Fish biomarker responses reflect landscape anthropic disturbance in savanna streams.

Disturbance in the landscape surrounding streams can interfere with water quality and cause harm to aquatic organisms. In this study, we evaluate the influence of land use on the genetic and biochemical biomarkers of fish in streams of Brazilian savanna (Cerrado). We also evaluated whether biomarker responses are seasonally consistent. For this purpose, individuals of the Neotropical tetra fish Astyanax lacustris were exposed in cages for 96 h, in 13 streams draining agroecosystems with different degrees of disturbance during the dry and wet seasons. After exposure, blood, liver, and gills were collected for multibiomarker analyses (micronuclei, erythrocytic nuclear abnormalities, lipid peroxidation, antioxidant enzymes, and biotransformation enzyme). The results showed that the gradient of anthropic disturbance was positively associated with genotoxic damage (erythrocytic nuclear abnormalities) and negatively associated with antioxidant and biotransformation enzymes of the liver in both seasons. No association of the gradient of anthropic disturbance with the frequency of micronuclei and for most gill enzymes was found for both seasons. Landscape disturbance was also negatively associated with water quality in the wet season. These results indicate that changes in land use interfere with the genetic and biochemical processes of organisms. Thus, the multibiomarker approach may represent an effective strategy for assessing and monitoring terrestrial landscape disturbance.

Shortcuts for biomonitoring programs of stream ecosystems: Evaluating the taxonomic, numeric, and cross-taxa congruence in phytoplankton, periphyton, zooplankton, and fish assemblages.

Different biological groups can be used for monitoring aquatic ecosystems because they can respond to variations in the environment. However, the evaluation of different bioindicators may demand multiple financial resources and time, especially when abundance quantification and species-level identification are required. In this study, we evaluated whether taxonomic, numerical resolution and cross-taxa can be used to optimize costs and time for stream biomonitoring in Central Brazil (Cerrado biome). For this, we sampled different biological groups (fish, zooplankton, phytoplankton, and periphyton) in stream stretches distributed in a gradient of land conversion dominated by agriculture and livestock. We used the Mantel and Procrustes analyses to test the association among different taxonomic levels (species to class), the association between incidence and abundance data (numerical resolution), and biological groups. We also assessed the relative effect of local environmental and spatial predictors on different groups. The taxonomic levels and numerical resolutions were strongly correlated in all taxonomic groups (r > 0.70). We found no correlations among biological groups. Different sets of environmental variables were the most important to explain the variability in species composition of distinct biological groups. Thus, we conclude that monitoring the streams in this region using bioindicators is more informative through higher taxonomic levels with occurrence data than abundance. However, different biological groups provide complementary information, reinforcing the need for a multi-taxa approach in biomonitoring.

Broad and fine-scale threats on threatened Brazilian freshwater fish: variability across hydrographic regions and taxonomic groups / Ameaças em ampla e fina escala sobre peixes de água doce ameaçados de extinção do Brasil: variabilidade entre regiões hidrográficas e grupos taxonômicos

Abstract: Anthropogenic environmental changes are the main cause of species extinction during the Holocene. Species have been exposed to major source of threats, such as habitat loss and fragmentation, pollution, introduced species, and harvesting, many of which are derived from specific anthropogenic activities, such as urbanization, agriculture, and damming (i.e. fine-scale threats). However, the importance of these threats on the species conservation status in a given region depends on the type of impacts they are exposed to and the susceptibility of species to these impacts. In this study, we used a database of threatened Brazilian freshwater fish species to test whether the major source of threats and the specific anthropogenic impacts to species vary across hydrographic regions and taxonomic groups. Our results showed that habitat loss is a ubiquitous major threat jeopardizing the conservation status of the Brazilian fish species. However, different fine-scale threats mediate this process across hydrographic regions and taxonomic groups. The combination of impacts from agriculture, deforestation, and urbanization affects most of the threatened species in the basins of the Northeast, South, and Southeast, including the species of the most threatened order, the Cyprinodontiformes. Damming is the main human activity affecting threatened species of Siluriformes, Characiformes, Gymnotiformes, and Cichliformes, especially in northern basins (Amazon and Tocantins-Araguaia). Therefore, we found that specific fine-scale threats influencing threatened species vary across hydrographic regions and taxonomic groups, probably due to geographic variability in the incidence of human activities and differential niche requirements and vulnerability of species to these activities.

