RESUMO

Biological diversity can be divided into: alpha (α, local), beta (ß, difference in assemblage composition among locals), and gamma (γ, total diversity). We assessed the partitioning of taxonomic diversity of Ephemeroptera, Plecoptera and Trichoptera (EPT) and of functional feeding groups (FFG) in neotropical savanna (southeastern Brazilian cerrado) streams. To do so, we considered three diversity components: stream site (α), among stream sites (ß1), and among hydrologic units (ß2). We also evaluated the association of EPT genera composition with heterogeneity in land use, instream physical habitat structure, and instream water quality variables. The percentage of EPT taxonomic α diversity (20.7%) was smaller than the ß1 and ß2 diversity percentages (53.1% and 26.2%, respectively). The percentage of EPT FFG collector-gatherer α diversity (26.5%) was smaller than that of ß1 diversity (55.8%) and higher than the ß2 (17.7%) diversity. The collector-gatherer FFG was predominant and had the greatest ß diversity percentage among stream sites (ß1, 55.8%). Our findings support the need for implementing regional scale conservation strategies in the cerrado biome, which has been degraded by anthropogenic activities.

RESUMO

We assessed the fish assemblage structure and composition of Nova Ponte Reservoir (Araguari River, Upper Paraná Basin, Brazil). We observed significant differences in abundance (p = 0.0003), richness (p = 0.0005) and diversity (p = 0.02) between lacustrine and riverine zones of the reservoir. Nine species were significantly more abundant in the riverine region: Astyanax altiparanae, Astyanax gr. fasciatus, Galeocharax knerii, Hoplias intermedius, Hypostomus sp., Leporinus friderici, Leporinus obtusidens, Pimelodus maculatus and Schizodon nasutus. The results indicated a longitudinal gradient in the composition and abundance of fishes in Nova Ponte Reservoir, reinforcing the importance of freely flowing riverine reaches for conserving native neotropical ichthyofauna and reflecting the strong adaptation of these species to riverine systems.

Assuntos

RESUMO

Abstract We assessed the fish assemblage structure and composition of Nova Ponte Reservoir (Araguari River, Upper Paraná Basin, Brazil). We observed significant differences in abundance (p = 0.0003), richness (p = 0.0005) and diversity (p = 0.02) between lacustrine and riverine zones of the reservoir. Nine species were significantly more abundant in the riverine region: Astyanax altiparanae, Astyanax gr. fasciatus, Galeocharax knerii, Hoplias intermedius, Hypostomus sp., Leporinus friderici, Leporinus obtusidens, Pimelodus maculatus and Schizodon nasutus. The results indicated a longitudinal gradient in the composition and abundance of fishes in Nova Ponte Reservoir, reinforcing the importance of freely flowing riverine reaches for conserving native neotropical ichthyofauna and reflecting the strong adaptation of these species to riverine systems.

Resumo Este estudo avaliou a assembléia de peixes do reservatório de Nova Ponte (rio Araguari, bacia do Alto Paraná, Brasil), em termos de estrutura e composição. Foram observadas diferenças significativas na abundância (p = 0.0003), riqueza (p = 0.0005) e diversidade (p = 0.02) entre as zonas lacustres e fluviais do reservatório. Nove espécies foram mais abundantes na região fluvial: Astyanax altiparanae, Astyanax gr. fasciatus, Galeocharax knerii, Hoplias intermedius, Hypostomus sp., Leporinus friderici, Leporinus obtusidens, Pimelodus maculatus and Schizodon nasutus. Os resultados indicaram a existência de um gradiente longitudinal na composição e abundância de peixes no reservatório de Nova Ponte. Estes padrões reforçam a importância de trechos fluviais livres de barramentos para a conservação da ictiofauna neotropical nativa e refletem a forte adaptação dessas espécies aos sistemas fluviais.

