where responses could be modulated by additional unconsidered regionally-distinct variables. This thesis evaluates the effects of temperature, nutrients and other predictors on cyanobacterial biomass in North American lakes, through general models and when accounting for water body type and region of origin. A novel analysis of an existing dataset comprising single sample dates of over 1000 lakes in the United States showed that temperature was a significant predictor of cyanobacterial biomass. The effect of temperature was shown to be independent of those of nutrients and increases in total phytoplankton biomass. This suggests that warming alone might result in an increase in cyanobacterial biomass in lakes. The effects of the different variables varied between the lake systems considered (deep or shallow; natural lake or reservoir) with the strongest relationships found in deep natural lakes. An unpublished dataset of 88 Canadian lakes was used to test the effects of nutrients and temperature across regions using seasonally averaged data. These robust models provide some support for differing responses among regions, suggesting caution when applying general models to specific regions. Additionally, cyanobacterial genera biomass distribution in lakes was found to be explained by multiple environmental variables. Generally, nitrogen was found to be a significantly better predictor of cyanobacterial biomass than total phosphorus suggesting that nitrogen-fixation by cyanobacteria is less prevalent that previously estimated. Together, this thesis advances our understanding of the variables driving cyanobacterial biomass in lakes and demonstrates that under continued nutrient enrichment and warming temperatures increases in cyanobacterial biomasses in North American lakes could be expected.<br>Les proliférations de cyanobactéries sont des sujets de préoccupation à l'échelle globale en raison de leur capacité de former des écumes denses qui épuisent l'oxygène dissoute et qui peuvent produire des toxines, nuisant à l'utilisation des plans d'eau tant pour l'eau potable que les loisirs. La modélisation de la biomasse et de la dominance des cyanobactéries a préalablement démontré que leur abondance augmente de façon concomitante avec les nutriments dans les systèmes d'eau douce. Bien que la température et la stratification de la colonne d'eau soient de plus en plus citées comme facteurs favorisant la prolifération des cyanobactéries, ces associations sont surtout basées sur des études en laboratoire et de lacs individuels. En outre, il n'a pas été bien démontré que les modèles développés sur d'importants gradients spatiaux s'appliquent de façon adéquate à l'échelle régionale, où la biomasse pourrait aussi être modulée par des variables additionnels. Cette thèse évalue les effets de la température, des nutriments et d'autres prédicteurs sur la biomasse des cyanobactéries dans les lacs d'Amérique du Nord, à travers le développement de modèles général ainsi que des modèles tenant compte des spécificités régionales. Dans le premier chapitre, je présente une analyse exhaustive d'un ensemble de données de plus de 1000 lacs. Utilisant cet ensemble de données, où la plupart des lacs ont été échantillonnés une seule fois au cours de la saison de croissance, j'ai démontré que les concentrations de nutriments (azote et phosphore) et la température étaient des prédicteurs significatifs de la biomasse des cyanobactéries. L'effet de la température sur la biomasse des cyanobactéries est statistiquement indépendant de celui des nutriments. Ces résultats suggèrent que le réchauffement des eaux de surface pourrait entraîner une augmentation de la biomasse des cyanobactéries dans les lacs. Les effets des variables différaient entre les systèmes étudies (profonds, peu profond ; lac naturel, réservoir). Les meilleurs modèles ont été développés pour lacs naturels profonds. Dans le deuxième chapitre de cette thèse, j'ai examiné un ensemble de données inédites basées sur les moyennes saisonnières de 88 lacs provenant de trois régions du Canada (l'Alberta, la Colombie-Britannique et l'Ontario). J'ai développé des modèles prédictifs généraux et examiné comment les modèles pouvaient différer entre les régions en utilisant la modélisation linéaire générale et la modélisation à effets mixtes. Les prédicteurs environnementaux ressortant furent similaires à ceux du premier chapitre mais, tel qu'attendu, les modèles utilisant les moyennes saisonnières expliquèrent une plus grande proportion de la variance de la biomasse des cyanobactéries car elles sont plus représentatives. Ces modèles ont aussi relevé des différences claires entre l'Ontario et les autres provinces mais l'inclusion d'avantage de lacs de l'Ontario dans l'analyse serait nécessaire afin de résoudre pourquoi c'est le cas. Dans l'ensemble, cette thèse enrichit notre compréhension des variables influençant la prolifération des cyanobactéries dans les lacs. Elle démontre clairement que, par l'enrichissement continu en nutriments et le réchauffement des eaux de surface, une augmentation de la biomasse des cyanobactéries dans les lacs nord-américains serait attendue.

<p> In this dissertation, we explored three issues central to the understanding of the dynamics of the invasions of non-native crayfish. First, we investigated how the spread and abundance of non-native crayfish are influenced by biotic and abiotic factors, in the context of a river restoration project. Second, we tested whether roundtail chub, an Arizona native fish, demonstrate as much predatory pressure on invasive crayfish compared to small mouth bass, a non-native sports fish. Third, we investigated the consequences of crayfish spread by testing if crayfish reduce emerging aquatic insects. </p><p> In the first chapter, we examined the response of a spreading and invading non-indigenous crayfish population to a stream restoration project in travertine forming Fossil Creek, Arizona. We tested three predictions: 1) Increased flow would increase crayfish by providing more shallow riffles and backwater areas for juveniles. 2) Travertine deposition would decrease crayfish by cementing the substrate making it difficult for crayfish to burrow. 3) Changes in fish assemblage from non-native to native would reduce predation pressure on crayfish causing an increase in crayfish abundance. In contrast to our predictions there were no large increases in crayfish abundance following restoration. More detailed observations of different reaches, however, indicates that fish species and density exert some regulation over crayfish. Crayfish abundance decreased following restoration where exotic fish remain but slightly increased where they were removed. Additionally, areas in the river with increased travertine deposition had the largest declines following restoration. These observations suggest that crayfish abundance in this system is limited by substrate modification by travertine, to a lesser extent by predator regulation from fish, and interactions with flow. </p><p> In the second chapter, we compared the predatory effects of a native fish, roundtail chub (<i>Gila Robusta</i>), to the non-native, predatory smallmouth bass (<i>Micropterus dolomieu</i>) on the exotic northern crayfish (<i>Orconectes virilis</i>). The investigation occurred in Fossil Creek and addressed three questions: 1) Are native roundtail chub as effective predators on invasive juvenile crayfish as non-native smallmouth bass? 2) Will the removal of the bass have unexpected management implications due to increases in crayfish? 3) Is the benthic invertebrate community affected by differences in the assemblage of fish and crayfish? Two in-stream enclosure experiments tested the survival of juvenile crayfish in the presence of each of the two fish species with cage controls without fish. Crayfish abundance and benthic macroinvertebrates were compared between a section of the stream above a fish barrier where non-native species were removed to a section of stream directly below the barrier where they remained. The results of the enclosure experiments showed that non-native bass more strongly reduced juvenile crayfish than native roundtail chub. Crayfish abundance was also reduced in the stream reach containing bass compared to the reach composed of the native fish, despite similar environmental conditions. These results support the hypothesis that the native roundtail chub have reduced predatory pressure on crayfish abundance. Contrary to our predictions there were no significant differences in the benthic macroinvertebrate community suggesting that abiotic factors are more important than fish and crayfish in structuring this assemblage. </p><p> In the third chapter, we conducted two experiments using in stream enclosures to determine if the invasive crayfish <i>Orconectes virilis</i> in Arizona reduced the density and biomass of different groups of emerging aquatic insects. The two experiments occurred in different stream reaches that varied in geomorphic features and benthic community composition. One reach consisted of a riffle-pool morphology typical of many southwestern streams and an insect community composition dominated by dipterans. The other reach was characterized by travertine dam formation and a step-pool morphology with a more diverse benthic insect community. Crayfish had the greatest negative impact on the emergence density of mobile non-dipteran insect taxa and larger dipterans leading to declines in overall emergence biomass. Sedentary sediment dwelling taxa were relatively not impacted. We were not able to determine the exact mechanism of reductions but a disruption of insect colonization could have been due to either predation or dislodgement from the foraging activity of the crayfish. The large decline in biomass and a shift in insect emergence composition towards smaller bodied taxa rather than larger bodied taxa could have implications for insect predators in the riparian environment. Crayfish effects were not sensitive to reach differences in geomorphology or other environmental factors and were strikingly similar across both experiments. Relatively minimized impacts by high densities of crayfish indicated some type of density dependence or interference.</p>