Resumo: Alterações ambientais antropogênicas são a principal causa de extinção das espécies no Holoceno. As espécies têm sido expostas à diferentes fontes de ameaças principais, tais como a perda e fragmentação de habitat, poluição, introdução de espécies e coleta de organismos, muitas das quais são decorrentes de atividades antropogênicas específicas, tais como urbanização, agricultura e represamento (i.e. ameaças de escala fina). Entretanto, a importância dessas ameaças no estado de conservação das espécies em uma dada região depende do tipo de ameaça que as espécies são expostas e da susceptibilidade das espécies a esses impactos. Neste estudo, utilizamos a base de dados de espécies de peixes dulcícolas do Brasil ameaçadas de extinção para testar se as principais ameaças e os impactos específicos às espécies variam entre as regiões hidrográficas e grupos taxonômicos. Nossos resultados mostraram que a perda de habitat é uma ameaça principal ubíqua, prejudicando o estado de conservação das espécies de peixes do Brasil. Entretanto, diferentes ameaças de escala mais fina mediam este processo entre a regiões hidrográficas e grupos taxonômicos. A combinação de impactos provenientes da agricultura, desmatamento e urbanização afeta a maior parte das espécies ameaçadas nas bacias do Nordeste, Sul e Sudeste, incluindo as espécies da ordem mais ameaçada, os Cyprinodontiformes. O represamento dos rios é a principal atividade humana afetando as espécies ameaçadas de Siluriformes, Characiformes, Gymnotiformes e Cichliformes, especialmente nas bacias do norte (Amazônica e Tocantins-Araguaia). Portanto, as ameaças em escala fina que afetam as espécies ameaçadas variam entre as regiões hidrográficas e grupos taxonômicos, provavelmente devido à variabilidade geográfica na incidência das atividades de impacto humano e em função das diferenças nos requerimentos de nicho e vulnerabilidade das espécies a essas atividades.

Stream fish metacommunity organisation across a Neotropical ecoregion: The role of environment, anthropogenic impact and dispersal-based processes.

Understanding how assemblages are structured in space and the factors promoting their distributions is one of the main goals in Ecology, however, studies regarding the distribution of organisms at larger scales remain biased towards terrestrial groups. We attempt to understand if the structure of stream fish metacommunities across a Neotropical ecoregion (Upper Paraná-drainage area of 820,000 km2) are affected by environmental variables, describing natural environmental gradient, anthropogenic impacts and spatial predictors. For this, we obtained 586 sampling points of fish assemblages in the ecoregion and data on environmental and spatial predictors that potentially affect fish assemblages. We calculated the local beta diversity (Local Contribution to Beta Diversity, LCBD) and alpha diversity from the species list, to be used as response variables in the partial regression models, while the anthropogenic impacts, environmental gradient and spatial factors were used as predictors. We found a high total beta diversity for the ecoregion (0.41) where the greatest values for each site sampled were located at the edges of the ecoregion, while richer communities were found more centrally. All sets of predictors explained the LCBD and alpha diversity, but the most important was dispersal variables, followed by the natural environmental gradient and anthropogenic impact. However, we found an increase in the models' prediction power through the shared effect. Results suggest that environmental filters (i.e. environmental variables such as climate, hydrology and anthropogenic impact) and dispersal limitation together shape fish assemblages of the Upper Paraná ecoregion, showing the importance of using multiple sets of predictors to understand the processes structuring biodiversity distribution.

Fish biomarker responses to perturbation by drought in streams

Drought can be viewd as a perturbation in running waters and fish are often trapped in isolated pools, where deterioration of water quality may be stressful. We investigated how this extreme condition influences response of oxidative stress biomarkers. The response of the characid Astyanax elachylepis was assessed during the dry and rainy seasons in intermittent and perennial (control) sites in streams from Brazilian savannah (Cerrado). We predicted that the biomarkers would be enhanced in the dry season in intermittent streams only due the environmentally harsh conditions in the few isolated pools that remain filled with water. As predicted, fish from the intermittent stream in the dry season presented higher gill MDA values, indicating greater stress. In the liver, MDA values were higher in the dry season for both intermittent and perennial streams, suggesting a generalized seasonal response. As expected, some antioxidant response enzymes changed in the intermittent sites during the dry season. Therefore, oxidative stress biomarkers vary seasonally, with greater increase in intermittent sites. These evidences contribute for the understanding of the spatio-temporal variation of the fish responses and fish resistance to perturbations by drought in tropical environments.(AU)

A seca pode ser vista como uma perturbação em ambientes aquáticos lóticos e, em alguns casos, os peixes podem ser aprisionados em trechos lênticos (poços), onde a perda da qualidade da água pode causar estresse. Investigamos como esta condição extrema influencia biomarcadores bioquímicos de estresse oxidativo. Para isso, a resposta do caracídeo Astyanax elachylepis foi avaliada durante as estações seca e chuvosa em trechos intermitentes e perenes (controle) de riachos da savana brasileira (Cerrado). Predizemos que os biomarcadores seriam aumentados somente em peixes dos trechos intermitentes durante a estação seca, devido as condições restritivas dos poucos poços isolados que contém água. Como predito, os peixes do riacho intermitente apresentaram altos valores de MDA nas brânquias durante a estação seca, indicando maior estresse oxidativo. No fígado, os valores de MDA foram maiores na estação seca em ambos riachos, intermitente e perene, sugerindo uma resposta sazonal generalizada. Como esperado, algumas enzimas antioxidantes foram alteradas em peixes de trechos intermitentes durante a estação seca. Portanto, os biomarcadores de estresse oxidativo variam sazonalmente e essa variação é maior em trechos intermitentes. Essas evidências contribuem para a compreensão da variação espaço-temporal da resposta dos peixes e da sua resistência às perturbações por seca em ambientes tropicais.(AU)

Short-term response of fish assemblages to instream habitat restoration in heavily impacted streams

