Rainfed areas in the Dry-Zone of Sri Lanka are characteristic of extensive marginal agro-ecosystems known as the semi-arid tropics (SAT) populated by poor farming communities. In the Dry-Zone and elsewhere, the traditional response to seasonal water scarcity was to construct rainfall-harvesting devices known as ‘tanks’; created by building earthen dykes across ephemeral streams in undulating terrain. Most are held in common ownership by adjacent communities, who use them for multiple functions including irrigation, bathing and fishing. Storage efficiency is enhanced by arranging tanks in cascading sequence within watersheds so that drainage waters can be re-used. The aim of this study was to evolve improved collective strategies for the management of seasonal water bodies (focussing on aquatic production) in order to reduce the vulnerability of the poorest groups. Understanding of these complex systems requires a holistic approach which integrates hydrological, biological and socio-economic factors on a suitable (watershed) scale. Work commenced with a comprehensive situation analysis, culminating with the formulation of a participatory research agenda for action research based on low-input stocking enhancements. Village livelihoods have traditionally revolved around paddy cultivation as the primary tank function; however, in recent times, water-use strategies have responded to a range of demographic, economic and environmental pressures with implications for the sustainable management of natural resources, especially living aquatic organisms. Natural fish production in the most seasonal tanks relies on intermittent spill-events which link successive tanks; these provide migration routes which permit recruitment of stocks from lower perennial tanks. Rehabilitation initiatives that increase the storage / irrigation capacity of tanks or poorly designed surplus weirs that impede migration have negative impacts on fisheries, though they are rarely considered by planners. The fundamental concept of the purana complex (PC) as the smallest logical sub-component of the watershed for intervention is introduced. Within PC boundaries discrete community groups bound by ties of kinship and caste, control access to private and commonly held natural resources. PCs in the uppermost reaches of watersheds are distinguishable by the highly seasonal nature of their tanks and poor physical infrastructure relative to lower watershed communities. Such areas are also often buffer zones between as yet uninhabited hinterlands and settled areas where cultivation potentials are further restricted due to wild animal incursions. Consequently, these groups exhibit the greatest dependence on exploitation of the natural resource base. This often includes less seasonal tanks in lower PCs where fisheries are of less significance to local livelihoods. Such low-level ‘poaching’ is generally well tolerated, but potential for conflict exists where development efforts restrict hitherto free access to these resources. These findings were the basis for two phases of action research which involved the stocking of ten tanks belonging to seven communities in North West Province (2000-2001). Phase 1 trials encompassed a range of social and physical and settings from lower to upper watershed. Results indicated that the use of costly hatchery-produced seed was unlikely to be sustainable given (1) a background of highly erratic natural production (2) uncertain returns to individual effort and (3) a low priority accorded to fish production from village tanks given the availability of low-cost commercial production from perennial reservoirs. The second phase was restricted to low-caste communities in upper watershed areas and relied entirely on wild-fish stocks captured from perennial reservoirs lower in the watershed. Also emphasis was on intermittent ‘staggered’ harvesting using hook and line gears rather than the single intensive ‘collective harvests’ adopted in phase 1 trials. High yield potentials were demonstrated in the smallest tanks (<4ha) which were devoid of fish stocks during two pervious drought years. Results also indicate that sustainable adoption will be likely only where there is strong social cohesion and representative village leadership. An adaptive learning process which can demonstrate the net benefits of staggered harvesting in seasonal tanks is described. These stocking strategies combined with tank rehabilitation sympathetic to preservation of upstream hydrological linkages, are highly complementary enhancement steps. Results clearly show that together they have potential to maintain the wider aquatic ecosystem on which the poorest groups depend.