Numerous authors are reporting that anthropogenic changes to the environment (i.e., cultural eutrophication and climate warming) have provided opportune conditions for a global dominance of phytoplankton communities by cyanobacteria. Yet, to date there has been no quantitative synthesis to support this claim and we have very little empirical evidence of synergistic relationships among the environmental drivers that could be responsible for an expansion of cyanobacteria through time. Multi-year lake monitoring data coupled with paleolimnological reconstructions proved to be an effective strategy to address these questions. In my doctoral thesis, I quantified temporal (decadal; 1985-2011 CE to centennial; 1800-2011 CE) cyanobacterial trends, both at the regional (Alberta, Canada) and global scale. Furthermore, to explain cyanobacterial trends observed in certain sites or time points, I evaluated additive and synergistic effects among drivers. For example, using phytoplankton time series data from five Albertan lakes, I show that the increase in cyanobacterial biomass is greatest under a combination of warmer water temperatures, increased intensity of thermal stratification, and elevated nutrient concentrations. I further show that space for time substitutions are valid for predicting cyanobacterial biomass by comparing empirical models developed from lake surveys to decadal-scale time series. To test whether the response of cyanobacteria in the face of environmental development has changed since the start of Anthropocene (ca. 1850 CE), I then compared models based on different time scales (decadal to centennial scales). In extending the timeframe, I found as much as a 70% loss in variance explained with the centennial models. At this regional scale, I showed that the anthropogenic changes that have taken place since ca. 1945 CE (eutrophication and warming of surface waters) have facilitated and explained the expansion of cyanobacteria. Finally, I quantified the increases in cyanobacterial abundance (rate and magnitude) over the past ~200 years by conducting a synthesis of more than 100 paleolimnological records and ~20 long-term monitoring records. With this dataset, I have shown that in the Northern Hemisphere, the increase in cyanobacteria is related to nutrient concentrations, lake elevation and lake morphometry. In general, my thesis has advanced our knowledge of the spatio-temporal dynamics of cyanobacteria in temperate lakes and the factors that can explain these dynamics. My thesis also helped isolate some of the causes of the accelerated expansion of cyanobacteria when environmental thresholds are crossed and when interactions amongst these drivers develop.<br>De nombreux auteurs suggèrent que les changements environnementaux d'origine anthropique (c.-à-d., eutrophisation et réchauffement climatique) ont créé des conditions propices pour une dominance globale des cyanobactéries dans les communautés phytoplanctoniques. Cependant, à ce jour, il n'existe pas de synthèse quantitative pour appuyer cette présomption et nous avons très peu d'évidences empiriques des relations synergétiques entre les facteurs environnementaux qui peuvent être responsables d'une expansion des cyanobactéries à travers le temps. Un échantillonnage pluriannuel des lacs, couplé avec des reconstitutions paléolimnologiques s'est avéré une stratégie efficace pour répondre à ces questions. Dans ma thèse de doctorat, j'ai quantifié les tendances temporelles (bi-décennale; 1985-2011 CE à centenaire; 1800-2011 CE) de cyanobactéries, aussi bien au niveau régional (Alberta, Canada) qu'au niveau mondial. De plus, afin d'expliquer les tendances de cyanobactéries observées dans certains sites ou points temporels, j'ai également évalué les effets additifs et synergétiques entre les facteurs environnementaux. Par exemple, en utilisant des suivis de données de phytoplancton à long terme, provenant de cinq lacs albertains, j'ai démontré que l'augmentation de la biomasse des cyanobactéries est due à l'effet additif de la hausse des températures d'eau, de l'intensification de la stratification thermique, et des concentrations de nutriments élevés. En comparant des modèles empiriques basés sur des données spatiales à des données temporelles, j'ai démontré que l'utilisation de données spatiales est une méthode valide pour prédire la biomasse des cyanobactéries à l'échelle décennale. J'ai ensuite comparé des modèles basés sur différentes échelles temporelles (bi-décennale à centenaire) pour vérifier si la réponse des cyanobactéries face aux développements environnementaux a changée depuis le début de l'Anthropocène (ca. 1850 CE). En prolongeant l'échelle temporelle, j'ai noté une perte de variance expliquée de plus de 70% chez les modèles centenaires. Au niveau régional, les changements anthropiques qui sont survenus depuis les années ca. 1945 CE (eutrophisation et augmentation de la température de l'eau) ont facilité et expliquent l'expansion des cyanobactéries. Finalement, j'ai quantifié l'augmentation de l'abondance des cyanobactéries (accélération et ampleur) au cours des dernières ~200 ans en menant une synthèse de plus de 100 archives paléolimnologiques et ~20 suivis de phytoplancton à long terme. Avec ces données, j'ai démontré que dans l'hémisphère nord, l'augmentation des cyanobactéries est reliée à l'augmentation de l'apport en nutriments, l'élévation et la morphométrie des lacs. En termes généraux, ma thèse a amélioré nos connaissances de la dynamique spatio-temporelle des cyanobactéries dans les lacs tempérés et des facteurs expliquant cette dynamique. Ma thèse a également permis d'isoler certaines causes de l'expansion accélérée des cyanobactéries lorsque des seuils environnementaux sont franchis et lorsque des interactions entre ces facteurs se développent.

Studies have been carried out on the phytoplankton of two freshwater lakes-eutrophic Rostherne Mere (Cheshire, UK) and mesotrophic Lake Glubokoe (Moscow region, Russia). Diversity was investigated in relation to two major aspects : (a) species composition, with indices of diversity being estimated from phytoplankton cell and colony counts, and (b) intraspecific diversity, looking at variation in elemental composition within selected species. The major genera of phytoplankton in Rostherne Mere included Stephanodiscus and Asterionella (spring diatom bloom), Chlamydomonas and Sphaerocystis (clear water phase), and a species assembly dominated by Microcystis (1997) or Ceratium (1999) in the late summer/autumn bloom. The sequence of major algal groups recorded at Lake Glubokoe were: chrysophytes, dinoflagellates and diatoms in spring, chlorophytes and blue-greens in the clear water phase, and an assembly of diatoms, blue-greens, dinoflagellates and chrysophytes in the late summer/autumn bloom. Indices of species diversity were determined in relation to species richness (Richness index, species count), general diversity (Shannon index) and species dominance (Simpson index). In both lakes, species richness and general diversity were greatest in the late summer bloom, a period of maximum phytoplankton stability and high productivity, characterised by K-selected species. Species dominance in Rostherne Mere was highest at extremes of productivity, including times of low algal biomass (clear water phase, 1997 and 1999) and very high biomass (late summer bloom, 1999). In Lake Glubokoe species dominance was maximal at the end of the summer/autumn bloom, a period of intermediate productivity and dominance of a limited number of species. Overall diversity (maximum seasonal Shannon index) decreased with increase in productivity, being highest in Lake Glubokoe (1998, low productivity), intermediate in Rostherne Mere 1997, and lowest in Rostherne Mere 1999 (highest chlorophyll-a levels). Phytoplankton diversity within the water column (mid-day) was determined at the key phases in lake stratification in Rostherne Mere (1999) and at the period of late summer bloom in Lake Glubokoe (1998). At each phase of the seasonal growth cycle, differences in the vertical distribution of individual species and algal groups reflected positioning of algae in relation to ambient conditions (nutrients, light, temperature, density gradients) or sedimentation within the water column. Phytoplankton diversity in species richness closely corresponded to the overall phytoplankton population (biomass profile and individual counts), usually having the maximum values in the epilimnion. Profiles of species dominance varied markedly in some of the depth analyses. High species dominance reflected either the growth of individual species (surface populations of chlorophytes in the clear water phase -Rostherne Mere) or the accumulation of populations at a particular depth due to sedimentation (hypolirrmion peak of diatoms in Lake Glubokoe). Phytoplankton statistical groups and assemblages were analysed within the water column of Rostherne Mere at the time of markedly high algal productivity (late summer bloom in 1999). Intraspecific diversity was examined on the basis of elemental composition of three main species (Ceratium hirundinella, Anabaena flos-aquae and Microcystis aeruginosa), sampled within the same water column in Rostherne Mere. The elemental composition of single cells within a mixed phytoplankton preparation was determined using Electron Probe X-ray Microanalysis. Intraspecific variation was investigated in relation to differences in elemental composition within the water column, variation within micropopulations, and pattern of elemental correlation. X-ray analysis detected a similar range of elements in the populations of Ceratium, Anabaena and Microcystis: magnesium, silicon, phosphorus, sulphur, chlorine, potassium, calcium, with P as the major anionic element, K as the major cation. Si was present at substantial levels. Elemental composition varied considerably within micropopulations of each species. Variation in the concentration of most elements was unimodal. Bimodal distribution was shown by K in Ceratium cells, and by Si in Anabaena and Microcystis cells, indicating particular subpopulations, within these species. Distinct subpopulations of high-Si and low-Si cells in Anabaena and Microcystis were attributed to the presence of Si as a surface layer associated with Al in high-Si cells. Low-K cells in Ceratium were seen as part of the population undergoing senescence. The pattern of elemental correlations revealed a major statistical association between Mg, P, S and K in each species throughout the water column. The XRMA results suggested an underlying homogeneity in the elemental composition of Ceratium, Anabaena and Microcystis within the top 8 m of the water column.