Habitat homogenization has been a major impact in stream ecosystems, and it is considered one of the main drivers of biotic homogenization as well, leading to the loss of water quality and fish diversity. In this study, we added artificial woody structures and leaf packs in physically impacted streams to test if the additions can improve habitat complexity and change the taxonomic and functional structure of fish communities. The experiment was done in eight streams impacted by siltation, deforestation, and habitat homogeneization, inserted in an agricultural landscape from the Upper Paraná River Basin, and lasted 112 days. The provision of artificial microhabitats increased instream habitat diversity by creating patches of organic matter deposits, changing flow, and providing substrate for grass colonization of the instream habitat. The experimental manipulation also changed fish species abundance. Nine species contributed to these changes, five decreased and four increased in abundance, indicating species responded differently to the experimental manipulation. However, overall species richness, diversity, and community functional traits remained unaltered. These results indicate that short-term habitat restoration on a local scale may not be enough to promote changes in fish community attributes of streams that are heavily impacted.(AU)

A homogeneização de habitats tem sido um importante impacto nos ecossistemas de riachos e também é considerada um dos principais fatores de homogeneização biótica, levando à perda da qualidade da água e da diversidade de peixes. Neste estudo, adicionamos estruturas artificiais de madeira e pacotes de folhas em riachos fisicamente impactados para testar se as adições podem aumentar a heterogeneidade do habitat e alterar a estrutura taxonômica e funcional das comunidades de peixes. O experimento foi realizado em oito riachos impactados por assoreamento, desmatamento e homogeneização de hábitat, inseridos em uma paisagem agrícola da bacia do Alto Paraná, com duração de 112 dias. O fornecimento de microhabitats artificiais aumentou a diversidade de hábitat criando manchas de depósitos de matéria orgânica, alterando o fluxo e fornecendo substrato para a colonização de grama no interior do canal. A manipulação experimental também alterou a abundância de espécies de peixes. Dentre as nove espécies que contribuíram para essas alterações, cinco diminuíram e quatro aumentaram em abundância, indicando que as espécies responderam diferentemente à manipulação experimental. No entanto, a riqueza geral de espécies, a diversidade e as características funcionais da comunidade permaneceram inalteradas. Esses resultados indicam que a restauração de habitat a curto prazo em escala local pode não ser suficiente para promover mudanças nos atributos da comunidade de córregos que são fortemente impactados.(AU)

Short-term response of fish assemblages to instream habitat restoration in heavily impacted streams

Habitat homogenization has been a major impact in stream ecosystems, and it is considered one of the main drivers of biotic homogenization as well, leading to the loss of water quality and fish diversity. In this study, we added artificial woody structures and leaf packs in physically impacted streams to test if the additions can improve habitat complexity and change the taxonomic and functional structure of fish communities. The experiment was done in eight streams impacted by siltation, deforestation, and habitat homogeneization, inserted in an agricultural landscape from the Upper Paraná River Basin, and lasted 112 days. The provision of artificial microhabitats increased instream habitat diversity by creating patches of organic matter deposits, changing flow, and providing substrate for grass colonization of the instream habitat. The experimental manipulation also changed fish species abundance. Nine species contributed to these changes, five decreased and four increased in abundance, indicating species responded differently to the experimental manipulation. However, overall species richness, diversity, and community functional traits remained unaltered. These results indicate that short-term habitat restoration on a local scale may not be enough to promote changes in fish community attributes of streams that are heavily impacted.(AU)

A homogeneização de habitats tem sido um importante impacto nos ecossistemas de riachos e também é considerada um dos principais fatores de homogeneização biótica, levando à perda da qualidade da água e da diversidade de peixes. Neste estudo, adicionamos estruturas artificiais de madeira e pacotes de folhas em riachos fisicamente impactados para testar se as adições podem aumentar a heterogeneidade do habitat e alterar a estrutura taxonômica e funcional das comunidades de peixes. O experimento foi realizado em oito riachos impactados por assoreamento, desmatamento e homogeneização de hábitat, inseridos em uma paisagem agrícola da bacia do Alto Paraná, com duração de 112 dias. O fornecimento de microhabitats artificiais aumentou a diversidade de hábitat criando manchas de depósitos de matéria orgânica, alterando o fluxo e fornecendo substrato para a colonização de grama no interior do canal. A manipulação experimental também alterou a abundância de espécies de peixes. Dentre as nove espécies que contribuíram para essas alterações, cinco diminuíram e quatro aumentaram em abundância, indicando que as espécies responderam diferentemente à manipulação experimental. No entanto, a riqueza geral de espécies, a diversidade e as características funcionais da comunidade permaneceram inalteradas. Esses resultados indicam que a restauração de habitat a curto prazo em escala local pode não ser suficiente para promover mudanças nos atributos da comunidade de córregos que são fortemente impactados.(AU)

Fish biomarker responses to perturbation by drought in streams

ABSTRACT Drought can be viewd as a perturbation in running waters and fish are often trapped in isolated pools, where deterioration of water quality may be stressful. We investigated how this extreme condition influences response of oxidative stress biomarkers. The response of the characid Astyanax elachylepis was assessed during the dry and rainy seasons in intermittent and perennial (control) sites in streams from Brazilian savannah (Cerrado). We predicted that the biomarkers would be enhanced in the dry season in intermittent streams only due the environmentally harsh conditions in the few isolated pools that remain filled with water. As predicted, fish from the intermittent stream in the dry season presented higher gill MDA values, indicating greater stress. In the liver, MDA values were higher in the dry season for both intermittent and perennial streams, suggesting a generalized seasonal response. As expected, some antioxidant response enzymes changed in the intermittent sites during the dry season. Therefore, oxidative stress biomarkers vary seasonally, with greater increase in intermittent sites. These evidences contribute for the understanding of the spatio-temporal variation of the fish responses and fish resistance to perturbations by drought in tropical environments.

