Damming disrupts lotic continuity, creating a lentic water body upstream of the dam and a lotic stretch downstream that is highly vulnerable to temporal fluctuations in flow and physiochemical quality depending on the operational regime of the dam. Thus, an essential part of any dam operation programme must take into account a typologically suitable environmental flow regime, in order to maintain downstream structure and function. We assessed the seasonal impact of daily flow peaking regimes on the taxonomic composition, metrics and traits of the macroinvertebrate community in the lotic section situated downstream of the Itutinga reservoir on the Rio Grande in the state of Minas Gerais in southeast Brazil. The flow manipulation experiments were carried out in both wet (January) and dry periods (July) of 2010. The samplings were carried out in two hydraulic situations (fixed flow and daily flow peaking). Benthic macroinvertebrates and sediment were collected in three habitat types (backwater, fluvial beach and running water). Water variables were measured only in the fluvial beach habitat. Both water column and sediment variables downstream were heavily influenced by the retention capacity of the reservoir rather than the daily flow peak value. The trait approach was more sensitive than abundance and metrics and could detect the effects of daily flow peaking. The benthic macroinvertebrate communities sampled downstream of the Itutinga reservoir were more influenced by the sediment composition at each of the three studied habitats, than by the tested daily flow peaking. However, given the short timescale of this study, it may be difficult to the influence of these two interrelated factors. Copyright © 2013 John Wiley & Sons, Ltd.

From December 2003 to September 2004, benthic macroinvertebrates (BM), fishes, water and sediment were collected quarterly at six stations in two streams of the upper São Francisco River basin, south-eastern Brazil. We evaluated the ecological conditions, habitat diversity, water quality, composition and structure of BM communities, as well as the food habits of the local fish fauna. By applying a protocol for rapid characterization of ecological conditions and habitat diversity, three of the sampled localities were classified as "pristine" while the others stations were considered "altered". A well oxygenated water with near neutral pH and low electric conductivity (< 0.01 mS/cm) and nutrient concentrations (< 0.08 mg/l total P and < 0.90 mg/l total N) was found for both streams. Sediment analysis revealed the dominance of medium, fine and very fine sand fractions in all sampled areas. The organic matter content in the sediment was higher in the lotic and well preserved area. We found 45 BM taxa, and Chironomidae (68%), Oligochaeta (10%) and Elmidae (8.5%) showed the highest abundances. From the stomach contents analysis of 13 fish species, 26 BM taxa were found, including four that were not collected in the sediment samples, being Chironomidae the dominant group (> 60%). Our results show that human activities such as forest clearing, agriculture and cattle rising have altered the habitat diversity in freshwater ecosystems in a process that affects the aquatic biota and thus the food availability to the fish fauna. The results also highlight the importance of the fish stomach contents analysis as a complementary tool in BM inventories.

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Dams are a major threat to aquatic biological diversity. By altering the natural flow of rivers, dams modify fluvial habitats, making them unsuitable for the growth and reproduction of many aquatic species. The aim of this study was to evaluate the effects of a reduced flow reach (RFR) on benthic macroinvertebrate communities. Benthic macroinvertebrates were collected at six sites downstream of the Amador Aguiar Power Plant I before (lotic phase) and after (semi-lentic phase) Araguari River mean flow was reduced from 346 to 7 m 3 .s -1. Changes in macroinvertebrates richness, diversity and total biomass were not observed. Ablabesmyia, Tanytarsus (Chironomidae, Diptera), Leptoceridae and Polycentropodidae (Trichoptera) densities significantly increased the first year after flow reduction and the construction of spillways (t-test; p < 0.05). An analysis of similarity (ANOSIM) showed statistical differences in taxonomical composition despite considerable overlap in communities between the lotic and semi-lentic phases (R = 0.3; p < 0.01). In both phases, the macroinvertebrates were characterised by the dominance of groups tolerant to human disturbance (e.g., Chironomidae, Ceratopogonidae and Oligochaeta) and by the presence of the alien bivalve species Corbicula fluminea (Veneroidae), suggesting that the river was already degraded before the hydraulic modifications. Since the 1980s, the Araguari River has been continuously subjected to human pressures (e.g., cascade dams, urbanization and replacement of native vegetation by pasture and crops). These activities have led to impoverishment of biological communities and have consequently altered the ecosystem.Keywords: spillways, reduced flow, dams, benthic, anthrophic impacts.Efeitos da redução de vazão e construção de soleiras vertentes sobre a composição e estrutura de comunidades de macroinvertebrados bentônicos em um trecho de rio brasileiro ResumoAs represas constituem uma das principais ameaças à diversidade biológica. Ao alterarem a vazão natural de um rio, modificam os habitats fluviais tornando-os inadequados para o crescimento e reprodução de diversas espécies aquáticas. O objetivo deste estudo foi avaliar os efeitos de um trecho de vazão reduzida sobre as comunidades de macroinvertebrados bentônicos. Os organismos foram coletados em seis estações amostrais à jusante da UHE Amador Aguiar I antes (fase lótica) e após (fase semilêntica) a vazão média do rio Araguari (MG) ter sido reduzida de 346 para 7 m 3 .s -1. Não foram registradas mudanças na riqueza, diversidade e biomassa total dos macroinvertebrados. As densidades (ind.m -2 ) de Ablabesmyia, Tanytarsus (Diptera), Leptoceridae e Polycentropodidae (Trichoptera) aumentaram significativamente no primeiro ano após a redução da vazão e construção das soleiras vertentes (t-test; p < 0,05). Uma análise de similaridade (ANOSIM) apontou diferenças significativas na composição taxonômica, porém houve sobreposição das comunidades entre as fases lótica e semilêntica (R = 0,3; p < 0,01). Em ambas as fases a ma...