Orientador: Marcelo Luiz Martins Pompêo<br>Resumo: Reservatórios são ambientes artificiais destinados a multiplos usos e abrigam diferentes comunidades aquáticas. No entanto, apesar da importância desses ambientes aquáticos, os reservatórios são suscetíveis a inúmeros impactos como a eutrofização artificial e a contaminação por poluentes emergentes. Dentre as comunidades aquáticas, a comunidade zooplanctônica é composta por animais microscópicos que vivem em suspensão na água sendo que algumas espécies podem ser sensíveis ou tolerantes aos impactos antrópicos. Além de bioindicadores, a comunidade zooplanctônica é considerada um elo importante na teia trófica aquática. Diante disso, o presente estudo teve como objetivo principal utilizar o zooplâncton como bioindicador de qualidade ambiental em reservatórios do estado de São Paulo. Amostragens foram realizadas em sete reservatórios localizados em diferentes bacias hidrográficas durante 2015. Parâmetros físico-químicos foram medidos em cada local e foram coletadas amostras de água para determinação de variáveis limnológicas. Arrastos verticais foram realizados com rede de 68 m na zona eufótica para determinação da composição e abundância das espécies. Pode-se constatar que a maioria dos resevatórios apresentou condições eutróficas. Também pode-se verificar que algumas espécies estiveram associadas aos indicadores de eutrofização. Com intuito de contribuir na avaliação ambiental, foi desenvolvido um indíce preditivo de estado trófico baseado nos valores de tolerância de cada es... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: Reservoirs are artificial environments destinated for multilple purposes and home different aquatic communities. However, despite the importance of these aquatic environments, reservoirs are suscetible to numerous impacts such as artificial eutrophication and contamination by emerging pollutants. Among these aquatic biota, zooplanktonic communities are microscopic animals that live in suspension and some species may be sensitive or tolerant to anthropic impacts. Besides being bioindicators, the group is considered an important link between primary producers and upper trophic levels. In view of that, the main goal of the present study is to use zooplankton as an indicator of environmental quality in São Paulo state reservoirs. Samplings were carried out in seven reservoirs located in different hydrographic basins during 2015. Physical-chemical parameters were measured at each site and water samples were collected for determine limnological variables. Vertical hauls were carried out with a 68 m net at the limit of the euphotic zone for determine species abudance and composition. Through results, it can be verified that some species can serve as eutrophication indicators. Here, a predictive trophic status index based on zooplankton optimum values was developed. Significant correlations between the proposed metric and eutrophication indicators were detected. Finally, a functional diversity approach was used which in turn can be considered a useful tool in environmental monitorin... (Complete abstract click electronic access below)<br>Doutor

Els estanys freds i oligotròfics presenten una elevada diversitat d’organismes en el plàncton microbià, tant de protists com de procariotes. La coexistència d’aquesta elevada diversitat d’organismes i de formes de vida ha canviat la teoria ecològica. Les fluctuacions ambientals, i particularment el contrast entre estacions, esdevenen una oportunitat per a la coexistència. D’acord a aquesta idea, s’ha hipotetitzat que els enriquiments de nutrients episòdics juguen un paper fonamental pel manteniment de l’elevada diversitat microbiana, especialment perquè les aportacions de nutrients al llarg de l’any consisteixen en quantitats variables de diferents compostos de fòsfor i nitrogen, proporcionant una oportunitat per a la diferenciació de nínxols. S’han utilitzat dues aproximacions per a investigar la coexistència en el plàncton microbià: observacions regulars i manipulacions experimentals en el camp. La primera consisteix en el seguiment del bacterioplàncton al llarg d’un cicle anual en un llac que temporalment es congela i la segona, en un experiment in situ d’enriquiment de nutrients. Ambdues aproximacions s’han realitzat a l’Estany Redon, un estany d’alta muntanya ultraoligotròfic i profund que resta cobert per gel la meitat de l’any. En el Capítol 2, es descriuen els canvis estacionals observats en el bacterioplàncton. En els Capítols 3 i 4, s’investiguen les respostes específiques a l’enriquiment episòdic de nutrients en protists i bacteris, mitjançant tancats d’auto-ompliment i addicions de P i N. En el Capítol 2 es planteja un nou paradigma per explicar els canvis estacionals del bacterioplàncton en els llacs que estacionalment es glacen. En contraposició amb el tradicionalment assumit que els conjunts d’espècies es van substituint estacionalment, hi va haver un nucli d’espècies que es va desenvolupar principalment durant el període cobert de gel que era resistent i resilient a les elevades radiacions del període d’estiu. Un conjunt diferenciat es va desenvolupar per poc temps a l’epilimnion durant el període lliure de gel, treien avantatge de les condicions poc favorables pel conjunt d’espècies que trobarem a la columna d’aigua del llac durant la major part de l’any. L’experiment ENEX pretenia investigar la relació entre l’enriquiment episòdic de nutrients i la coexistència d’espècies. Pel que fa a la comunitat de protists (Capítol 3), el P va ser l’element limitant que va fomentar la competència entre espècies, mentre que el N va participar en mecanismes d’estabilització del nínxol. Moltes de les espècies que creixen en el llac en diferents moments de l’any es van recuperar durant l’experiment fet amb aigües epilimnètiques, demostrant que, encara que en abundàncies indetectables, les espècies tenen la capacitat de persistir en la columna d’aigua durant llargs períodes de temps i recuperar-se ràpidament des de les baixes densitats quan les condicions de nutrients els hi son favorables. Pel que fa al bacterioplàncton (Capítol 4), també es va donar un increment de biomassa a l’enriquir amb P. No obstant, en comparar-ho amb el cicle anual natural del llac es demostra que la resposta venia sobretot donada pel creixement del fitoplàncton i la major disponibilitat de carboni orgànic dissolt. Hi va haver poca segregació dels bacteris entre condicions de nutrients a un nivell taxonòmic alt (classe); no obstant, OTUs propers es van segregar al llarg del gradient de P i fonts de N indicant una diferenciació dels nínxols que pot promoure la coexistència. La tesi demostra el paper clau dels enriquiments episòdics de nutrients de composició variada per a mantenir una coexistència no-equilibrada estable a llarg termini en la comunitat planctònica microbiana.<br>Los lagos oligotróficos fríos contienen una gran diversidad de organismos microbianos planctónicos, protistas y procariotas. La coexistencia de una variedad tan grande de organismos y formas vivas ha desafiado la teoría ecológica. Las fluctuaciones ambientales, particularmente el contraste entre estaciones, se han señalado como una oportunidad para la convivencia. Como base de esta tesis, se planteó la hipótesis de que los enriquecimientos episódicos de nutrientes desempeñan un papel importante en el mantenimiento de una diversidad microbiana tan alta, particularmente porque las cargas de nutrientes durante todo el año consisten en diferentes cantidades y combinaciones de compuestos de fósforo y nitrógeno, lo que brinda una oportunidad para Diferenciación de nicho de nutrientes. Se utilizaron dos enfoques para investigar la coexistencia microbiana planctónica: observaciones regulares de campo y manipulaciones de campo experimentales. El primero involucró el monitoreo de un ciclo anual de la comunidad de bacterioplancton en un lago congelado estacionalmente y el segundo, un experimento de enriquecimiento de nutrientes in situ utilizando mesocosmos. Ambos enfoques se llevaron a cabo en el lago Redon, un lago ultraoligotrófico y profundo de alta montaña, que permanece cubierto de hielo durante aproximadamente medio año. En el Capítulo 2, se describen los cambios estacionales de la comunidad bacterioplanctónica. En los capítulos 3 y 4, se investigan las respuestas específicas de protistas y bacterias a los enriquecimientos episódicos de nutrientes utilizando mesocosmos de auto-llenado y adiciones de P y N. En el Capítulo 2 se sugiere un nuevo paradigma para los cambios estacionales de bacterioplancton en lagos cubiertos de hielo estacionalmente. En contraste con el reemplazo estacional del ensamblaje tradicionalmente asumido, existe un núcleo de ensamblajes de bacterioplancton que se desarrolla fundamentalmente durante el período cubierto de hielo, que es resistente o resistente a las condiciones de alta irradiación de la temporada de verano. Se desarrolla un ensamblaje diferente en el epilimnion durante la temporada libre de hielo durante un período corto, aprovechando la oportunidad de condiciones inadecuadas para los ensambles centrales que proliferan en la mayor parte de la columna de agua durante la mayor parte del año. El experimento ENEX tuvo como objetivo investigar la relación entre los enriquecimientos episódicos de nutrientes y la coexistencia de especies. Con respecto a la comunidad protista (Capítulo 3), P fue el nutriente limitante para las especies que fomentaba la competencia, mientras que N estuvo involucrado en mecanismos de estabilización de nicho. La mayoría de las especies que crecen en diferentes períodos del año se recuperaron durante el experimento de aguas epiliméticas, lo que demuestra que, aunque en abundancias indetectables, las especies tienen la capacidad de persistir durante largos períodos en la columna de agua y recuperarse rápidamente de bajas densidades cuando las condiciones son favorables y los nutrientes requeridos están presentes. Con respecto al bacterioplancton (Capítulo 4), también hubo un marcado aumento de la biomasa para el enriquecimiento de P. Sin embargo, la comparación con el ciclo natural del lago mostró que la mayor parte de la respuesta fue mediada por el crecimiento del fitoplancton y la mayor disponibilidad de carbono orgánico lábil. Hubo poca segregación en los altos rangos taxonómicos (es decir, clases) de las bacterias en condiciones de nutrientes; sin embargo, OTU de la misma familia se segregaron a través del gradiente P y las fuentes de forma N indicando una diferenciación de nicho que puede promover la convivencia. La tesis demuestra el papel clave de los enriquecimientos episódicos de nutrientes para mantener una coexistencia estable en desequilibrio en comunidades microbianas planctónica.