RESUMO A seca pode ser vista como uma perturbação em ambientes aquáticos lóticos e, em alguns casos, os peixes podem ser aprisionados em trechos lênticos (poços), onde a perda da qualidade da água pode causar estresse. Investigamos como esta condição extrema influencia biomarcadores bioquímicos de estresse oxidativo. Para isso, a resposta do caracídeo Astyanax elachylepis foi avaliada durante as estações seca e chuvosa em trechos intermitentes e perenes (controle) de riachos da savana brasileira (Cerrado). Predizemos que os biomarcadores seriam aumentados somente em peixes dos trechos intermitentes durante a estação seca, devido as condições restritivas dos poucos poços isolados que contém água. Como predito, os peixes do riacho intermitente apresentaram altos valores de MDA nas brânquias durante a estação seca, indicando maior estresse oxidativo. No fígado, os valores de MDA foram maiores na estação seca em ambos riachos, intermitente e perene, sugerindo uma resposta sazonal generalizada. Como esperado, algumas enzimas antioxidantes foram alteradas em peixes de trechos intermitentes durante a estação seca. Portanto, os biomarcadores de estresse oxidativo variam sazonalmente e essa variação é maior em trechos intermitentes. Essas evidências contribuem para a compreensão da variação espaço-temporal da resposta dos peixes e da sua resistência às perturbações por seca em ambientes tropicais.

High school students' knowledge of endangered fauna in the Brazilian Cerrado: A cross-species and spatial analysis.

The ability of high school students to know endangered species can vary among species (e.g., large body size can influence people's interest) or among municipalities (e.g., more contact with biodiversity can influence people's interest). Thus, in the present paper, we evaluated high school students' knowledge about the endangered and non-endangered mammalian species of the Brazilian Cerrado. We tested whether the recognition of the endangered and non-endangered species varied in a cross-species analysis (twelve total species) according to species characteristics, such as body size, popularity, endangered status and the length of time of inclusion on the endangered species list. Moreover, we tested whether the recognition of the endangered mammal species varied between municipalities (spatial analysis). We interviewed 366 students in their first year of high school in 21 schools (one in each municipality). Our results indicated that the proportion of correctly identified endangered species varied according to species (cross-species). The endangered species that were most often correctly identified were Myrmecophaga tridactyla (known by its popular name, Tamanduá-bandeira, in Brazil), Priodontes maximus (Tatu canastra) and Panthera onca (onça-pintada), with more than 80% correct answers. Thus, students tended to recognize the more popular species and the endangered species more than the non-endangered species. The analysis of student knowledge according to municipality demonstrated that the students' ability to recognize endangered species followed a spatial pattern. Finally, the cross-species and spatial variation patterns detected in the present study indicated the importance of formal education in increasing high school students' knowledge about endangered species and suggested that education should also promote less well-known species, species with smaller body sizes, and other groups of vertebrates and invertebrates and consider local and regional biodiversity whenever possible.

Seasonal and Site Differences in Phorid Parasitoidism Rates of Leaf-Cutting Ants.

Interspecific interactions are influenced by several environmental factors that may affect spatial and temporal dynamics. Seasonal variations in environmental conditions and differences among sites may affect the intensity of interactions and the abundance of interacting species. In this study, we describe the variability in parasitoids of Atta ants among sites and seasons over a year. More specifically, we studied parasitoidism of Atta sexdens Linnaeus and Atta laevigata Smith nests at a site with native cerrado vegetation and a Eucalyptus monoculture in dry and rainy seasons. Of the 45,147 workers collected, 1,020 (2.2%) were parasitized. We found five parasitoid species of A. sexdens and four species of A. laevigata. The two species of leaf-cutting ants shared similar parasitoid communities, but the infection rate was higher in A. laevigata (5.3%) compared with A. sexdens (0.8%). Parasitoidism rates of A. laevigata increased in the rainy season, but the rate for A. sexdens was consistently low in both seasons. The identity of the host species and the season, therefore, appear to interact to influence the rate of parasitoidism in these leaf-cutting ant species.

Isolated and mixed effects of diuron and its metabolites on biotransformation enzymes and oxidative stress response of Nile tilapia (Oreochromis niloticus).