Twenty-eight species of zooplankton were identified from Lake Texoma. Seasonal density of the overall microcrustacean community and seasonal cycles of individual species were compared with northern populations and any available literature from the Southwest. Cycles of occurrence and abundance were similar to those observed in northern populations but tended to occur earlier in the year due to higher temperatures. Spatial distributions within the reservoir were heavily influenced by nutrient and salt input from the Red River, which resulted in dense populations in the Red River Arm. In addition, during the summer, the microcrustacean community was restricted to the epilimnion due to anoxic conditions in the hypolimnion of the reservoir.

Thesis (M.S.)--Miami University, Dept. of Zoology, 2009. / Title from first page of PDF document. Includes bibliographical references (p. 17-21).

Made available in DSpace on 2016-06-02T19:31:34Z (GMT). No. of bitstreams: 1 DissALS.pdf: 2333068 bytes, checksum: cdcfee1bad9d14e51961d064d78ac179 (MD5) Previous issue date: 2006-02-24 / Universidade Federal de Sao Carlos / The reservoirs are artificial ecosystems constructed by the man and attend to the multiple uses. The reservoir provokes alterations in the aquatic ecosystem, causing modifications in the chemical and physical composition of the sediment and of the water and consequently in the circulation and the organization of the biological communities. The purpose of this study was to characterize the taxonomic composition and the benthic community density in 3 reservoirs of the Middle Tietê River (Barra Bonita, Bariri and Ibitinga), to analyze the physical and chemical characteristics of the water and of the sediment and to verify the possible relation of these with the structure of the benthic community, considering the populations of the native species and the invading species Melanoides tuberculata and Corbicula fluminea. The samplings were carried out in two climatic periods, the rainy season (November 2002) and the dry season (August 2003), showing three portions in each reservoir (upper, middle and lower) and following a sweeping with 6 sampling points in each transect. In each point, the samples of sediment were collected in duplicate with one drag of the type van Veen. Based on the limnological data the reservoirs of Barra Bonita and Bariri were classified as whereas Ibitinga Reservoir was characterized as mesotrophic for the periods evaluated. In November 2002, 21, 29 and 25 taxa of macroinvertebrates were registered in Barra Bonita, Bariri and Ibitinga reservoirs, respectively, while in August 2003, there were 23, 31 and 27 taxa, respectively, in each reservoir. A greater similarity between the benthic macroinvertebrates was found for the associations sampled in both periods in the same reservoir than between the different reservoirs, evidencing that each environment have a particular composition of taxa, although some taxa are common among them. The invading species M. tuberculata e C. fluminea were current in all the reservoirs, in both periods of sampling, except in the Barra Bonita reservoir. The generalized occupation of M. tuberculata and the high densities of this specie in the studied reservoirs reveal the high invading potential of same and the probable competition with the native species. / As represas são ecossistemas artificiais construídos pelo homem e destinadas a múltiplos usos. A condição de represa provoca alterações no ecossistema aquático, causando modificações na composição química e física do sedimento e da água, e conseqüentemente na circulação e na organização das comunidades biológicas. O objetivo deste trabalho foi caracterizar a composição taxonômica e a densidade da comunidade bentônica em três represas do sistema Tietê (Barra Bonita, Bariri e Ibitinga), analisar as características físicas e químicas da água e do sedimento e, verificar a possível relação dessas com a estrutura da comunidade bentônica, considerando as populações das espécies nativas e as espécies invasoras Melanoides tuberculata e Corbicula fluminea. As coletas foram realizadas em dois períodos climáticos, o chuvoso (novembro de 2002) e o seco (agosto de 2003), amostrando-se três porções em cada represa (superior, mediana e barragem) e seguindo uma varredura com 6 pontos amostrais em cada transecto. Em cada ponto as amostras de sedimento, foram coletadas em réplicas com uma draga do tipo van Veen. Os resultados obtidos para as variáveis limnológicas classificaram as represas de Barra Bonita e Bariri como eutróficas, enquanto a represa de Ibitinga apresentou características mesotróficas, durante os períodos avaliados. Nas represas de Barra Bonita, Bariri e Ibitinga, em novembro de 2002 foram registrados 21, 29 e 25 táxons e em agosto de 2003 ocorreram 23, 31 e 27 táxons, respectivamente. Foi registrada uma maior similaridade entre as associações amostradas nos dois períodos de cada represa do que entre as diferentes represas, sendo que cada ambiente possui uma comunidade de macro-invertebrados com composição taxonômica particular, embora compartilhem parte dos táxons. As espécies invasoras M. tuberculata e C. fluminea foram encontradas em todas as represas, em ambos os períodos de coleta, exceto na represa de Barra Bonita. A ocupação generalizada de M. tuberculata e C. fluminea e as elevadas densidades destas espécies nas represas estudadas revelam o alto potencial invasor das mesmas e a provável competição com as espécies nativas.

