The species composition and abundance of the zooplankton community of seven reservoirs of the Paranapanema River, located between 22 degrees 37'-23 degrees 11'S and 48 degrees 55'-50 degrees 32'W, were analysed over four periods, in the year of 1979. The zooplankton community was composed of 76 species of Rotifera, 26 species of Cladocera and 7 species of Copepoda. For a large part of the period under study the Rotifera were dominant, followed by Copepoda. The Piraju and Salto Grande reservoirs, which occupy intermediate positions in the cascade of reservoirs, were richest in species, most of them belonging to Rotifera and Cladocera. In the reservoirs Rio Pari and Rio Novo, lateral to the cascade of reservoirs, a lower species richness was observed, although higher densities of organisms were found than in the other reservoirs located in the main river body. Different rotifer species occurred in succession, being abundant in different periods, with no defined pattern. Among the copepods, Thermocyclops decipiens predominated in the majority of the reservoirs. Ceriodaphnia cornuta was the most abundant cladoceran in the intermediate reservoirs of the cascade, and Daphnia gessneri, Bosminopsis deitersi and Moina minuta, in the reservoirs lateral to the cascade. The most frequent zooplankton species were Notodiaptomus conifer, Thermocyclops decipiens, Ceriodaphnia cornuta cornuta and C. cornuta rigaudi, Daphnia gessneri, Bosmina hagmanni, Keratella cochlearis and Polyarthra vulgaris. Some relationships were found between the trophic state of the reservoirs and the zooplankton community.

The chapter presents state-of-the-art of reservoir limnology and water quality modelling and their use in reservoir water quality management. Reservoirs are classified into dam reservoirs and impoundments. The features of dam reservoirs and lakes are confronted, both qualitative (absolute) and quantitative (relative) differences being specified. Different consequences of reservoir construction for the river are outlined. Methodological problems concerning sampling and mathematical modelling are dealt with. Theoretical aspects of reservoir limnology cover the position of reservoirs in the river continuum concept, retention time as a key factor of reservoir limnology and reservoir aging (short term trophic upsurge) and long term reservoir ecosystem evolution. Pulse effects are treated as a theoretical problem with considerable consequences for reservoir management. Specific attention is devoted to multiple reservoir systems. Reservoir water quality management approaches and options as well as their use for specific reservoir uses are analyzed. The perspective for future reservoir investigations is treated.

An unusual bloom of Ceratium furcoides is reported for a station of the Taquacetuba compartment of the Billings Reservoir. The appearance of this bloom is attributed to the mixing and turbulence of the water column that removed Ceratium cysts from the surface of the sediment and promoted conditions for the growth of this species in the region of mixing. Cold fronts approaching the Billings Reservoir are probably the cause of the mixing and bloom. Also turbulence induced by wind increased phosphorus concentration in the water column. Ceratium furcoides was the dominant species at station 1 where the nutrient concentrations of nitrogen and phosphorus were high. Ceratium spp. blooms may be a problem for water treatment and massive mortality can affect the dissolved oxygen of the water producing fish kill.Keywords: Ceratium furcoides, blooms, turbulence, cysts, cold fronts. Ocorrência de floração de Ceratium furcoides ( Levander) Langhans 1925, na represa Billings, Estado de São Paulo, Brasil ResumoNeste trabalho, apresenta-se e discute-se a formação de florescimento de Ceratium furcoides no compartimento Taquacetuba da Represa Billings. Este florescimento é provavelmente resultado de intensa mistura vertical de coluna de água na região de transição entre este compartimento e o corpo central da represa. Esta mistura vertical é resultado do efeito de frentes frias sobre o sistema, promovendo interfaces que favorecem o aumento acentuado de fósforo na região do florescimento e o rápido crescimento de Ceratium furcoides. A turbulência gerada pode ter removido cistos da superfície do sedimento, promovendo o rápido crescimento desta espécie. O florescimento de espécies de Ceratium spp. pode ser problemático para o tratamento de água, pois pode causar depleção de oxigênio dissolvido após a decomposição, comprometendo a qualidade da água e aumentando os custos do tratamento.