Diuron is one of the most used herbicide in the world, and its field application has been particularly increased in Brazil due to the expansion of sugarcane crops. Diuron has often been detected in freshwater ecosystems and it can be biodegraded into three main metabolites in the environment, the 3,4-dichloroaniline (DCA), 3,4-dichlorophenylurea (DCPU) and 3,4-dichlorophenyl-N-methylurea (DCPMU). Negative effects under aquatic biota are still not well established for diuron, especially when considering its presence in mixture with its different metabolites. In this study, we evaluated the effects of diuron alone or in combination with its metabolites, DCPMU, DCPU and 3,4-DCA on biochemical stress responses and biotransformation activity of the fish Oreochromis niloticus. Results showed that diuron and its metabolites caused significant but dispersed alterations in oxidative stress markers and biotransformation enzymes, except for ethoxyresorufin-O-deethylase (EROD) activity, that presented a dose-dependent increase after exposure to either diuron or its metabolites. Glutathione S-transferase (GST) activity was significant lower in gills after exposure to diuron metabolites, but not diuron. Diuron, DCPMU and DCA also decreased the multixenobiotic resistance (MXR) activity. Lipid peroxidation levels were increased in gill after exposure to all compounds, indicating that the original compound and diuron metabolites can induce oxidative stress in fish. The integration of all biochemical responses by the Integrated Biomarker Response (IBR) model indicated that all compounds caused significant alterations in O. niloticus, but DCPMU caused the higher alterations in both liver and gill. Our findings imply that diuron and its metabolites may impair the physiological response related to biotransformation and antioxidant activity in fish at field concentrations. Such alterations could interfere with the ability of aquatic animals to adapt to environments contaminated by agriculture.

Trends and gaps of the scientific literature about the effects of fire on Brazilian Cerrado / Tendências e lacunas na literatura científica sobre os efeitos do fogo no Cerrado Brasileiro

Abstract Fire management is an important issue in the Brazilian Cerrado, since both anthropogenic high intensity fires and complete fire suppression can reduce the biodiversity in this biome. In this paper, we highlight the trends in scientific literature about fire effects in the Cerrado, aiming to detect possible gaps and to indicate directions of future scientific research. We searched for articles in the periodic database Web of Knowledge from 1991 to 2016, and observed an increase in the number of publications throughout the years. Most articles were associated with Brazilian institutions (58%), followed by those with collaboration between Brazilian and international institutions (33%), and those published by authors exclusively from international institutions (9%). Most articles addressed the effects of fire on biodiversity (77%), followed by articles about abiotic environment (19%), and then biotic interactions or interactions between organisms and environment (4%). The most studied taxonomic group was plants (75%), followed by mammals (8%) and insects (6%), with the remaining taxa comprising about 11% of publications. The Federal District was the federative unit with the greatest number of studies (31%). The majority of studies was conducted in areas with fewer fire events, whereas areas with major incidence of fires are poorly studied. Our data shows that studies on the effect of fires on the Brazilian Cerrado are geographically and taxonomically biased. This lack of knowledge limits the extrapolations about the effects of fire on this biome. Therefore, we emphasize the need for investment in research in areas with high fire frequency and also for an increase in knowledge about these effects on the biota, especially on the fauna. This action is fundamental to support the development of public policies for effective and directed fire management in the Cerrado.

Resumo O manejo do fogo é uma questão importante no Cerrado brasileiro, pois tanto os incêndios antropogênicos de alta intensidade, quanto a sua supressão completa podem reduzir a biodiversidade neste bioma. Neste artigo, destacamos as tendências na literatura científica sobre os efeitos do fogo no Cerrado, com o objetivo de detectar possíveis lacunas e indicar direções de futuras pesquisas científicas. Buscamos artigos na base de periódicos Web of Knowledge no período de 1991 a 2016, e observamos um aumento no número de publicações ao longo dos anos. A maioria dos artigos foi associada a instituições brasileiras (58%), seguidos por colaborações entre instituições brasileiras e internacionais (33%) e publicações de autores exclusivamente de instituições internacionais (9%). A maioria dos artigos abordou os efeitos do fogo na biodiversidade (77%), seguido de artigos sobre o ambiente abiótico (19%), e interações bióticas ou interações entre organismos e o ambiente (4%). O grupo taxonômico mais estudado foi plantas (75%), seguido de mamíferos (8%) e insetos (6%). Os táxons restantes incluem 11% das publicações. O Distrito Federal foi a unidade federativa com o maior número de estudos (31%). A maioria dos estudos foi realizada em áreas com menos queimadas, enquanto as áreas com maior incidência de fogo são mal estudadas. Nossos dados mostram que os estudos sobre o efeito do fogo no Cerrado brasileiro são enviesados do ponto de vista geográfico e taxonômico. Esta falta de conhecimento limita as extrapolações sobre o efeito do fogo neste bioma. Portanto, enfatizamos a necessidade de investimentos para pesquisas em áreas com alta freqüência de queimadas e a necessidade em aumentar o conhecimento sobre estes efeitos na biota, especialmente na fauna. Esta ação é fundamental para apoiar o desenvolvimento de políticas públicas para uma gestão efetiva e direcionada do fogo no Cerrado.

Influence of temperature on the antioxidant responses and lipid peroxidation of two species of tadpoles (Rhinella schneideri and Physalaemus nattereri) exposed to the herbicide sulfentrazone (Boral 500SC®).