Applicaciò d'un model de hydrodinàmica i de qualitat de l'aigua als embassaments de Sau i Boadella / The aim of this work is to have an idea about the behaviour of Sau and Boedella reservoirs in term of hydrodynamic and water quality, the models applied for are Dynamic simulation model DYRESM and water quality model CAEDYM. / En la tesi s'ha aplicat el model de qualitat de l'aigua DYREM-CAEDYM als embassaments de Sau i Boadella. Els models de qualitat de l'aigua són capaços de predir l'evolució física, química i biològica dels embassaments. Un cop inicialitzats i calibrats ens poden donar informació de com evolucionarà, per exemple, el fòsfor dissolt i les poblacions d'algues. Per funcionar, aquests models necessiten nodrir-se diàriament amb dades meteorològiques com ara la radiació solar, la velocitat del vent o les precipitacions, les quals es poden obtenir d'estacions meteorològiques properes als embassaments. També calen dades biològiques que han estat facilitades per diferents persones i organismes com el Departament d'Ecologia de la Universitat de Barcelona i l'Agència Catalana de l'Aigua. Aquests models no són fàcils de manejar i el primer que s'ha de fer és estudiar-ne la seva aplicabilitat. Concretament, cal saber si poden ser d'una dimensió o en cal un nombre superior. Això es fa comprovant l'evolució de diferents nombres adimensionals, com per exemple els de Wedderburn i Burger. Un cop calibrat, el model DYRESM-CAEDYM prediu -molt bé- l'evolució de la temperatura i -bastant bé- la de l'oxigen dissolt, sobretot a l'embassament de Sau,indicant la presència de zones anòxiques al fons. La tendència en l'evolució del fòsfor dissolt també s'hi veu ben reflectida. En canvi, les simulacions de la clorofila-a, indicativa de les algues, no són tan acurades ja que depenen de molt factors, alguns dels quals no queden prou reflectits en el model. L'objectiu final de la tesi és poder millorar la gestió dels embasaments indicant, per exemple, quina és la fondària òptima d'extracció de l'aigua.