This paper describes and discusses the impacts of the passage of cold fronts on the vertical structure of the Carlos Botelho (Lobo-Broa) Reservoir as demonstrated by changes in physical, chemical, and biological variables. The data were obtained with a continuous system measuring 9 variables in vertical profiles in the deepest point of the reservoir (12 m) coupled with climatological information and satellite images, during a 32-day period in July and August, 2003. During periods of incidence of cold fronts the reservoir presented vertical mixing. After the dissipation of the cold fronts a period of stability followed with thermal, chemical, and biological (chlorophyll-a) stratification. Climatological data obtained during the cold front passage showed lower air temperature, higher wind speed and lower solar radiation. The response of this reservoir can exemplify a generalized process in all shallow reservoirs in the Southeast Brazil and could have several implications for management, particularly in relation to the phytoplankton population dynamics and development of cyanobacterial blooms. Using this as a basis, a predictive model will be developed with the aim of advancing management strategies specially for the drinking water reservoirs of the Metropolitan Region of São Paulo.

In this paper the authors report and discuss limnological information for reservoirs in Brasil including physical, chemical and biological data in order to provide an insight into some basic mechanisms and interrelationships of forcing functions, biological and biogeochemical factors useful for management.The introduction of ecotechnological measures to control, reduce eutrophication, suspended mater input and to recover water quality, is very urgent.Basic theoretical problems of reservoirs structure and function are discussed as well as the introduction of new techniques such as satellite image to improve management.

As in many other continents, neotropical ecosystems are impacted by the construction of reservoirs. These artificial ecosystems change considerably the natural terrestrial and aquatic ecosystems and their biodiversity. The multiple uses of reservoirs promote benefits for the human beings in terms of economic development, income, jobs and employment. Services of reservoirs are important assets for the regional ecosystem. Evaluation of ecosystem services produced by artificial reservoirs, are new challenges to the understanding of the cost/benefit relationships of reservoir construction in the neotropics. Regulating and other services promoted by reservoirs lead to new trends for "green technology" and the implementation of ecohydrological and ecotechnological developments. This approach can be utilized with better success as a substitute for the usual impact/benefit evaluation of the reservoirs. Better and diversified services can be achieved with "green technology" applied to the construction.Keywords: neotropics, reservoir, services, evaluation, cost benefit analysis. Reservatórios e o bem estar humano: novos desafios para avaliar os impactos e os benefícios nas regiões neotropicais ResumoRegiões neotropicais são impactadas pela construção de reservatórios em várias bacias hidrográficas. Estes sistemas artificiais produzem consideráveis alterações nos sistemas naturais terrestres e aquáticos e na biodiversidade. Os múltiplos usos dos reservatórios proporcionam muitos benefícios para as comunidades humanas, como desenvolvimento econômico, emprego, e renda. Os serviços proporcionados pelos reservatórios são inúmeros e diversificados e são importantes bases sociais e econômicas para o ecossistema regional. A avaliação destes serviços produzidos pelos reservatórios artificiais apresenta novos desafios para a compreensão da complexa relação custo/beneficio da construção de reservatórios nos neotrópicos. Serviços de regulação, e outros serviços produzidos pelos reservatórios, podem ser uma rota fundamental para o desenvolvimento de tecnologias sustentáveis e a implementação de conceitos de ecohidrologia e ecotecnologias. Esta abordagem pode ser utilizada com sucesso na substituição da abordagem usual de balanços benefícios/impactos da construção de reservatórios e proporciona novas oportunidades para avaliação adequada dos reservatórios construídos e das novas construções.Palavras-chave: neotrópicos, reservatório, impactos, serviços, avaliação custo/beneficio.

The dominance patterns of the main zooplankton groups depend on whether they are analysed by numerical density or dry weight. This fact is discussed in relation to the trophic state of the system.Biomass of planktonic crustaceans from Broa reservoir was analysed by dry weight. For Argyrodiaptomusfurcatus organic carbon was also determined. Values of 4.42 pg C ind. -' and 6.83 pg C ind. -r were obtained for males and females, respectively.Seasonal fluctuation of the species showed two peaks of abundance: the rainy season (summer), and the windy period (winter), these factors being thus the principal controlling forces for the growth of the populations.

The objective of this study was to determine the effects of land-use patterns on both diatom community composition and water quality in tropical streams during the dry season. Benthic diatom collections and water quality sampling were done 4 times at 10 sites. A suite of environmental variables that varied with human land-use pattern was assessed to find the combination of variables that best explained patterns of diatom community composition. Canonical Correspondence Analysis (CCA) was used to determine environmental gradients along which species were distributed. A clear relationship between both benthic diatom communities and water quality and land-use pattern was observed with species richness, diversity and evenness, decreasing significantly from the agricultural and forest area to the urban area. Upstream, forested, agricultural sites, with good water quality (BOD 5 = 0.9 to 2.6 mg•ℓ