Amphibians can experience large temperature fluctuations in their habitats, especially during the larval stage, when tadpoles are restricted to small and ephemeral ponds. Changes in water temperature can alter development, metabolism and behaviour of cold-blooded animals but also the toxicokinetics of chemicals in the environment. In Brazil, pesticides application is intensified during the rainy season, which is the period of reproduction for many amphibian species. We evaluated here the influence of temperature (28, 32, and 36°C) on the toxicity of the herbicide sulfentrazone (Boral®SC) in tadpoles of Physalaemus nattereri and Rhinella schneideri, by analysis of oxidative stress biomarkers. Exposure of tadpoles to sulfentrazone altered the antioxidant enzymes activities and induced lipid peroxidation with temperature-associated responses. Catalase, superoxide dismutase and glucose-6-phosphate dehydrogenase (G6PDH) were impaired by combined effect of temperature and sulfentrazone in both species. G6PDH was increased in most groups exposed to 36°C. Biotransformation enzyme glutathione-S-transferase had more evident alterations in P. nattereri at higher temperatures and changes in tGSH contents presented different patterns between the species. Lipid peroxidation was particularly induced in tadpoles of P. nattereri. Integrated biomarker response (IBR) index indicated a synergic effect of temperature and sulfentrazone for tadpoles of P. nattereri, while the IBR was mainly influenced by temperature in R. schneideri. Our study showed that temperature modulates biochemical responses in tadpoles exposed to sulfentrazone with a species-specific pattern. These findings imply that the effects of abiotic factors should be taken into account to evaluate the real risks of exposure of amphibians to commonly used pesticides.

Use of functional traits to assess changes in stream fish assemblages across a habitat gradient

Functional traits are important for understanding the links between species occurrence and environmental conditions. Identifying these links makes it possible to predict changes in species composition within communities under specific environmental conditions. We used functional traits related to habitat use and trophic ecology in order to assess the changes in fish community composition between streams with varying habitat structure. The relationship between the species traits and habitat characteristics was analyzed using an RLQ ordination analysis. Although species were widely distributed in habitats with different structures, physical conditions did favor some species based on their functional characteristics. Eight functional traits were found to be associated with stream habitat structure, allowing us to identify traits that may predict the susceptibility of fish species to physical habitat degradation.

Os atributos funcionais são importantes para entender a ligação entre ocorrência das espécies e condições ambientais, permitindo predizer sobre as mudanças na composição de espécies em comunidades submetidas a condições ambientais específicas. Utilizamos atributos funcionais relacionados com o uso de habitat e ecologia trófica para avaliar as mudanças na composição de espécies de peixes em riachos com diferenças na estrutura física. O relacionamento entre os atributos das espécies e as variáveis ambientais foi avaliado por meio da análise de ordenação RLQ. Embora algumas espécies tenham sido amplamente distribuídas em hábitats com diferentes características, outras foram restritas por essas condições e este relacionamento está associado com as características morfológicas. Oito atributos funcionais foram capazes de detectar as variações na estrutura física do hábitat em riachos, permitindo a identificação de atributos que podem predizer a suscetibilidade das espécies de peixes para a degradação física do hábitat.

Environmental constraints structuring fish assemblages in riffles: evidences from a tropical stream

ABSTRACT Riffles are unique habitats regarding to assemblage structure. However, understanding how these assemblages respond to environmental variations in small spatial extents, as within a stream, is a challenge. We assess whether the quantitative structure and the trophic composition of fish assemblages vary predictably among stream riffles. We predict that the variation of environmental conditions will explain species abundance and trophic composition, with the latter presenting higher predictive power, since species would be filtered according to their traits (e.g. diet). Moreover, we expect that the low among-riffle dispersal limitation within a stream and the strong habitat filtering would result in lower importance of spatial variables in the structure of riffle fish assemblages. We tested these predictions by studying 18 riffles of a stream in the Central Brazil. Environmental variables, but not spatial ones, were the most important in explaining the variation in assemblages structure. Environmental variables explained a greater portion of the trophic structure variation (R2=0.62) than of abundance (R2=0.37), indicating that the variation on the trophic traits at community level are more predictable. These results also indicate that these assemblages are subject to environmental control, highlighting the importance of riffle characteristics in driving ecological processes within streams.

RESUMO Corredeiras são habitats singulares no que se refere à estrutura das suas assembleias. Entretanto, a compreensão sobre como essas assembleias respondem às variações ambientais em pequenas extensões espaciais, como dentro de um riacho, ainda é um desafio. Avaliamos se a estrutura quantitativa das assembleias de peixes, assim como a sua composição trófica variam previsivelmente entre corredeiras de riachos. Predizemos que a variação nas condições ambientais explicará a abundância das espécies, assim como a sua composição trófica, entretanto, com uma maior proporção da variação explicada para a segunda, já que as espécies seriam filtradas de acordo com seus atributos (e.g. dieta). Além disso, esperamos que a pequena limitação para a dispersão entre as corredeiras de um mesmo riacho, associada à forte filtragem ambiental, resultaria em uma menor importância de variáveis espaciais na estruturação das assembleias de corredeiras. Para testar essas predições, estudamos 18 corredeiras de um rio do Brasil Central. As variáveis ambientais, e não as espaciais, foram mais importantes para explicar a variação na estrutura das assembleias. As variáveis ambientais explicaram uma maior proporção da variação da composição trófica (R2=0,62), em comparação com a abundância (R2=0,37), indicando maior previsibilidade na variação dos atributos relacionados a dieta em nível de comunidade. Esses resultados também indicam que essas assembleias são sujeitas a forte controle ambiental, destacando a importância das características desses habitats nos processos ecológicos dentro dos riachos.