CAPES / A água é fundamental para o equilíbrio ecológico e manutenção da vida, entretanto perturbações de diferentes magnitudes têm alterado seriamente sua qualidade. Nesse sentido, diversas metodologias de análise buscam mensurar o seu grau de contaminação, utilizando avaliação de parâmetros físicos, químicos e biológicos. Reservatórios podem ser classificados como ecossistemas semi-lóticos originados a partir do represamento de rios e a distribuição de organismos nesse corpo hídrico é influenciada pelas características físicas, químicas e interações biológicas e ecológicas. O reservatório do rio Verde localiza-se na divisa dos municípios de Campo Largo e Araucária, Estado do Paraná. O presente estudo teve por finalidade a caracterização física e química de água e sedimentos, assim como avaliação da macrofauna nectônica e bentônica em quatro pontos do reservatório ao longo das quatro estações climáticas entre os anos de 2013 e 2014. Quanto aos parâmetros físicos e químicos, todos à exceção da matéria orgânica encontram-se dentro dos valores preconizados por legislações pertinentes. A macrofauna do reservatório mostrou-se rica e diversificada. Ao total foram coligidos 1880organismos, sendo 938 exclusivamente no sedimento. Ao longo do período amostral foi registrada a presença de táxons bioindicadores, assim como organismos de importância médica e ecológica. De acordo com o teste de regressão linear múltipla, os fatores significativos para a distribuição da comunidade bentônica foram pH, temperatura da água, oxigênio dissolvido, saturação de oxigênio dissolvido, condutividade, material em suspensão (total, orgânico e inorgânico), turbidez, clorofila-a, nitrito, nitrato, matéria orgânica, umidade, fósforo e nitrogênio totais e as frações granulométricas areia média, areia fina e silte/argila. Já para a composição de guildas tróficas, foram registrados cinco grupos: coletores, predadores, raspadores, filtradores e fragmentadores. A partir do teste de regressão linear não-paramétrica, foram consideradas significativas as variáveis turbidez, profundidade e as frações granulométricas. O resultado dos índices de qualidade BMWP' e Diversidade de Shannon-Wiener sugere poluição moderada, resultado que complementa o obtido exclusivamente pelas análises físicas e químicas, corroborando a importância da inclusão da avaliação das comunidades aquáticas e bentônicas em programas de monitoramento ambiental. / Water is essential to the ecological balance and maintenance of life, however disturbances of different magnitudes have seriously affects their quality. In this sense, various analysis methodologies seek to measure the rate of contamination using evaluation of physical, chemical and biological parameters. Reservoirs can be classified as semi-lotic ecosystems originated from the damming of rivers and the distribution of organisms in this water body is influenced by physical, chemical and biological/ecological interactions. The Verde river reservoir is located on the borderland of the cities of Campo Largo and Araucaria, Parana State. The present study aimed the physical and chemical characterization of water and sediment, as well the evaluation of aquatic and benthic macroinvertebrates in four sample points along four seasons in the reservoir between the years 2013 and 2014. Relative to the physical and chemical parameters, all except organic matter are within the recommended values for relevant legislation. The macrofauna of the reservoir proved to be rich and diverse. A total of 1880 organisms were collected, with only 938 in the sediment. Over the sample period was recorded the presence of bioindicators taxa as well organisms of medical and ecological importance. According to the multiple linear regression model, the significant factors for the distribution of the benthic community were pH, water temperature, dissolved oxygen, dissolved oxygen saturation, conductivity, suspended matter (total, organic and inorganic), turbidity, chlorophyll- a, nitrite, nitrate, organic matter, humidity, phosphorus and total nitrogen and grain size medium sand fractions, fine sand and silt/clay. For the composition of trophic guilds, were registered five groups: collectors, predators, scrapers, slicers, filterers and shredders. From the non-parametric linear regression test, were considered significant the variables turbidity, depth and granulometric fractions. The result of the quality index BMWP ' and Shannon -Wiener Diversity suggests moderate pollution, a result that complements that obtained exclusively by physical and chemical analysis, corroborating the importance of including the assessment of aquatic and benthic communities in environmental monitoring programs.