<br>Cold, oligotrophic lakes hold a large diversity of planktonic microbial organisms, protists and prokaryotes. The coexistence of such a large variety of organisms and living forms has challenged the ecological theory. The environmental fluctuations, particularly the contrast between seasons, have been pointed as an opportunity for coexistence. As the bases of this thesis, it was hypothesized that episodic nutrient enrichments play a major role in the maintenance of such high microbial diversity, particularly because nutrient loadings throughout the year consist in different amounts and combinations of phosphorus and nitrogen compounds, providing an opportunity for nutrient niche differentiation. Two approaches were used to investigate the planktonic microbial coexistence: field regular observations and experimental field manipulations. The first involved the monitoring of one annual cycle of the bacterioplankton community in a seasonally frozen lake and the second, an in situ nutrient enrichment experiment using enclosures. Both approaches were carried out in Lake Redon, an ultraoligotrophic deep high mountain lake that is ice-covered for about half a year. In Chapter 2, the seasonal changes of the bacterioplankton community are described. In Chapter 3 and 4, the protist- and bacteria-specific responses to episodic nutrient enrichments are investigated using self-filling enclosures and P and N additions. A new paradigm for bacterioplankton seasonal changes in seasonally ice-covered lakes is suggested in Chapter 2. In contrast to the traditionally-assumed assemblage seasonal replacement, there is a core of bacterioplankton assemblages developing fundamentally during the ice-covered period, which is resistant or resilient to the high irradiances conditions of the summer season. A different assemblage develops in the epilimnion during the ice-free season for a short period, taking the opportunity of unsuitable conditions for the core assemblages that proliferate in most of the water column during most of the year. The ENEX experiment aimed to investigate the relationship between episodic nutrient enrichments and species coexistence. Concerning the protist community (Chapter 3), P was the limiting nutrient promoting species competition, while N was involved in niche stabilizing mechanisms. Most of the species typically growing at different periods of the year were recovered during the experiment from epilimnetic waters, showing that, although at undetectable abundances, species have the capacity to persist for long periods in the water column and quickly recover from low densities when favourable nutrient conditions are present. Concerning bacterioplankton (Chapter 4), there was also marked biomass increase to P enrichment. However, the comparison with the natural cycle in the lake showed that most of the response was mediated by the phytoplankton growth and the higher availability of labile organic carbon. There was little segregation at high taxonomic ranks (i.e., classes) of the bacteria across nutrient conditions; however, OTUs from the same family segregated across the P gradient and N form sources indicating niche differentiation that can promote coexistence. The thesis demonstrates the key role of episodic nutrient enrichments of varying composition for maintaining long-term stable non-equilibrium coexistence in the planktonic microbial community.

Considerando a importância da represa do Lobo, os indícios de eutrofização encontrados na área e tendo a recreação como seu principal uso, buscou-se, neste trabalho, avaliar a qualidade da água nos rios tributários e na represa, e sua adequação a balneabilidade. Para os afluentes do sistema, estimando-se, ainda, a contribuição dos mesmos ao aporte de materiais à represa, foram amostrados o córrego do Geraldo, a confluência dos córregos Água Branca e Limoeiro, o rio Itaqueri (antes da mineradora), o ribeirão do Lobo, o córrego das Perdizes, avaliando-se parâmetros físicos, químicos e biológicos da água e a vazão dos rios, em dois períodos (agosto/setembro e dezembro) de 2002. Os resultados, com base no índice de estado trófico, indicam que a maioria dos tributários, com exceção do córrego Água Branca (eutrófico), é oligotrófico. Na represa o estudo teve avaliações mensais para alguns parâmetros (nutrientes totais e dissolvidos, clorofila total e material em suspensão) e semanais para outros (pH, condutividade elétrica, temperatura da água, oxigênio dissolvido e coliformes fecais) ao longo de um ano (dezembro de 2001 a dezembro de 2002), em nove pontos, abrangendo a região de foz do rio Itaqueri, córrego do Geraldo e ribeirão do Lobo, quatro pontos distribuídos na praia do balneário Santo Antônio e um ponto a jusante da represa. A foz do rio Itaqueri apresentou-se meso-eutrófica no período, enquanto os outros pontos avaliados, oligotróficos. Apesar da condição favorável apresentada, a análise temporal dos dados (com estudos realizados nos últimos 30 anos), mostra uma evidente e preocupante alteração nas condições originárias desse sistema, indicando um evidente processo de eutrofização do reservatório, associado aos usos e ocupação da bacia hidrográfica (resíduos domiciliares, turismo, agricultura e pecuária). Em relação a balneabilidade os principais pontos de contaminação fecal na represa são as entradas dos tributários, enquanto o corpo da represa foi considerado excelente em todo o período amostrado. O córrego Água Branca, como corpo receptor do esgoto de Itirapina, é o mais comprometido dos corpos de água avaliados, além de ser o principal contribuinte de nutrientes e coliformes fecais para a represa do Lobo, através do rio Itaqueri.<br>Considering the importance of the Lobo reservoir, the sights of eutrophication found in the area and having recreation as its main usage, it has been tried, in the following paper, to evaluate the water quality in the tributary rivers and also in the reservoir as well as its adequacy to balneability. As main tributaries of the system, estimating yet their contribution to the input of materials to the reservoir, there have been sampled the Geraldo river, the meeting of Água Branca and Limoeiro rivers, the Itaqueri river (before the mining plant), the Lobo river, the Perdizes river, evaluating their physical, chemical and biological parameters and the rivers leakage during two different periods of time (August/September and December) from 2002. The results, which are based in the amount of trophic state, show that most of the tributaries, excepting the Água Branca river (eutrophic) are oligotrophic. In the reservoir, the evaluation has been more systematic, with monthly evaluations to some parameters (amount of total nutrients and dissolved nutrients, total chlorophyll and suspended material) and weekly evaluation to others (pH, electrical conductivity, water temperature, dissolved oxygen and fecal coliforms), during the period of one year (December, 2001 to December, 2002), in nine sites considering the region of the mouth of the rivers Itaqueri, Geraldo and Lobo, four sites along the beach of balneário Santo Antônio, and one site at the upper part of the reservoir. The mouth of the Itaqueri river has been meso-eutrophic throughout the period, while the other evaluated sites have been oligotrophic. In spite of the favorable condition showed by the IET, the timing analyses of the data (based on studies done in the last 30 years) shows a clear and worrying change in this system original conditions, related mainly to the increase of nutrients and its consequences, indicating a clear process of eutrophication of the system, what may be associated to the usages and occupation of the river basin (homes wasting material, tourism, agriculture and cattle-raising). Relating to balneability, the main sites of fecal contamination in the reservoir are the tributaries entrances (in the Itaqueri river the contamination happens due to Itirapina\'s sewer system), while the reservoir body has been considered excellent throughout all the sampled period. The Água Branca river, as receptor of the Sewer treatment station and also the sewer from two Itirapina\'s prisons, is the most risking one from the water bodies evaluated, besides being the main contributor of nutrients and fecal coliforms to the Lobo reservoir through the Itaqueri river.