Use of functional traits to assess changes in stream fish assemblages across a habitat gradient

Functional traits are important for understanding the links between species occurrence and environmental conditions. Identifying these links makes it possible to predict changes in species composition within communities under specific environmental conditions. We used functional traits related to habitat use and trophic ecology in order to assess the changes in fish community composition between streams with varying habitat structure. The relationship between the species traits and habitat characteristics was analyzed using an RLQ ordination analysis. Although species were widely distributed in habitats with different structures, physical conditions did favor some species based on their functional characteristics. Eight functional traits were found to be associated with stream habitat structure, allowing us to identify traits that may predict the susceptibility of fish species to physical habitat degradation.(AU)

Os atributos funcionais são importantes para entender a ligação entre ocorrência das espécies e condições ambientais, permitindo predizer sobre as mudanças na composição de espécies em comunidades submetidas a condições ambientais específicas. Utilizamos atributos funcionais relacionados com o uso de habitat e ecologia trófica para avaliar as mudanças na composição de espécies de peixes em riachos com diferenças na estrutura física. O relacionamento entre os atributos das espécies e as variáveis ambientais foi avaliado por meio da análise de ordenação RLQ. Embora algumas espécies tenham sido amplamente distribuídas em hábitats com diferentes características, outras foram restritas por essas condições e este relacionamento está associado com as características morfológicas. Oito atributos funcionais foram capazes de detectar as variações na estrutura física do hábitat em riachos, permitindo a identificação de atributos que podem predizer a suscetibilidade das espécies de peixes para a degradação física do hábitat.(AU)

Environmental constraints structuring fish assemblages in riffles: evidences from a tropical stream

Riffles are unique habitats regarding to assemblage structure. However, understanding how these assemblages respond to environmental variations in small spatial extents, as within a stream, is a challenge. We assess whether the quantitative structure and the trophic composition of fish assemblages vary predictably among stream riffles. We predict that the variation of environmental conditions will explain species abundance and trophic composition, with the latter presenting higher predictive power, since species would be filtered according to their traits (e.g. diet). Moreover, we expect that the low among-riffle dispersal limitation within a stream and the strong habitat filtering would result in lower importance of spatial variables in the structure of riffle fish assemblages. We tested these predictions by studying 18 riffles of a stream in the Central Brazil. Environmental variables, but not spatial ones, were the most important in explaining the variation in assemblages structure. Environmental variables explained a greater portion of the trophic structure variation (R2=0.62) than of abundance (R2=0.37), indicating that the variation on the trophic traits at community level are more predictable. These results also indicate that these assemblages are subject to environmental control, highlighting the importance of riffle characteristics in driving ecological processes within streams.(AU)

Corredeiras são habitats singulares no que se refere à estrutura das suas assembleias. Entretanto, a compreensão sobre como essas assembleias respondem às variações ambientais em pequenas extensões espaciais, como dentro de um riacho, ainda é um desafio. Avaliamos se a estrutura quantitativa das assembleias de peixes, assim como a sua composição trófica variam previsivelmente entre corredeiras de riachos. Predizemos que a variação nas condições ambientais explicará a abundância das espécies, assim como a sua composição trófica, entretanto, com uma maior proporção da variação explicada para a segunda, já que as espécies seriam filtradas de acordo com seus atributos (e.g. dieta). Além disso, esperamos que a pequena limitação para a dispersão entre as corredeiras de um mesmo riacho, associada à forte filtragem ambiental, resultaria em uma menor importância de variáveis espaciais na estruturação das assembleias de corredeiras. Para testar essas predições, estudamos 18 corredeiras de um rio do Brasil Central. As variáveis ambientais, e não as espaciais, foram mais importantes para explicar a variação na estrutura das assembleias. As variáveis ambientais explicaram uma maior proporção da variação da composição trófica (R2=0,62), em comparação com a abundância (R2=0,37), indicando maior previsibilidade na variação dos atributos relacionados a dieta em nível de comunidade. Esses resultados também indicam que essas assembleias são sujeitas a forte controle ambiental, destacando a importância das características desses habitats nos processos ecológicos dentro dos riachos.(AU)

Fish complementarity is associated to forests in Amazonian streams

The functional structure of communities is commonly measured by the variability in functional traits, which may demonstrate complementarity or redundancy patterns. In this study, we tested the influence of environmental variables on the functional structure of fish assemblages in Amazonian streams within a deforestation gradient. We calculated six ecomorphological traits related to habitat use from each fish species, and used them to calculate the net relatedness index (NRI) and the nearest taxon index (NTI). The set of species that used the habitat differently (complementary or overdispersed assemblages) occurred in sites with a greater proportion of forests. The set of species that used the habitat in a similar way (redundant or clustered assemblages) occurred in sites with a greater proportion of grasses in the stream banks. Therefore, the deforestation of entire watersheds, which has occurred in many Amazonian regions, may be a central factor for the functional homogenization of fish fauna.