An 18-month study (July 2009 – December 2010) was conducted to determine the influence of four dams located in series along the Perak River, in Malaysia: Temengor, Bersia, Kenering and Chenderoh dams. The framework for investigation centered around the Serial Discontinuity Concept (SDC) and the Cascading Reservoir Continuum Concept (CRCC). In addition to reservoir, tailwater and riverine reach characteristics, the interacting influences of tributary streams and watersheds were addressed. Variables included in-situ environmental physical parameters, nutrients, seston concentration and transport, and fish assemblage characteristics. In-situ variables, water and seston samples, were recorded/collected monthly from all four reservoirs, their associated riverine sections, and their primary tributaries. Fish samples were collected by using experimental gill nets in reservoirs. Fish were enumerated taxonomically and total length and weight were measured for the bony-lipped barb, Osteochilus hasselti (Valenciennes, 1842). Hypotheses were tested using analyses of variance with permutations. Relationships were determined using correlation, and multivariate and regression analyses. The integrated influences of discontinuity and cascading on nutrient and seston transport dynamics and fish assemblages (except for relative condition and biomass of O. hasselti) were operative in dynamic juxtaposition along the river’s continuum, and depended on distance between dams and presence and size of tributary streams. However, principal tributaries along the four serial dams in the Perak River appeared to have little spatial influence on their respective system’s nutrient and seston dynamics due to dilution effects of mainstem discharges. Among all tributaries, only the Rui River depicted reversal of the serial discontinuity trend in its system. Even so, its influence on its system was limited. Effects of ecosystem fragmentation along the river’s continuum on in-situ, nutrients and seston transport dynamics, and fish assemblages existed, but not necessarily in line with the SDC nor in line with the CRCC. The dynamics of in-situ, nutrient, seston and fish assemblage parameters were more associated with land use, reservoir surface area and dam discharge. Results from this study generated a hypothesis that submerged woody vegetation in the reservoirs may augment and compensate lost nutrients, thereby minimizing functional impacts of serially-arranged dams.

Data were collected from natural and introduced fishes present in Ferndale Lake, a small (120 ha) sport fishing reservoir in Camp County, east Texas. Levels of pH measured in the lake during the study period ranged from 3.5 to 5.3. Monthly field surveys and experimental manipulations were designed to evaluate quantitatively the signs of stress at various biological levels. Lethal limits to low pH were quantified for largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) to be pH 3.8 and 4.0,respectively. Mean blood pH (+ 1 SD) of 59 bluegill was 7.41 (j 0.16), with no significant difference (P-0.05) among groups from Ferndale Lake and Moss Lake (Cooke Co., Texas) under experimental conditions, even when severe stress was externally apparent. In a dual-trough horizontal pH gradient, bluegill behavioral avoidance was observed at pH levels below 7.0. Individual testing of 40 bluegill in pH gradient of 5.2 to 7.6 resulted in median occupation of pH 7.1,with an interquartile range of pH 6.9 to 7.3. Decreased community structure and population "well being" compared to early studies cannot be attributed entirely to recent acidic condition. Separating potential stress due to lake conditions from that due to heavy biotic predation by sport fishing in a small reservoir is difficult.

Made available in DSpace on 2016-06-02T19:31:53Z (GMT). No. of bitstreams: 1 3488.pdf: 3068626 bytes, checksum: 4c31a6cd33b71b943b63182f4a5a1026 (MD5) Previous issue date: 2011-02-11 / Universidade Federal de Sao Carlos / The UHE Furnas Reservir is located in the state of Minas Gerais and it was built for hydroelectricity generation in 1963, although it is present used for multiple purposes. The zooplankton communities of freshwaters are composed by a variety of species belonging to several taxonomic (Cladocera, Copepoda, Rotifera, Protozoa, larvas de Insecta, Ostracoda, Turbellaria), and are all ecologically important. Many species can be indicators being highly sensitive of environmental conditions The aim of the present work was to analyse