Assuntos

RESUMO

Abstract We assessed the fish assemblage structure and composition of Nova Ponte Reservoir (Araguari River, Upper Paraná Basin, Brazil). We observed significant differences in abundance (p = 0.0003), richness (p = 0.0005) and diversity (p = 0.02) between lacustrine and riverine zones of the reservoir. Nine species were significantly more abundant in the riverine region: Astyanax altiparanae, Astyanax gr. fasciatus, Galeocharax knerii, Hoplias intermedius, Hypostomus sp., Leporinus friderici, Leporinus obtusidens, Pimelodus maculatus and Schizodon nasutus. The results indicated a longitudinal gradient in the composition and abundance of fishes in Nova Ponte Reservoir, reinforcing the importance of freely flowing riverine reaches for conserving native neotropical ichthyofauna and reflecting the strong adaptation of these species to riverine systems.(AU)

Resumo Este estudo avaliou a assembléia de peixes do reservatório de Nova Ponte (rio Araguari, bacia do Alto Paraná, Brasil), em termos de estrutura e composição. Foram observadas diferenças significativas na abundância (p = 0.0003), riqueza (p = 0.0005) e diversidade (p = 0.02) entre as zonas lacustres e fluviais do reservatório. Nove espécies foram mais abundantes na região fluvial: Astyanax altiparanae, Astyanax gr. fasciatus, Galeocharax knerii, Hoplias intermedius, Hypostomus sp., Leporinus friderici, Leporinus obtusidens, Pimelodus maculatus and Schizodon nasutus. Os resultados indicaram a existência de um gradiente longitudinal na composição e abundância de peixes no reservatório de Nova Ponte. Estes padrões reforçam a importância de trechos fluviais livres de barramentos para a conservação da ictiofauna neotropical nativa e refletem a forte adaptação dessas espécies aos sistemas fluviais.(AU)

Assuntos

RESUMO

Abstract We assessed the fish assemblage structure and composition of Nova Ponte Reservoir (Araguari River, Upper Paraná Basin, Brazil). We observed significant differences in abundance (p = 0.0003), richness (p = 0.0005) and diversity (p = 0.02) between lacustrine and riverine zones of the reservoir. Nine species were significantly more abundant in the riverine region: Astyanax altiparanae, Astyanax gr. fasciatus, Galeocharax knerii, Hoplias intermedius, Hypostomus sp., Leporinus friderici, Leporinus obtusidens, Pimelodus maculatus and Schizodon nasutus. The results indicated a longitudinal gradient in the composition and abundance of fishes in Nova Ponte Reservoir, reinforcing the importance of freely flowing riverine reaches for conserving native neotropical ichthyofauna and reflecting the strong adaptation of these species to riverine systems.

Resumo Este estudo avaliou a assembléia de peixes do reservatório de Nova Ponte (rio Araguari, bacia do Alto Paraná, Brasil), em termos de estrutura e composição. Foram observadas diferenças significativas na abundância (p = 0.0003), riqueza (p = 0.0005) e diversidade (p = 0.02) entre as zonas lacustres e fluviais do reservatório. Nove espécies foram mais abundantes na região fluvial: Astyanax altiparanae, Astyanax gr. fasciatus, Galeocharax knerii, Hoplias intermedius, Hypostomus sp., Leporinus friderici, Leporinus obtusidens, Pimelodus maculatus and Schizodon nasutus. Os resultados indicaram a existência de um gradiente longitudinal na composição e abundância de peixes no reservatório de Nova Ponte. Estes padrões reforçam a importância de trechos fluviais livres de barramentos para a conservação da ictiofauna neotropical nativa e refletem a forte adaptação dessas espécies aos sistemas fluviais.