A estrutura funcional das comunidades é comumente medida através da variabilidade nos traços funcionais, que pode demonstrar padrões de complementaridade ou redundância. Testamos a influência de variáveis ambientais na estrutura funcional de peixes de riachos Amazônicos ao longo do gradiente de desmatamento. Para cada espécie, calculamos seis traços ecomorfológicos relacionados ao uso do hábitat e usamos esses traços para calcular o índice de proximidade de táxon (NRI) e o índice do táxon mais próximo (NTI). Os conjuntos de espécies que usam o hábitat de modo distinto (comunidades complementares) ocorreram em trechos de microbacias com maior proporção de florestas, e os conjuntos de espécies que utilizam o hábitat de forma similar (comunidades redundantes) ocorreram em trechos com maior proporção de gramíneas nas margens. Portanto, o desmatamento de microbacias inteiras, como vem acontecendo em muitas regiões Amazônicas, pode ser o fator principal para a homogeneização funcional da ictiofauna.

Fish complementarity is associated to forests in Amazonian streams

The functional structure of communities is commonly measured by the variability in functional traits, which may demonstrate complementarity or redundancy patterns. In this study, we tested the influence of environmental variables on the functional structure of fish assemblages in Amazonian streams within a deforestation gradient. We calculated six ecomorphological traits related to habitat use from each fish species, and used them to calculate the net relatedness index (NRI) and the nearest taxon index (NTI). The set of species that used the habitat differently (complementary or overdispersed assemblages) occurred in sites with a greater proportion of forests. The set of species that used the habitat in a similar way (redundant or clustered assemblages) occurred in sites with a greater proportion of grasses in the stream banks. Therefore, the deforestation of entire watersheds, which has occurred in many Amazonian regions, may be a central factor for the functional homogenization of fish fauna.(AU)

A estrutura funcional das comunidades é comumente medida através da variabilidade nos traços funcionais, que pode demonstrar padrões de complementaridade ou redundância. Testamos a influência de variáveis ambientais na estrutura funcional de peixes de riachos Amazônicos ao longo do gradiente de desmatamento. Para cada espécie, calculamos seis traços ecomorfológicos relacionados ao uso do hábitat e usamos esses traços para calcular o índice de proximidade de táxon (NRI) e o índice do táxon mais próximo (NTI). Os conjuntos de espécies que usam o hábitat de modo distinto (comunidades complementares) ocorreram em trechos de microbacias com maior proporção de florestas, e os conjuntos de espécies que utilizam o hábitat de forma similar (comunidades redundantes) ocorreram em trechos com maior proporção de gramíneas nas margens. Portanto, o desmatamento de microbacias inteiras, como vem acontecendo em muitas regiões Amazônicas, pode ser o fator principal para a homogeneização funcional da ictiofauna.(AU)

Functional differentiation between fish assemblages from forested and deforested streams

We tested the hypothesis that streams in deforested areas shelter different fish communities to nearby forested areas, and that these disparities are due to environmental parameters that limit or benefit different species according to their functional traits. We compared the community composition of three south east Brazilian streams flanked by riparian forest with three nearby streams in deforested areas. The following functional traits were considered: diet, habitat use, water flow preference, size, and hypoxia tolerance. Differentiation between forested and deforested streams corresponded with the different contributions of three functional groups. Species reported in the literature to be hypoxia tolerant, and exhibiting a variable combination of the other traits prevailed in deforested streams, although we did not find substantial differences in oxygen levels between forested and deforested streams. In forested streams, benthic species associated with a high water flow and an insectivorous diet were dominant. Changes in streams induced by deforestation which are associated with habitat availability, food resources, and physicochemical conditions appear to restrict the occurrence of specialized species and instead benefit tolerant generalists.

A hipótese de que as alterações ambientais causadas pelo desmatamento nos riachos podem restringir a ocorrência de espécies a partir de suas características funcionais foi testada. Comparamos a composição das comunidades de três riachos do sudeste do Brasil providos de floresta riparia nas suas margens com três riachos da mesma região com zona ripária desmatada. Os seguintes atributos funcionais foram considerados: dieta, uso de hábitat, preferência por fluxo, tamanho e tolerância à hipóxia. A diferenciação dos riachos, em especial entre os riachos florestados e desmatados, foi maior do que o esperado ao acaso e correspondeu à contribuição diferencial de três grupos funcionais. As espécies indicadas na literatura como sendo tolerantes à hipóxia e que apresentaram combinação variável das outras características foram mais abundantes nos riachos desmatados, embora não tenhamos observado diferenças substanciais nos níveis de oxigênio dissolvido entre os riachos florestados e desmatados. Nos riachos florestados predominaram espécies de hábitos especializados, bentônicas, associadas com alta velocidade de água e dieta insetívora. As alterações nos riachos provocadas pelo desmatamento relacionadas com a disponibilidade de hábitat, recursos alimentares e condições físico-químicas restringem a ocorrência de grupos de espécies especializadas e beneficiam espécies tolerantes e generalistas.