A usina hidrelétrica Luis Eduardo Magalhães situada no Estado do Tocantins entre os municípios de Miracema do Tocantis e Lajeado é uma das maiores obras civis no país construída com recursos da iniciativa privada. A barragem apresenta 2.100 m de comprimento e vertedouros com 14 vãos e capacidade para escoar 49.870 m3/s de água. O reservatório encontra-se em área de cerrado com pouca fitomassa, baixo tempo de retenção (24 dias) e morfometria pouco complexa. A usina apresenta um circuito de geração com cinco casas de força e capacidade para abrigar cinco turbinas tipo Kaplan, com potência nominal de 170 MW e cinco grupos geradores de 190 MVA. Os estudos foram desenvolvidos no médio rio Tocantins na área de influência da UHE Lajeado (rio Tocantins e seus principais tributários) no período de fevereiro/99 a agosto/2001 e durante a fase de enchimento do reservatório, de setembro/01 a fevereiro de 2002, a partir da análise de 33 variáveis (temperatura do ar e da água; OD; transparência; turbidez; profundidade; cor; pH; condutividade; oxigênio consumido; DBO; cálcio, magnésio, sódio, potássio, cloreto, ferro total, dureza total, nitrato, nitrito, amônia, fosfato solúvel reativo, sílica reativa; alcalinidade total, sólidos em suspensão (totais, orgânicos e inorgânicos); fósforo total, nitrogênio total, coliformes totais, coliformes fecais, clorofila-a total, fitoplâncton e zooplâncton), além de perfis verticais na fase de enchimento, com o objetivo de caracterizar ecológica e limnologicamente o rio, bem como estudar as respostas das principais variáveis físicas, químicas e biológicas nos mecanismos básicos de funcionamento dos sistemas aquáticos da área, durante a construção da barragem e enchimento do reservatório, subsidiar os sistemas de suporte à decisão gerencial ligados à operação da usina, bem como o processo de educação e capacitação de recursos humanos. A estimativa da carga ) externa afluente ao reservatório baseou-se no modelo de Jorgensen & Vollenweider (1988), a partir das contribuições de nitrogênio e fósforo, com base nos dados de geologia e uso do solo da bacia, precipitação, efluentes domésticos e tributários. A carga interna foi obtida a partir das concentrações totais dos referidos nutrientes em função do volume do reservatório e a carga efluente foi obtida através das concentrações de jusante da barragem em função da vazão defluente. Os modelos adimensionais para as condições do reservatório na fase de enchimento foram calculados segundo; Imberger & Petterson, 1990; Leman et al, 1995 e Salençon & Thébaut, 1997. As análises indicaram diferenças na qualidade da água do rio Tocantins em relação aos seus tributários, tais como no pH, na alcalinidade total, na dureza total, na condutividade e na temperatura. O rio Tocantins apresentou-se como um rio de águas alcalinas, de elevada condutividade, com altos teores de cálcio e magnésio e grande diversidade planctônica, enquanto os tributários apresentaram-se mais ácidos, com baixa condutividade, elevadas concentrações de sódio, potássio e cloreto e temperatura mais baixa de suas águas, provavelmente devido a maior proteção ciliar. Na fase de enchimento os estudos demonstraram a formação de três compartimentos no reservatório, sendo dois deles C1 (Lajeado) e C2 (Palmas-Porto) estratificados termicamente e quimicamente, com formação de termoclimas resultantes do aquecimento térmico diurno. O terceiro compartimento - C3 a partir da região de montante da Ilha do Cachimbo, nas proximidades do ribeirão Conceição (Porto Nacional/Brejinho de Nazaré) é mais sujeito à ação do vento e comporta-se ainda como ambiente lótico. Durante esta fase a relação N:P apresentou variações acentuadas. O aumento de Ptotal é devido à decomposição da matéria orgânica afogada, da contribuição de fontes pontuais e não pontuais de resíduos domésticos e de outras origens, tais como abatedouros, criação de animais e diversas outras fontes. Como conseqüência do aumento do fósforo no reservatório, iniciou-se um processo de eutrofização, promovido também pela anoxia no fundo e pela redissolução do fósforo a partir da camada anóxica. Esse processo de eutrofização produziu florescimentos de Microcystis aeroginosa e Cylindrospermopsis raciborski. A aplicação dos números adimensionais na fase de enchimento mostrou que no reservatório da usina hidrelétrica do Lajeado, a ação do vento e o aquecimento térmico de superfície (radiação solar) são funções de força importantes na determinação dos mecanismos de funcionamento deste sistema determinando períodos de estabilidade e mistura que precisam ser monitorados. Os resultados sinalizam a necessidade de um gerenciamento integrado e preditivo como suporte às decisões técnico-administrativas. Do ponto de vista administrativo-gerencial o município de Palmas deverá trabalhar em parceria com os municípios de Lajeado e Porto Nacional e este último por sua vez, como o município de Brejinho de Nazaré, a partir dos Comitês Integrados de Bacia. Do ponto de vista ambiental, atenção especial deverá ser dada ao monitoramento de eutrofização e dos processos de estratificação em instalação nos compartimentos C1 e C2.<br>The Luis Eduardo Magalhães Hydroelectric Dam, located in Tocantins State between the municipalities of Miracema do Tocantins and Lajeado, is one of the largest constructions made with private funding in Brazil. The dam is 2,100 meters long with 14 spillways that have a discharge capacity of 49,870 m3/sec. The reservoir has a residence time of 24 days, a maximum depth of 35 m, and an average depth of 3 m. Five generating units with Kaplan turbines of nominal power of 170 MW and generators of 190 MVA compose the power station. This study was developed on the middle Tocantins River in the area of influence of the Lajeado UHE (Tocantins River and its tributaries) during the period ofFebruary 1999 to August 2001 and during the filling ofthe reservoir from September 2001 to February 2002. Thirty-three variables were measured: air and water temperatures, dissolved oxygen, transparency, turbidity, depth, color, pH, conductivity, oxygen deficit, biochemical oxygen demand, calcium, magnesium, sodium, potassium, chloride, total iron, total hardness, nitrate, nitrite, ammonia, reactive soluble phosphate, reactive silica, total alkalinity, suspended solids (total, organic and inorganic), total phosphorus, total nitrogen, total colliforms, fecal colliforms, phytoplankton, and zooplankton in vertical profiles. The objectives of this study were to characterize the ecology and limnology of the river/reservoir system and to study the physical, chemical, and biological responses of this system during the construction of the dam and the filling of the reservoir in order to provide information for decision-making linked to the operation of the hydroelectric project. Estimates of extemalloading of the reservoir were based on the model of Jorgensen and Vollenweider (1988) using nitrogen and phosphorus fluxes and data of geology, land use, rainfall, domestic effluents, and tributaries. The intemal loading was obtained from total concentrations of the above nutrients in function of the reservoir volume, and the outflow was determined by concentrations and discharge just downstream of the damo Non- dimensional models for the filling phase of the reservoir were calculated according to Imberger and Petterson (1990), Lerman et al., 1995, and Salençon and Thébault (1997). Water quality differed between the Tocantins River and its local tributaries. The Tocantins River has alkaline waters with high conductivity, high calcium and magnesium concentrations, high planktonic diversity, while its local tributaries are more acid with low conductivity and higher concentrations of sodium, potassium, and chloride. The temperatures of the tributaries are lower than that of the Tocantins River, probably due to proportionally greater forest cover along their margins. The filling of the reservoir produced three distinct limnological regions. Two of them, C 1 and C2, exhibit thermal and chemical stratification with the formation of diurnal thermoclines. The third region, C3, is located upstream of Cachimbo Island near Porto Nacional/Brejinho de Nazaré and is affected by wind action so that it still responds as a lotic environment. During the filling phase the N:P relationship varied greatly. Total P increased due to decomposition of submerged organic matter, point and non-point sources of domestic residues, such as sewage, slaughterhouses, animal raising. As a consequence of the P increase in the reservoir, eutrophication began, accelerated by anoxic bottom conditions, which promoted liberation of P from submerged soils. This eutrophication process produced blooms of Microcystis aeroginosa and Cylindrospermopsis raciborski. Non-dimensional analysis of the filling phase showed that wind and solar heading of surface waters are important forcing functions that control stratification and mixing regimes in the Reservoir. These results illustrate the necessity of integrated and predictive management of the reservoir. From an administrative perspective, the Municipality of Palmas should work with the Municipalities of Lajeado and Porto Nacional, and the latter with the Municipality of Brejinho de Nazaré via integrated basin committees. From an environrnental perspective, special attention should be given to monitoring eutrophication and stratification in sections C1 and C2 of the reservoir.