RESUMO

The choice of sampling gears to assess benthic macroinvertebrate communities depends on environmental characteristics, study objectives, and cost effectiveness. Because of the high foraging capacity and diverse habitats and behaviors of benthophagous fishes, their stomach contents may offer a useful sampling tool in studies of benthic macroinvertebrates, especially in large, deep, fast rivers that are difficult to sample with traditional sediment sampling gear. Our objective was to compare the benthic macroinvertebrate communities sampled from sediments with those sampled from fish stomachs. We collected benthic macroinvertebrates and fish from three different habitat types (backwater, beach, riffle) in the wet season, drying season, and dry season along a single reach of the Grande River (Paraná River Basin, southeast Brazil). We sampled sediments through use of a Petersen dredge (total of 216 grabs) and used gill nets to sample fish (total of 36 samples). We analyzed the stomach contents of three commonly occurring benthophagous fish species (Eigenmannia virescens, Iheringichthys labrosus, Leporinus amblyrhynchus). Chironomids dominated in both sampling methods. Macroinvertebrate taxonomic composition and abundances from fish stomachs differed from those from sediment samples, but less so from riffles than from backwater and beach habitats. Macroinvertebrate taxa from E. virescens stomachs were more strongly correlated with sediment samples from all three habitats than were those from the other two species. The species accumulation curves and higher mean dispersion values, compared with with sediment samples suggest that E. virescens is more efficient than sediment samples and the other fish studied at collecting benthic taxa. We conclude that by analyzing the stomach contents of benthophagous fishes it is possible to assess important characteristics of benthic communities (dispersion, taxonomic composition and diversity). This is especially true for studies that only sample fish assemblages to evaluate aquatic ecosystem impacts. Therefore, this approach can be useful to amplify assessments of human impacts, and to incorporate additional bioindicators.

Assuntos

RESUMO

The choice of sampling gears to assess benthic macroinvertebrate communities depends on environmental characteristics, study objectives, and cost effectiveness. Because of the high foraging capacity and diverse habitats and behaviors of benthophagous fishes, their stomach contents may offer a useful sampling tool in studies of benthic macroinvertebrates, especially in large, deep, fast rivers that are difficult to sample with traditional sediment sampling gear. Our objective was to compare the benthic macroinvertebrate communities sampled from sediments with those sampled from fish stomachs. We collected benthic macroinvertebrates and fish from three different habitat types (backwater, beach, riffle) in the wet season, drying season, and dry season along a single reach of the Grande River (Paraná River Basin, southeast Brazil). We sampled sediments through use of a Petersen dredge (total of 216 grabs) and used gill nets to sample fish (total of 36 samples). We analyzed the stomach contents of three commonly occurring benthophagous fish species (Eigenmannia virescens, Iheringichthys labrosus, Leporinus amblyrhynchus). Chironomids dominated in both sampling methods. Macroinvertebrate taxonomic composition and abundances from fish stomachs differed from those from sediment samples, but less so from riffles than from backwater and beach habitats. Macroinvertebrate taxa from E. virescens stomachs were more strongly correlated with sediment samples from all three habitats than were those from the other two species. The species accumulation curves and higher mean dispersion values, compared with with sediment samples suggest that E. virescens is more efficient than sediment samples and the other fish studied at collecting benthic taxa. We conclude that by analyzing the stomach contents of benthophagous fishes it is possible to assess important characteristics of benthic communities (dispersion, taxonomic composition and diversity). This is especially true for studies that only sample fish assemblages to evaluate aquatic ecosystem impacts. Therefore, this approach can be useful to amplify assessments of human impacts, and to incorporate additional bioindicators.(AU)