the spatial and temporal changes in the species composition, diversity and biomass of zooplankton community as well as their interactions with other environmental variables at the UHE Furnas Reservoir. Samplings were carried out each three months in 36 points in the reservoir, including the two major compartments: Sapucai and Grande dammed portions. Measurements of the main physical and chemical variables were carried out in situ and in the laboratory measurements of nutrients, suspended matter and chlorophyll a concentrations were performed. Zooplankton community was sampled by vertical net hauls with plankton net of 68 &#956;m mesh size. Samples were analyzed regarding the species composition, numerical densities and community biomass. The results obtained indicated the water of the UHE Furnas Reservoir has oligotrophic conditions except in a locality upstream, in River Marimbondo compartment and others located distantly from the dam. The reservoir is thermally and chemically stratified regarding temperature and dissolved oxygen. There are also spatial changes and the reservoir can be divided in three major compartments: Sapucaí River compartment; central portion close to the dam and the northern River Grande compartment. Temporal fluctuations occurred for most variables, with strong differences among the dry and rainy periods. The species richness was high and some species were spatially segregated. Copepoda was the most abundant zooplankton group, both in numbers and biomass. The highest densities and biomass were found in the central portion of the reservoir during the rainy period. In general, the highest concentrations of chlorophyll, zooplankton density and biomass occurred in the Sapucaí River compartment, indicating its higher trophic condition as compared to the more oligotrophic River Grande compartment. Zooplankton biomass as a whole is low compared to other reservoirs, as expected for an oligotrophic system. / O reservatório da UHE de Furnas está situado em Minas Gerais e foi construído em 1963 para produção de energia elétrica, porém atualmente é utilizado para múltiplos fins. A comunidade zooplanctônica em águas doces é composta por um conjunto de organismos pertencentes a diversos grupos taxonômicos (Cladocera, Copepoda, Rotifera, Protozoa, larvas de Insecta, Ostracoda, Turbellaria), possui grande importância ecológica nos ambientes aquáticos e muitas espécies são utilizadas como bioindicadoras já que possuem grande sensibilidade ambiental. O objetivo desse trabalho foi analisar as variações espaciais e temporais da composição, diversidade e biomassa da comunidade zooplanctônica e suas relações com as variáveis ambientais do reservatório da UHE de Furnas. As amostragens foram trimestrais em 36 pontos do reservatório, incluindo os dois grandes compartimentos: rio Sapucaí e rio Grande. Medidas das principais variáveis físicas e químicas foram realizadas in situ e em laboratório foram determinadas as concentrações de nutrientes, material em suspensão e clorofila a. Amostras de zooplâncton foram coletadas por arrastos verticais através de uma rede de plâncton com malha de 68 &#956;m. Foram analisadas a composição de espécies, densidade numérica e biomassa da comunidade. Os resultados indicam que o reservatório da UHE de Furnas possui condições oligotróficas com exceção da localidade situada na região represada do rio Marimbondo e localizadas às montantes da barragem. O reservatório é termicamente e quimicamente estratificado demonstrado pelos perfis de temperatura e oxigênio dissolvido. Existem variações espaciais podendo ser dividido em três porções: montante do compartimento rio Sapucaí, parte central próxima à barragem e montante do compartimento rio Grande. Variações temporais também foram verificadas para a maioria das variáveis analisadas, relacionadas ao verão chuvoso e inverno seco. A riqueza de espécies foi grande e algumas espécies apresentaram padrão espacial de ocorrência. O grupo Copepoda foi mais abundante em relação aos demais grupos tanto em densidade quanto em biomassa. Maiores densidades numéricas e biomassas foram registradas no período chuvoso e na parte central do reservatório. Maiores concentrações de clorofila a, densidade e biomassa zooplanctônicas foram registradas nos pontos localizados no compartimento rio Sapucaí quando comparado ao compartimento rio Grande. A biomassa zooplanctônica do reservatório da UHE de Furnas é baixa quando comparada a outros reservatórios como esperado para um sistema oligotrófico.