Submitted by Franciele Moreira (francielemoreyra@gmail.com) on 2018-07-03T13:40:43Z No. of bitstreams: 2 Tese - Isabel Rodrigues da Rocha - 2018.pdf: 13506861 bytes, checksum: 62a627a5358951b6c7a08e05e36e6b7e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-07-03T15:50:29Z (GMT) No. of bitstreams: 2 Tese - Isabel Rodrigues da Rocha - 2018.pdf: 13506861 bytes, checksum: 62a627a5358951b6c7a08e05e36e6b7e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Made available in DSpace on 2018-07-03T15:50:29Z (GMT). No. of bitstreams: 2 Tese - Isabel Rodrigues da Rocha - 2018.pdf: 13506861 bytes, checksum: 62a627a5358951b6c7a08e05e36e6b7e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-05-25<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>The development of mankind has always been connected to water resources. Currently, they have been more intensely exploited, especially in electrical power generation, through the opening of countless hydropower plants in Brazil from which many are found in the biome called Cerrado, due to its great water resources. From the need of studies on artificial reservoir once its made, the study on Salto do Rio Verdinho ́s river basin and waterpower plant ́s reservoir, located in the lower part of Verde river ́s river basin, close to Paranaíba river ́s downstream, tributary of Paraná river, was chosen. Verde river ́s flow is the verge of Caçu and Itarumã counties, in the south of Goiás state. Therefore, the main goal of this work is to comprehend the dynamics of usage and occupation of the river basin ́s lands and Salto do Rio Verdinho ́s waterpower plant relating to its water quality. With that in mind, the landscape was rated according to its physical features and the relation among its geology, soils, slope, geomorphology and remaining natural vegetation, based on the observation of the structural principle of the landscape, revealing that the environment of the river basin region belongs to Mesozoic era ́s geological formations, such as flattened relief and predominance of slope with very soft dissection between interfluves. Data on the changes in usage and occupation of the lands was possible through satellites images, where it was found that between 2005 and 2015, the main usage was pasture with 546 km2, the second, was areas intended to temporary cultures, with 237,4 km2. The analyses regarding the quality of the water from the reservoir, were made according to the resolution no 357 from 2005 of CONAMA, it was ranked as of very low quality due to its high percentage of nitrite and phosphorus. It was ranked as class 4. The variables: TDS and CE, Temp and TDS, Temp and CE, present significant correlations. The components optically active in the water (chlorophyll, concentration of suspended sediment, transparency and murkiness) that interfere in the electromagnetic spectra, present correlations with the measures of reflectance in the wavelength of 716 nm and 720 nm in January 2015, while the variables correlated better with the wavelength of 647 nm, 697 nm e 704 nm in February 2016, pointing that these wavelengths belong to the color red. The reflectance during the rainy months, January 2015 and February 2016, registered values between 0,04 and 0,23%, while in the dry season, July 2015 and August 2016, 0,03 and 0,14%. Generally speaking, that the research led to comprehend the current dynamics of the river basin environment and of the hydropower plant Salto do Rio Verdinho ́s reservoir, on their natural and man induced components that affect the water quality, thus, fulfilling the intended general aim.<br>O desenvolvimento da humanidade, sempre esteve ligado aos usos dos recursos hídricos. E na atualidade esses recursos, vem sendo explorado com mais intensidade, especialmente para a geração de energia elétrica, a partir da implantação de inúmeras hidrelétricas no Brasil e sobretudo muitas no Bioma Cerrado, que detém grande riqueza de recursos hídricos. Na perspectiva, de estudos necessários em ambiente de reservatório artificial após a sua implantação, o objeto do estudo selecionado foi a bacia hidrográfica e o reservatório da usina hidrelétrica (UHE) Salto do Rio Verdinho, localizada no trecho inferior da bacia hidrográfica do Rio Verde, próximo a jusante no Rio Paranaíba, afluente do Rio Paraná. Assim, o curso fluvial do Rio Verde é o limite territorial dos municípios de Caçu e Itarumã, no sul do estado de Goiás. Portanto, o presente trabalho teve por objetivo geral, compreender a dinâmica de uso e ocupação das terras da bacia e do reservatório da UHE Salto do Rio Verdinho em relação a qualidade das suas águas. Diante disso, foram realizadas avaliações da paisagem a partir da caracterização física e da relação dos seus atributos de geologia, solos, declividade, geomorfologia e remanescentes de vegetação natural, baseado na observação de princípio estrutural da paisagem, revelando que o ambiente da região da bacia como todo pertence a formações geológicas da Era Mesozoica, com relevos aplainados, e predomínio de declividades com dissecação muito fraca entre os interflúvios. As alterações no Uso e Ocupação das Terras, foram realizadas a partir de interpretação de imagens de satélites, onde se verificou que entre 2005 a 2015, o uso predominante são destinadas às áreas de pastagens com 546 km2, e a segunda classe de maior uso, foram de áreas destinadas para culturas temporárias com 237,4 km2. A análise da qualidade das águas do reservatório, foram realizadas segundo a Resolução no 357 de 2005 do CONAMA, sendo classificada como de péssima qualidade, devido aos elevados valores do nitrito e do fósforo nas águas do reservatório, que permitiram enquadra- las na classe 4. As variáveis TDS e CE, Temp e TDS, Temp e CE apresentaram correlações significativas. Os Componentes Oticamente Ativos (Clorofila, Concentração de Sedimentos em Suspensão, Transparência da água e Turbidez) na água que interferem nos espectros eletromagnéticos, apresentaram correlações com às medidas das reflectâncias nas faixas de 716 nm e 720 nm no mês de janeiro de 2015, enquanto que em fevereiro de 2016 as variáveis se correlacionaram melhores com as faixas de 647 nm, 697 nm e 704 nm, indicando que essas faixas compreendem ao comprimento de onda de luz vermelha. As reflectâncias dos meses chuvosos, de janeiro de 2015 e fevereiro de 2016, registraram valores entre 0,04 e 0,23%, já nos períodos secos registraram valores entre 0,03 e 0,14%, para os meses de julho de 2015 e agosto de 2016. De modo geral, a pesquisa, permitiu compreender a dinâmica atual do ambiente da bacia e do reservatório da UHE Salto do Rio Verdinho, sobre suas componentes naturais e antrópicas que afetam a qualidade das águas, assim, atingindo o objetivo geral proposto.

Submitted by FABIANA DA SILVA FRANÇA (fabiana21franca@gmail.com) on 2017-12-07T14:12:19Z No. of bitstreams: 1 ArquivoTotal.pdf: 5656794 bytes, checksum: cd6b716d0f23c645134652a09b9cddc7 (MD5)<br>Made available in DSpace on 2017-12-07T14:12:19Z (GMT). No. of bitstreams: 1 ArquivoTotal.pdf: 5656794 bytes, checksum: cd6b716d0f23c645134652a09b9cddc7 (MD5) Previous issue date: 2016-05-31<br>Zooplankton dynamics on a deep reservoir of Brazilian semiarid region: influence of weather, water quality an phytoplankton community. The semiarid region around the world are characterized by low rainfall, high temperatures throughout the year followed by long periods of drought, making them often temporary; it directly affects the quality of water and hence the diversity and abundance of organisms. Several aquatic systems in the semiarid region especially in Brazil, are shallow and so the planktonic studies were conducted at these sites. Thus, the present study aimed to analyze the dynamics of zooplankton in a deep dam in the northeastern semi-arid, and to observe the influence of environmental variables, phytoplankton community and seasonal climate on it. This study was conducted in four parts: the first was about the relationship between phytoplankton and zooplankton over two hydrological cycles. There was a predominance of cyanobacteria over all other phytoplankton groups, which resulted in low diversity zooplankton of the dam; rotifers were the most diverse and most abundant species during the rainy season; copepods were recorded throughout the collections in special juvenile stages; cladocerans had very low densities, and only appeared when environmental conditions have improved. Chapter 2 deals with the spatial differences in the distribution of zooplankton community and the influence of rainy and dry seasons on the distribution of these species; it was observed that the density of both planktonic groups were higher at the inlet, especially cyanobacteria and rotifers; microcrustaceans were especially abundant in the dry season; Chapter 3 analyzed the vertical distribution of zooplankton community and the influence of seasonality; what is observed is that while the rotifers shows a more homogeneous distribution while the microcrustaceans showed a typical distribution of vertical migration, especially in the dry season; Finally, Chapter 4 presents a simulation of artificial nutrient accumulation caused by the reduction of the water volume in case of prolonged drought; for that it were installed in the dam a bioassay mesocosm with tanks where treatment has been enriched with nutrients, nitrogen and phosphorus and the other served as a control. An unexpected result was the formation of a biofilm in periphyton treatment enriched with nutrients, which has the power of reducing the density of cyanobacteria, to the point of bringing the total transparency of the water at the end of the experiment; this suggests a breakdown of nutritional resources in the dam waters, due to the residence time of the water. The phytoplankton and zooplankton communities responds to this difference. The calanoid and cladocerans only appeared at the end of the study, namely the enriched treatments, while cyclopoids lowered their densities. From the study one can conclude that the difference in shallower environments, the deeper reservoirs shows an increased residence time of the water, which is reflected in the low zooplankton diversity, especially microcrustaceans and the occurrence of blooms of cyanobacteria; while shallow lakes show a concomitant ecological succession evolution of the hydrological cycle, reflecting a larger zooplankton diversity, the deeper reservoirs exhibit greater stability and that succession occurs is required higher rainfall regimes.<br>A dinâmica do zooplâncton em um reservatório profundo do semiárido brasileiro: influência do clima, da qualidade da água e da comunidade fitoplanctônica. As regiões semiáridas no mundo são caracterizado por poucas chuvas, altas temperaturas o ano todo, seguidos por longos períodos de estiagem, tornando-os muitas vezes temporários; isto afeta diretamente a qualidade das águas e, consequentemente a diversidade e abundância dos organismos ali presentes. A maioria dos sistemas aquáticos no semiárido, especialmente no Brasil, são rasos e por isso os estudos planctônicos foram conduzidos nesses locais. Diante disso, este trabalho teve por objetivo analisar a dinâmica do zooplâncton num açude profundo no semiárido nordestino, e observar a influência das variáveis ambientais, da comunidade fitoplanctônica e da sazonalidade do clima sobre ela. Este estudo foi conduzido em quatro partes: o primeiro foi sobre a relação entre fitoplanctônica e zooplanctônica ao longo de dois ciclos hidrológicas. Observou-se o predomínio das cianobactérias sobre todos os demais grupos fitoplanctônicos, o que refletiu na baixa diversidade zooplanctônica do açude; os rotíferos foram as espécies mais diversas e mais abundantes durante as chuvas; os copépodos foram registrados durante toda as coletas, em especiais os estágios juvenis; cladóceros apresentaram densidades baixíssimas, e só apareceram quando a condições do ambiente se tornaram menos eutrofizadas. O capítulo 2 tratou das diferenças espaciais na distribuição da comunidade zooplanctônica e a influência dos períodos chuvosos e seco sobre a distribuição desta comunidade; observou-se que a densidade de ambos os grupos planctônicos foram maiores na entrada, especialmente de cianobactérias e de rotíferos; os microcrustáceos foram especialmente mais abundantes na época seca; no capítulo 3 analisou-se a distribuição vertical da comunidade zooplanctônica e a influência da sazonalidade sobre esta; o que se observou é que enquanto os rotíferos tiveram um distribuição mais homogênea, os microcrustáceos apresentaram uma distribuição típica de migração vertical, especialmente na época seca; por fim, o capítulo 4 apresentou a simulação artificial do acúmulo de nutrientes provocada pela diminuição da do volume hídrico, no caso de uma seca prolongada; para isso foram instalados no açude um bioensaio em mesocosmo, com taques, onde um tratamento foi enriquecido com nutrientes, nitrogênio e fósforo e outro serviu como controle. Como resultado inesperado, ocorreu a formação de um biofilme de perifiton no tratamento enriquecido com nutrientes, que teve o poder de diminuir as densidades de cianobactérias, ao ponto de trazer transparência total da água no fim do experimento; isso sugere um esgotamento de recursos nutritivos nas águas do açude, devido ao tempo de residência da água. As comunidades fitoplanctônicas e zooplanctônicas responderam a essa diferença. Os calanóides e cladóceros só apareceram no fim do estudo, nos tratamentos enriquecidos, enquanto que os ciclopóides baixaram suas densidades. Com o estudo podemos concluir que à diferença dos ambientes mais rasos, o os açudes mais profundos apresentam um tempo maior de residência da água, que se reflete na baixa diversidade zooplanctônica, especialmente dos microcrustáceos e na ocorrência de blooms de cianobactérias; enquanto que os lagos rasos mostram um sucessão ecológica concomitante a evolução do ciclo hidrológico, refletindo uma maior diversidade zooplanctônica, os reservatórios mais profundos exibem uma estabilidade maior e para que essa sucessão ocorra é necessário maiores regimes pluviométrico.

