Large reservoirs are an increasingly common feature across tropical landscapes because of their importance for water supply, flood control and hydropower, but their ecological conditions are infrequently evaluated. Our objective was to assess the range of disturbances for two large tropical reservoirs and their influences on benthic macroinvertebrates. We tested three hypotheses: i) a wide variation in the level of environmental disturbance can be observed among sites in the reservoirs; ii) the two reservoirs would exhibit a different degree of disturbance level; and iii) the magnitude of disturbance would influence the structure and composition of benthic assemblages. For each reservoir, we assessed land use (macroscale), physical habitat structure (mesoscale), and water quality (microscale). We sampled 40 sites in the littoral zones of both Três Marias and São Simão Reservoirs (Minas Gerais, Brazil). At the macroscale, we measured cover percentages of land use categories in buffer areas at each site, where each buffer was a circular arc of 250 m. At the mesoscale, we assessed the presence of human disturbances in the riparian and drawdown zones at the local (site) scale. At the microscale, we assessed water quality at each macroinvertebrate sampling station using the Micro Disturbance Index (MDI). To evaluate anthropogenic disturbance of each site, we calculated an integrated disturbance index (IDI) from a buffer disturbance index (BDI) and a local disturbance index (LDI). For each site, we calculated richness and abundance of benthic macroinvertebrates, Chironomidae genera richness, abundance and percent Chironomidae individuals, abundance and percent EPT individuals, richness and percent EPT taxa, abundance and percent resistant individuals, and abundance and percent non-native individuals. We also evaluated the influence of disturbance on benthic macroinvertebrate assemblages at the entire-reservoir scale. The BDI, LDI and IDI had significantly greater average scores at São Simão than at Três Marias Reservoir. The significantly greater differences in IDI scores for São Simão Reservoir were reflected in 10 of the 13 Ekman-Birge dredge biotic metrics and in 5 of 13 of the kick-net biotic metrics. We also observed clear ranges of disturbances within both reservoirs at macro (BDI) and mesoscales (LDI) and in water quality, but an insignificant range in MDI results. However, we found no significant relationship between the benthic macroinvertebrate metrics and the BDI, LDI, and IDI among sites within a single reservoir. Hence, we believe that benthic macroinvertebrate distributions in those reservoirs were influenced by other factors or that reservoir macroinvertebrates (dominated by chironomids) were poor indicators of disturbance at the site scale.

Reservoirs are artificial ecosystems with multiple functions having direct and indirect benefits to humans; however, they also cause ecological changes and influence the composition and structure of aquatic biota. Our objectives were to: (1) assess the environmental condition of Nova Ponte Reservoir, Minas Gerais state, southeastern Brazil; and (2) determine how the aquatic biota respond to disturbances. A total of 40 sites in the littoral zone of the reservoir were sampled to characterize physical and chemical habitat, land use, and benthic macroinvertebrate and fish assemblages. The predominant type of land cover near the reservoir was natural vegetation. A total of 29 fish species and 39 macroinvertebrate taxa were collected, including eight alien species. Most sites had intermediate levels of human disturbance, however, high levels of degradation were associated with high proportions of alien species. Disturbances at multiple scales may alter natural patterns and processes, leading to environmental changes and damaging biological communities. Our results reinforce the importance of assessing reservoir ecological conditions at several scales. The study of land use, littoral zone physical habitat characteristics, water quality, and assemblage structure set the ground for proposing actions to rehabilitate and conserve aquatic ecosystems. Keywords: reservoirs, water quality, bioindicators, physical habitat, environmental quality.MARTINS, I., SANCHES, B., KAUFMANN, P.R., HUGHES, R.M., SANTOS, G.B., MOLOZZI, J., CALLISTO, M. Avaliação Ecológica de um reservatório no sudeste do Brasil.http://dx.doi.org/10.1590/1676-06032015006114Resumo: Reservató rios sã o ecossistemas artificiais com mú ltiplas funçõ es e que oferecem benefícios diretos e indiretos ao homem; no entanto, também causam mudanças ecoló gicas e influenciam a composiçã o e estrutura da biota aquá tica. Os objetivos deste estudo foram: (1) avaliar a condição ambiental do reservató rio de Nova Ponte, Estado de Minas Gerais, sudeste do Brasil; e (2) verificar se a biota aquá tica responde aos distú rbios. No total, 40 sítios amostrais na regiã o litorâ nea do reservató rio foram amostrados para caracterizar os habitats físicos e químicos, cobertura e uso do solo, assembleias de macroinvertebrados e peixes. Vegetaçã o natural de cerrado foi o tipo predominante de cobertura do solo no entorno do reservató rio. 29 espécies de peixes e 39 taxa de macroinvertebrados bentô nicos foram coletadas, incluindo oito espécies exó ticas. A maioria dos sítios amostrais possui níveis intermediá rios de distú rbio antró pico, porém o aumento de alteraçõ es antró picas foi associado ao aumento do nú mero e abundâ ncia de espécies exó ticas. Distú rbios em mú ltiplas escalas podem alterar os padrõ es e processos naturais, levando a mudanças ambientais e nas comunidades bioló gicas. Nossos resultados reforçam a importâ ncia de avaliar as condiçõ es ecoló gicas do reservató rio em vá rias escalas. O estudo do uso e cobertura do solo, características de habitats físic...

This book is dedicated to the memory of our friend Volney Vono. We miss him, his funny stories, and his ecological knowledges.

Because of their importance to human well-being and ecosystem services, it is important to have cost-effective methods for assessing reservoir ecological condition or health. To do so, we constructed a preliminary reservoir fish assemblage index (RFAI) to assess the effect of predominantly agricultural land use on two oligotrophic neotropical reservoirs that differed in disturbance level. We first determined the disturbance levels around each reservoir through use of an integrated disturbance index (IDI). The IDI was calculated from the combination of land use metrics at local (Local Disturbance Index -LDI) and buffer scales (Buffer Disturbance Index -BDI).Afterwards, we employed the IDI to assess the response of candidate metrics to environmental disturbance in the RFAI construction. The final RFAI included three metrics selected by range, responsiveness, and redundancy tests. Metrics were scored continuously, and the final RFAI was divided in four quality classes: very poor, poor, acceptable and good. The results showed a clear disturbance gradient in both reservoirs with the IDI values varying between 0.07 and 1.33. However, the IDI values were greater around Volta Grande reservoir because of the predominance of agriculture land use (at local and buffer scales). The RFAI scores in Nova Ponte reservoir were significantly higher than in Volta Grande. All the sites scored as very poor or poor were in Volta Grande and all the sites scored as good were in Nova Ponte.In addition, RFAI scores in the reservoir river arms did not differ from those in the reservoir main body, indicating that it was applicable to both habitat types. Finally, our RFAI scores indicated no significant seasonal difference in the two reservoirs; however, the rainy season produced a greater range and more low scores, particularly in Volta Grande. We related this result to the harmful effect of agriculture and the surface runoff of fertilizers, herbicides, and pesticides. Thus, the RFAI was effective in detecting agricultural impacts at the site scale, even in oligotrophic reservoirs. K E Y W O R D Sagriculture, oligotrophic, RFAI, Upper Paraná River Basin