Despite the fundamental importance of reservoirs and dams for socioeconomic development, their presence results in large‐scale alterations to the natural flow regime of the rivers and profoundly influences aquatic processes and biodiversity. This study compared macroinvertebrate community composition and structure metrics, as well as biological and ecological traits to evaluate their dependence on inter‐seasonal and intra‐seasonal flows and water quality downstream of the Itutinga reservoir situated on Rio Grande in Brazil. The results demonstrated the utility of benthic macroinvertebrate abundance, density, richness, size, reproduction, locomotion and feeding modes to assess flow regime and water quality variability. Changes in the macroinvertebrate communities were closely associated with seasonal differences in parameters such as temperature, turbidity and nutrients, which were modulated by substrate particle size and heterogeneity. Modification of the flow regime, as a result of river regulation, influences the composition, structure and functioning of river ecosystems and is reflected in changes to the aquatic communities they support. The results of this study highlight the extreme complexity of the links between physicochemical, hydrological and biological processes in lotic systems and the need to better understand these links in order to develop and implement optimal environmental flow regimes in regulated rivers. Copyright © 2015 John Wiley & Sons, Ltd.

Rapid Ecological Assessment protocols are important tools for the training of postgraduate students, as well as the collection of data on poorly-known and protected areas with the potential for the preservation of water supplies for urban areas. The objective of this study was to perform a survey of water quality and diversity of benthic macroinvertebrates in two sub-basins at the Mata do Junco Wildlife Refuge in the Brazilian state of Sergipe. The collection of data in the field, laboratory processing, and the interpretation and discussion of data were conducted in groups by students from two postgraduate programmes in Ecology and Conservation (UFMG and UFS), personnel of the state environment agency (SEMARH), school teachers from the local town of Capela, and members of the reserve's voluntary fire brigade. The results of the assessment were organised, analysed, and presented at the reserve headquarters in the form of posters, for the development of environmental education activities with pupils from local schools, as well as contributing to a SEMARH seminar. Samples were characterised by distinct taxonomic compositions and diversity, as confirmed by MDS and additive partitioning of diversity analyses. The gravel substrate presented the lower mean taxonomic richness in each sampling unit (a 1 = 28%), while the average difference among samples (b 1 diversity) was elevated for both substrates (39% for leaf litter, 41% for gravel), reflecting the pronounced variation among samples, even adjacent ones within the same stream. Diversity between streams was lower in the case of leaf litter in comparison with gravel (b 2 = 21 and 31%, respectively). A total of 57 fish specimens were collected with a predominance of individuals of the orders Characiformes (62%) and Perciformes (21%). This rapid ecological assessment confirmed the importance of the conservation unit and emphasised the need for its continuation, given its importance for the maintenance of water quality and its other ecological services, such as the conservation of the region's aquatic biodiversity and providing the local town of Capela (circa 20,000 inhabitants) with its water supply, the Mata do Junco being its only source.

La operación de numerosas presas se realiza con el propósito de regular el caudal de los ríos a escala temporal diaria y estacional, para poder aportar energía tanto en picos de consumo como en épocas de bajo caudal o de sequías. Dicha regulación cambia las características del agua y de los ecosistemas acuáticos, alterando la dinámica de materia y energía, la disponibilidad de hábitat físico, y en conjunto la integridad de los ecosistemas. Este estudio propuso un régimen ecológico de caudales para mejorar el estado ecológico del Río Grande bajo la central hidroeléctrica de Itutinga (Minas Gerais, Brasil). En el diseño del régimen ecológico de caudales se combinaron las siguientes herramientas: i) Series temporales de caudales medios diarios; ii) análisis de la respuesta biológica de las comunidades de peces y macro-invertebrados acuáticos ante un experimento de manipulación de los picos de caudales, aguas abajo de la misma central; iii) análisis del régimen actual de caudales mediante Indicadores de Alteración Hidrológica (IHA). La representación del régimen ecológico anual, con un rango de variabilidad, fue construido a partir de un modelo autorregresivo cuyas restricciones fueron obtenidas mediante análisis de cinco componentes fundamentales del régimen hidrológico (magnitud, frecuencia, duración, temporalidad y tasas de cambio) del período anterior (1934-1954) y posterior a la construcción de la presa (1990-2011). Además de los IHA, para la magnitud del caudal se consideró la respuesta biológica de las comunidades de peces y macroinvertebrados acuáticos, así como algunos límites de operación de la central indicados por la empresa hidroeléctrica. El método desarrollado aporta una perspectiva novedosa para los caudales ecológicos en América Latina, debido a su enfoque multidisciplinar, ya que integra información hidrológica, biológica, y datos sobre la operación de presas.