Orientador: Antonio Fernando Monteiro Camargo<br>Banca: Irineu Bianchini Júnior<br>Banca: Lúcia Maria Carareto Alves<br>Banca: Wagner Cotroni Valenti<br>Banca: Sidnei Magela Thomaz<br>Resumo: As alterações das características limnológicas do cultivo de Macrobrachium amazonicum com uso de substrato artificial e aeração noturna foram avaliadas em 12 viveiros (0,01 ha) de fundo natural povoados com 45 camarões m-2. O delineamento foi inteiramente casualizado com 4 tratamentos e 3 repetições. Os tratamentos foram: cultivo sem substrato artificial com aeração noturna (SSCA); cultivo com substrato artificial sem aeração noturna (CSSA); sem substrato e sem aeração noturna (SSSA); com substrato artificial com aeração noturna (CSCA). Nos viveiros dos cultivos CSSA e CSCA foram instaladas tela de nylon e nos viveiros dos cultivos SSCA e CSCA os aeradores foram acionados das 02h00 às 05h00. Mensalmente (janeiro a maio de 2009) foram determinados os valores de oxigênio dissolvido (OD), clorofila-a, turbidez, sólidos totais em suspensão (STS), nitrogênio Kjeldhal total (NKT) e fósforo total (PT). Os dados foram submetidos à ANOVA seguida do teste de Tukey (P<0,05). No final do experimento, a concentração de OD nos cultivos CSSA e SSSA foi em média 24,3% (5,9 mg L-1) menor em relação à concentração nos SSCA e CSCA (7,8 mg L-1). Os valores de clorofila-a, turbidez e STS foram maiores nos cultivos com aeração noturna. A concentração de NKT foi em média 20% maior nos cultivos SSCA e CSCA (1,2 mg L-1). Para PT, no final do experimento a concentração foi em média 2,9 vezes maior nos cultivos SSCA e CSSA (25,5 μg L-1) do que nos SSSA e CSCA (8,7 μg L-1). As alterações das características limnológicas foram mais intensas nos tratamentos com substrato artificial e aeração noturna, pois nesses cultivos os valores de clorofila-a, turbidez, STS, N e P foram mais elevados<br>Abstract: The changes of limnological characteristics of Macrobrachium amazonicum shrimp-farm with artificial substrate and night aeration were evaluated in 12 grow-out ponds (0.01 ha) with 45 shrimps m-2. The completely randomized design was used with four treatments and three replications. The treatments were: rearing system without artificial substrate with night aeration (SSCA); system with artificial substrate without night aeration (CSSA); without artificial substrate without night aeration (SSSA) and rearing system with artificial substrate and night aeration (CSCA). In the CSSA and CSCA rearing ponds were installed nylon screen and in the SSCA and CSCA ponds rearing, the aerators were operated from 02h00 to 05h00. Monthly (from January to may 2009) were determined the dissolved oxygen (DO), chlorophyll-a, turbidity, total solids in suspension (TSS), total nitrogen Kjeldahl (TNK) and total phosphorus (TP). The datas were submitted to ANOVA followed by Tukey Test (P<0.05). In the end of experiment time, the DO concentration in the CSSA and SSSA was in average 24.3% (5.9 mg L-1) lower than SSCA and CSCA (7.8 mg L-1) concentration. The chlorophyll-a, turbidity and TSS values were higher in the night aeration rearing. TNK concentration was higher 20% (1.2 mg L-1) in the SSCA and CSCA systems. To TP, in the end of experiment the concentration was 2.9 times higher in the SSCA and CSCA (25.5 μg L-1) than SASA and CSCA systems (8.7 μg L-1). The changes of limnological characteristics were higher in with artificial substrate and night aeration treatments because in these rearing systems the chlorophyll-a, turbidity, TSS, N and P values were higher<br>Doutor

Photodegradation rates of methylmercury (MeHg) were measured in water samples from several lakes in the Lake Berthelot region in Quebec in order to investigate the impact of drainage basin logging and associated changes in dissolved organic carbon (DOC) concentrations on MeHg levels in lake water. The lakes were selected on the basis of the amount of logging that had previously taken place in the drainage basin, and on DOC levels which were correspondingly higher in logged lakes due to increased runoff. Lakes DA9 and DF9 had DOC concentrations of 12.3 and 20.9 ppm, respectively and were designated as high DOC for the purposes of this study. Lakes N55 and N70 had DOC concentrations of 6.9 and 6.8 ppm, respectively and were designated as low DOC lakes. Experiments were conducted with both ambient and 2 ppt spiked MeHg levels in the high and low DOC lakes to determine whether the spiked levels reflect photodegradation patterns occurring in nature. The effect of different sized DOC fractions on photodegradation rates were also examined. Upon spiking, the binding of added MeHg reached equilibrium virtually immediately (within minutes) for all size fractions. It was hypothesized that less photodegradation of MeHg would be found in high DOC lakes than in low DOC lakes. In contrast to expected results, no photodegradation was observed in the two lower DOC lakes, but there was photodegradation in the two higher DOC lakes. Hypothesizing that larger size fractions of DOC would result in lower methylmercury (MeHg) photodegradation rates, water samples were fractionated into three DOC size fractions (300 kDa, 30 kDa, and 5 kDa). In the two high DOC lakes in which photodegradation was detected, DOC size fractions had an effect on photodegradation rates, though this effect varied. Average k values (hr-1) for DA9 were -1.25 x 10-1 for the 5 kDa fraction, -1.16 x 10 -1 for the 30 kDa fraction, and -9.21 x 10-2 for the 300 kDa fraction, indicating a decrease in photodegradation rates with larger fractions. For DF9, average k values were -1.69 x 10-1 for the 5 kDa fraction, -6.38 x 10-2 for the 30 kDa fraction, and -1.34 x 10-1 for the 300 kDa fraction, which does not indicate a clear trend in photodegradation rates with respect to DOC size fraction. A comparison of samples from a wetland outflow using ambient MeHg levels demonstrated that 300 kDa DOC fractions showed no photodegradation while 5 kDa DOC showed photodegradation with a k value of -9.12 x 10-2 (hr-1). Overall, watershed logging status was found not to affect MeHg photodegradation rates in the lakes studied. A possible contributor to the variation in photodegradation rates between lakes was postulated to be pH, with H+ ions displacing MeHg from binding sites on DOC and rendering it available for photodegradation. To study the relationship between rates of photodegradation and pH, water samples were adjusted to pH values of approximately 4.5, 6.5, and 7.5 and incubated in sunlight. Rates of photodegradation increased with decreasing pH conditions in all lakes, except for one lake (N55) which also had no detectable photodegradation during the initial field trials. In the remaining three lakes studied, however, lower pH values (4.1-4.6) resulted in greater photodegradation than higher pH values that resulted in little or no photodegradation. It appears that this effect only occurs in lakes with a potential for photodegradation. As results suggested that the size of DOC controls rates of photodegradation, samples were analyzed for the size of DOC and corresponding MeHg content using tangential flow ultrafiltration (TFUF). The efficacy of the TFUF system as a means of both removing microbes as well as fractionating DOC into differing size fractions was evaluated. Results indicated that this is an effective field-portable method. Mass balances for MeHg recovery after filtering large volumes of water were found to be 96% for the 5 kDa filter, 81% for the 30 kDa filter, and 109% for the 300 kDa filter, while flow rates decreased by 26%, 17%, and 50% respectively. Potential artifacts of DOC fractionation using the TFUF were investigated. The amount of DOC passing through the filter was found to decrease with increasing volume of filtrate that passed through the membrane.