A escolha da ferramenta adequada para avaliar as comunidades de macroinvertebrados bentônicos depende dos objetivos do estudo, das características ambientais e dos recursos financeiros disponíveis. Devido à alta capacidade de forrageamento apresentada por espécies de peixes bentófagas e seu acesso a diversos tipos de habitats, a análise do conteúdo estomacal destas espécies pode ser uma ferramenta útil em avaliações de assembleias de macroinvertebrados bentônicos, especialmente em rios grandes, profundos e rápidos, que são difíceis de amostrar através de métodos convencionais de coleta de sedimento. Nosso objetivo foi comparar as assembleias de macroinvertebrados bentônicos amostrados no sedimento com as assembleias amostradas nos estômagos de espécies de peixes bentófagas. Foram coletados peixes e sedimento em três diferentes tipos de habitats (remanso, praia, corredeira) nos períodos úmido e seco ao longo de um único trecho do rio Grande (bacia do rio Paraná, sudeste do Brasil). O sedimento foi amostrado através de uma draga Petersen (total de 216 dragas) e os peixes através de redes de emalhar (total de 36 amostras). Foram analisados os conteúdos estomacais de três espécies de peixes (Eigenmannia virescens Gymnotiformes, Iheringichthys labrosus Siluriformes; Leporinus amblyrhynchus Characiformes). Chironomidae foi a família dominante em ambos os métodos. A composição taxonômica de macroinvertebrados bentônicos encontrados nos estômagos foi diferente daquela amostrada no sedimento. Os taxa de macroinvertebrados amostrados nos estômagos de E. virescens foram mais correlacionados com os três tipos de habitats do que os taxa obtidos nos estômagos das outras duas espécies. As inclinações das curvas cumulativas, assim como os maiores valores de dispersão média, demonstram que E. virescens possui potencial como ferramenta ecológica para acessar as assembleias de macroinvertebrados bentônicos, assim como os maiores valores de dispersão observados. A família Philopotamidae foi encontrada apenas no estômago de L. amblyrhynchus. Concluímos que através da análise do conteúdo do estômago de peixes é possível acessar importantes características das assembleias bentônicas (p.ex. dispersão, composição taxonômica e diversidade). Esta abordagem é especialmente verdadeira em estudos que utilizam apenas as assembleias de peixes para avaliar e/ou monitorar ecossistemas aquáticos. Desta maneira, esse enfoque pode ser útil, aumentando o conhecimento acerca dos impactos humanos sobre os ecossistemas aquáticos e contribuindo para a utilização de diferentes grupos de bioindicadores.(AU)

Assuntos

RESUMO

Successive daily peak flows from hydropower plants can disrupt aquatic ecosystems and alter the composition and structure of macroinvertebrates downstream. We evaluated the influence of peak flow changes on macroinvertebrate drift downstream of a hydroelectric plant as a basis for determining ecological flows that might reduce the disturbance of aquatic biota. The aim of this study was to assess the influence of flow fluctuations on the seasonal and daily drift patterns of macroinvertebrates. We collected macroinvertebrates during fixed flow rates (323 m3.s1 in the wet season and 111 m3.s1 in the dry season) and when peak flows fluctuated (378 to 481 m3.s1 in the wet season, and 109 to 173 m3.s1 in the dry season) in 2010. We collected 31,924 organisms belonging to 46 taxa in the four sampling periods. Taxonomic composition and densities of drifting invertebrates differed between fixed and fluctuating flows, in both wet and dry seasons, but family richness varied insignificantly. We conclude that macroinvertebrate assemblages downstream of dams are influenced by daily peak flow fluctuations. When making environmental flow decisions for dams, it would be wise to consider drifting macroinvertebrates because they reflect ecological changes in downstream biological assemblages.

Os sucessivos pulsos diários de vazão decorrentes da operação de usinas hidrelétricas podem perturbar os ecossistemas aquáticos e alterar a composição e estrutura de macroinvertebrados a jusante de barramentos. Nós avaliamos a influência de alterações de vazão sobre a deriva de macroinvertebrados a jusante de uma barragem hidrelétrica como subsídio para a determinação de vazões ecológicas que podem reduzir os distúrbios sobre a biota aquática. O objetivo deste estudo foi avaliar a influência das flutuações de vazão sobre os padrões sazonais e diários de deriva de macroinvertebrados. Nós coletamos os macroinvertebrados durante períodos de vazão fixa (323 m3.s1 na estação de chuvas e 111 m3.s1 na estação seca) e com flutuações de vazão (378 - 481 m3.s1 na estação de chuvas e 109 - 173 m3.s1 na estação seca) no ano de 2010. Foram coletados 31.924 organismos distribuídos em 46 taxa nos quatro períodos amostrais. A composição taxonômica e a densidade de invertebrados a deriva diferiram entre os períodos com vazão fixa e flutuante, tanto na estação de chuvas quanto na seca, mas a riqueza taxonômica não variou significativamente. Em conclusão, as comunidades de macroinvertebrados a jusante de barragens são influenciadas pelas flutuações diárias na vazão. Portanto, os macroinvertebrados a deriva devem ser considerados nos cálculos de vazões ambientais, pois eles claramente refletem as mudanças ecológicas nas comunidades biológicas a jusante de barragens hidrelétricas.