CAPES; CNPq; Fundação Araucária / O conhecimento das alterações ecológicas em um reservatório é de grande relevância para estudos de impacto ambiental e de avaliação de qualidade da água, sobretudo, o conhecimento da estrutura da comunidade fitoplanctônica, que têm uma importância fundamental dentro dos ecossistemas aquáticos, pois respondem de forma rápida às mudanças físicas e químicas da água, e contribuem de forma acentuada para a produção de matéria orgânica. O objetivo deste trabalho foi analisar a composição e abundância da comunidade fitoplanctônica sob influência das variáveis abióticas dentro de um eixo longitudinal em quatro reservatórios em cascata destancando a importância das populações de cianobactérias. Localizados no estado do Paraná, os reservatórios das Hidreléticas do rio Iguaçu; Foz do Areia, Salto Segredo, Salto Santiago e Salto Caxias foram escolhidos como área de estudo porque recebem alta carga de nutrientes de origem antrópica, com elevadas concentrações de fósforo e nitrogênio, e como consequência, a formação de frequentes florações. Para realização do estudo foram coletadas amostras para análise das variáveis abióticas e bióticas em doze pontos no reservatório de Foz do Areia, e em nove pontos nos demais reservatórios (Segredo, Santiago e Caxias), distribuídos da seguinte forma: três na região fluvial, três na intermediária e três na região lacustre, nos meses de novembro de 2012, fevereiro de 2013 e outubro de 2013. As amostras qualitativas de fitoplâncton foram coletadas através de uma rede de plâncton, e as quantitativas foram coletadas diretamente do ambiente. Todas as amostras foram fixadas imediatamente. A identificação das espécies foi realizada com o auxílio de um microscópio comum, enquanto a contagem dos indivíduos foi realizada utilizando câmara de sedimentação tubular em microscópio invertido. Foram feitas análises dos parâmetros físicos e químicos da água. Durante o período estudado foram registrados 232 táxons no total que pertenceram a 10 classes. As cianobactérias foram dominantes nos quatro reservatórios estudados, sendo responsável pelas florações ocorridas, principalmente sob influência das densidades de Microcystis aeruginosa e Sphaerocavum brasiliense nos reservatórios de Foz do Areia e Salto Segredo, nos meses de novembro de 2012 e fevereiro de 2013. A dominância de cianobactérias associadas à elevada temperatura e concentração de nutrientes nos reservatórios, mostram que o rio Iguaçu está passando por um intenso processo de degradação ambiental, que pode ameçar a integridade das comunidades biológicas e causar sérios danos à saúde do ecossistema como um todo. / Knowledge of ecological changes in a reservoir is of great relevance to the study environmental impact and of the water quality, especially the knowledge of phytoplankton community estructure, that has a role importante in aquatic ecosystems, which respond quickly to physical and chemical changes of the water, and markedly contribute to the production of organic matter. The objective of this work was to analyze the composition and abundance of phytoplankton under the influence of abiotic variables along a longitudinal axis in four reservoirs in a cascade system, emphasizing the importance of cyanobacteria populations. Located in the state of Parana, the reservoirs of hydroeletric stations of the Iguaçu River, namely, Foz do Areia, Salto Segredo, Salto Caxias and Salto Santiago, were chosen as the study area because they receive high nutrient load of anthropogenic origin, which contributes to increased concentrations of nitrogen and phosphorus, and consequently the formation of frequent blooms. To conduct this study were collected samples for analysis of abiotic and biotic variables in twelve points in the reservoir of Foz do Areia and nine points in the other reservoirs (Segredo, Santiago e Caxias), distributed as follows: three in river region, three in the intermediate region and three in the lake region, in November 2012, February 2013 and October 2013. Qualitative samples of phytoplankton were collected through a plankton net, and quantitative were collected directly from the environment. All samples were fixed immediately. The identification of the species was made with the aid of an common microscope, while the phytoplankton counting was made tubular sedimentation chamber using an inverted microscope. Analysis of physical and chemical parameters of water were made. During the study period, a total of 232 taxa were recorded that belonged to 10 classes. The cyanobacteria were dominant in the four reservoirs studied, being responsible for blooms occurred mainly under the influence of Microcystis aeruginosa and Sphaerocavum brasiliense densities in the reservoirs in Foz do Areia and Salto Segredo in November 2012 and February 2013. The dominance of cyanobacteria associated with high temperature and nutrient concentration in the reservoirs, show that the Iguazu River is undergoing an intense process of environmental degradation, which can threaten the integrity of biological communities and cause serious damage to the health of the ecosystem as a whole.