The microbial metacommunity of the Pyrenees mountain range has never been studied at the regional level. In this PhD thesis, the main goal is to describe the taxonomic diversity and reveal the ecological processes (biotic and abiotic) behind the spatial distribution and heterogeneity of surface communities of alpine lakes. With a sampling of more than 300 lakes during summer of 2011 and high-througput sequencing of ribosomal markers (16S and 18S rRNA), we analized the microbial profiles of archaeal, bacterial and eukaryotic communities. We highlighted the discovery and description of novel and unknown lineages such as Pacearchaeota or Woesearchaeota (Archaea) or Chytridiomycota (Eukarya). We analyzed the role of environmental filtering and dispersal processes, as well as potential species interactions as drivers of local community assemblages<br>La metacomunidad microbiana de Pirineos nunca ha sido estudiada a nivel de región completa. En esta tesis se busca describir la diversidad taxonómica y revelar los procesos ecológicos (bióticos y abióticos) que pueden estar tras la distribución espacial y la heterogeneidad de las comunidades superficiales de lagos alpinos. Mediante un muestreo de más de 300 lagos durante el verano de 2011 y técnicas de secuenciación masiva de genes ribosómicos (16S y 18S rRNA) se obtuvieron los perfiles microbianos de comunidades de arqueas, bacterias y eucariotas. Se puso énfasis en el descubrimiento y descripción de linajes nóveles y desconocidos como Pacearchaeota o Woesearchaeota (Archaea) o Chytridiomycota (Eukarya). Se analizan el filtro ambiental y procesos de dispersión, así como las interacciones potenciales entre especies como responsables del ensamblaje de las comunidades locales

Os reservatórios de água são sistemas artificiais rasos destinados à múltiplos usos. Estes usos associados as atividades desenvolvidas na bacia hidrográfica acarretam impactos nos corpos d\'água, principalmente nos sedimentos, os quais representam um depósito e também uma fonte de contaminantes sobre determinadas condições ambientais. O tipo de construção dos reservatórios é bastante relevante no contexto de poluição e contaminação. Teoricamente os reservatórios construídos em cascata tendem a apresentar uma melhora na qualidade das águas e sedimentos ao longo da construção, pois o reservatório acima retém parte dos poluentes e contaminantes que entrariam no reservatório subsequente. Para avaliar a qualidade dos seis reservatórios construídos em cascata no rio Tietê (SP), foram realizadas quatro coletas (outubro/99, fevereiro/00, maio/00 e julho/00) nas quais foram amostradas água e sedimento para realização de análises físicas, química , biológica e ecotoxicológica, em 15 pontos deste sistema. Os resultados em geral demonstraram uma melhoria nas condições físicas e químicas da água, sedimento e da toxicidade (% de mortalidade) nos últimos reservatórios (Nova Avanhandava e Três Irmãos), sendo que os rios Piracicaba e Tietê apresentaram as piores condições ambientais. A toxicidade variou com o período de coleta, sendo que as maiores porcentagens de mortalidade ocorreram em outubro/99 e as menores em maio/00. As análises histológicas realizadas com organismos expostos aos sedimentos coletados em fevereiro, confirmaram alterações branquiais de primeiro grau em sete dias de exposição. As análises químicas das águas extraídas dos bioensaios em maio/00 também demonstraram a presença de nutrientes e metais em concentrações elevadas, confirmando então a importância dos sedimentos como liberadores de poluentes para a coluna de água, prejudicando os organismos de coluna de água.<br>Water reservoirs are shallow artificial systems which can be constructed for many purposes. The use of these reservoirs and the different activities developed in the hydrographic basin, can result in alterations in these border water, mainly in the sediments, which represent a storage and a contaminant source under specific ambient conditions. The position of the reservoir along the river is very significant in relation to pollution and contamination. Cascade reservoirs are prone to raise the water and sediment quality downstream, because contaminants and pollution are retained in the upstream reservoirs. In order to assess the water and sediment quality in six Tietê river cascade reservoirs, we realized chemical, physical, biological and ecotoxicological analysis in 15 locations. Samples were collected in October/1999, February, May and July/2000. The overall results showed that water and sediments physical and chemical conditions, as well as the toxicity (% mortality), were improved in direction to the last reservoirs (Nova Avanhandava e Três Irmãos). Piracicaba and Tietê rivers presented the worst ambient conditions. The toxicity presented seasonal variation, in the manner that higher mortality percentage occurred in October and the lower in May. Hystological analysis of text organism exposed to sediments collected in February showed branchial alterations after seven days. Chemical analysis of the water used in the bioassays showed high metal and nutrients concentrations in May, suggesting the importance of these sediments, since they are able to release pollutants to the water column.

A represa Ponte Nova constitui, juntamente com as represas Jundiaí Taiaçupeba, Paraitinga e Biritiba-Mirim, o Sistema Produtor Alto Tietê, da SABESP, responsável pelo abastecimento de água de parte da Região Metropolitana de São Paulo. O presente trabalho teve por objetivos verificar o comportamento espacial e temporal de variáveis limnológicas do reservatório, identificar o seu grau de trofia e fazer considerações a respeito do seu manejo visando contribuir para a conservação desse ambiente. O trabalho de campo foi realizado ao longo de um período de 12 meses, através de coletas mensais de amostras de água em estações de coletas no reservatório, estabelecidas segundo a sua morfometria e também na entrada de seus principais tributários, Rio Tietê e Rio Claro e a jusante da barragem. Foram determinadas variáveis físicas e químicas da água e também a concentração de pigmentos totais em diferentes profundidades ao longo do perfil vertical das estações do reservatório e na água sub-superficial dos tributários e no Rio Tietê a jusante da represa. Os resultados mostraram características típicas de reservatório oligotrófico, como baixa concentração de pigmentos e de nutrientes e alta transparência. Por outro lado o reservatório apresentou um período de estratificação térmica e química bem definidas, com grande estabilidade, apesar do tempo de residência reduzido, característica essa de ambientes eutrofizados, com alta demanda de consumo de oxigênio nas águas mais profundas. A compartimentação espacial observada, tanto ao longo do eixo longitudinal da represa quanto do eixo transversal no local de maior largura, foi determinada principalmente pela profundidade e pela entrada dos tributários. Os dados de jusante indicam concentrações de nutrientes e de material em suspensão de modo geral inferiores àquelas registradas nos principais tributários, indicando uma retenção eficiente da carga afluente ao reservatório, apesar de não existirem, na bacia, influências antrópicas significativas sobre os corpos d?água. A operação do reservatório influencia de forma significativa seu comportamento limnológico e algumas considerações a esse respeito foram feitas.<br>Ponte Nova Reservoir is a component of SABESP?s Sistema Produtor Alto Tietê, with Jundiaí Taiaçupeba, Paraitinga e Biritiba-Mirim reservoirs. The system is responsible for the water supply of part of the Região Metropolitana de São Paulo. The aim of the present study was to verify the reservoir spatial and temporal behavior of the limnological variables, to establish its trophic conditions, and to make assessments concerning the management in order to contribute to the conservation of this environment. The field work of this project was undertaken during a period of 12 months, where monthly water samples were collected in stations established in the reservoir according to its morphometry, the entry of the main tributaries, Tietê and Claro rivers, and downstream the dam. Physical and chemical variables of the water and the concentration of total pigments in different depths along the vertical profile of the studied stations were determined, as well as of the water of the subsurface of tributaries and downstream of the dam. The obtained data was characteristic of an oligotrophic reservoir, as low concentrations of pigments and nutrients, and high transparency. In the other hand, the reservoir presented a well defined thermal and chemical stratiphication period, with great stability, in spite of the reduced residence time, characteristic of eutrophic environments, with high oxygen consumption demand in deeper waters. The observed spatial compartimentation, both along the longitudinal axis and the transversal axis at the maximum width, was determined mainly by the depth and by the entry of tributaries. The nutrient and suspended solids concentrations registered downstream were generally inferior to those registered at the main tributaries, indicating an efficient retention of the affluent (ou input) load to the reservoir, in spite of the inexistence of significative anthropogenic influences in the watershed. The reservoir management greatly influences its limnological behavior, and considerations concerning this matter were evaluated.