Assuntos

RESUMO

Successive daily peak flows from hydropower plants can disrupt aquatic ecosystems and alter the composition and structure of macroinvertebrates downstream. We evaluated the influence of peak flow changes on macroinvertebrate drift downstream of a hydroelectric plant as a basis for determining ecological flows that might reduce the disturbance of aquatic biota. The aim of this study was to assess the influence of flow fluctuations on the seasonal and daily drift patterns of macroinvertebrates. We collected macroinvertebrates during fixed flow rates (323 m3.s1 in the wet season and 111 m3.s1 in the dry season) and when peak flows fluctuated (378 to 481 m3.s1 in the wet season, and 109 to 173 m3.s1 in the dry season) in 2010. We collected 31,924 organisms belonging to 46 taxa in the four sampling periods. Taxonomic composition and densities of drifting invertebrates differed between fixed and fluctuating flows, in both wet and dry seasons, but family richness varied insignificantly. We conclude that macroinvertebrate assemblages downstream of dams are influenced by daily peak flow fluctuations. When making environmental flow decisions for dams, it would be wise to consider drifting macroinvertebrates because they reflect ecological changes in downstream biological assemblages.(AU)

Os sucessivos pulsos diários de vazão decorrentes da operação de usinas hidrelétricas podem perturbar os ecossistemas aquáticos e alterar a composição e estrutura de macroinvertebrados a jusante de barramentos. Nós avaliamos a influência de alterações de vazão sobre a deriva de macroinvertebrados a jusante de uma barragem hidrelétrica como subsídio para a determinação de vazões ecológicas que podem reduzir os distúrbios sobre a biota aquática. O objetivo deste estudo foi avaliar a influência das flutuações de vazão sobre os padrões sazonais e diários de deriva de macroinvertebrados. Nós coletamos os macroinvertebrados durante períodos de vazão fixa (323 m3.s1 na estação de chuvas e 111 m3.s1 na estação seca) e com flutuações de vazão (378 - 481 m3.s1 na estação de chuvas e 109 - 173 m3.s1 na estação seca) no ano de 2010. Foram coletados 31.924 organismos distribuídos em 46 taxa nos quatro períodos amostrais. A composição taxonômica e a densidade de invertebrados a deriva diferiram entre os períodos com vazão fixa e flutuante, tanto na estação de chuvas quanto na seca, mas a riqueza taxonômica não variou significativamente. Em conclusão, as comunidades de macroinvertebrados a jusante de barragens são influenciadas pelas flutuações diárias na vazão. Portanto, os macroinvertebrados a deriva devem ser considerados nos cálculos de vazões ambientais, pois eles claramente refletem as mudanças ecológicas nas comunidades biológicas a jusante de barragens hidrelétricas.(AU)

Assuntos

RESUMO

Successive daily peak flows from hydropower plants can disrupt aquatic ecosystems and alter the composition and structure of macroinvertebrates downstream. We evaluated the influence of peak flow changes on macroinvertebrate drift downstream of a hydroelectric plant as a basis for determining ecological flows that might reduce the disturbance of aquatic biota. The aim of this study was to assess the influence of flow fluctuations on the seasonal and daily drift patterns of macroinvertebrates. We collected macroinvertebrates during fixed flow rates (323 m3.s-1 in the wet season and 111 m3.s-1 in the dry season) and when peak flows fluctuated (378 to 481 m3.s-1 in the wet season, and 109 to 173 m3.s-1 in the dry season) in 2010. We collected 31,924 organisms belonging to 46 taxa in the four sampling periods. Taxonomic composition and densities of drifting invertebrates differed between fixed and fluctuating flows, in both wet and dry seasons, but family richness varied insignificantly. We conclude that macroinvertebrate assemblages downstream of dams are influenced by daily peak flow fluctuations. When making environmental flow decisions for dams, it would be wise to consider drifting macroinvertebrates because they reflect ecological changes in downstream biological assemblages.

Assuntos