Impacts of an urban flood control infrastructure on the limnology and ichthyofauna of a basaltic Cuesta stream (southeast Brazil).

Strategies for flood control associated to extreme precipitation events in urban areas are urgent, in order to prevent not only material damages but also to avoid human losses. The construction of flood contention reservoirs ("piscinões") has become a common engineering intervention in urban and peri-urban areas. However, there is a lack of studies focused on the evaluation of environmental impacts of this type of construction. This study intended to verify the ecological effects of a retention reservoir built directly on the course of the Cascata stream, Botucatu (SP). Three sampling sites were selected, located upstream the reservoir, in the reservoir and downstream. Samplings were carried out in July (winter - dry) and November (late spring - rainy) 2020. In situ measurements were obtained through a multiparameter probe (temperature, pH, electrical conductivity, dissolved oxygen, total dissolved solids, and oxidation-reduction potential) and water samples were collected for laboratory determinations (nitrogen, total phosphorus, thermotolerant coliforms, and chlorophyll-a). For fish sampling, manual trawls, sieves and hand nets were used, with a sampling effort of 10 throws per artefact and site. Despite the small distance between the sampling points (~1,300 m) considerable changes in the limnological conditions and fish community structure were observed. The studied environment is originally a small river surrounded by riparian forest, but this characteristic was abruptly changed in the reservoir stretch, with the direct exposition of a much larger water surface to intense solar radiation and atmosphere exchanges. Consequently, as evidenced by the PCA analysis, there was a considerable (stream-reservoir increase) of temperature, dissolved oxygen and chlorophyll. However, this spatial trend was partially disturbed by an accidental sewage-pipe rupture (posteriorly fixed) adjacent to the first sampling point, due to a previous event of extreme precipitation, which resulted in increased values of nutrients, chlorophyll, conductivity and thermotolerant coliforms. Eleven fish species were collected (two non-native), belonging to seven families and five orders. The upstream reference point (despite not be pristine), was characterized by the predominance of native species, while the reservoir condition favored the development of large populations of the non-native species. Despite the urgency of effective actions to prevent floods in urban areas, construction of contention reservoirs directly on stream courses should be avoided, due to their negative ecological impacts.

Potential impact of small hydroelectric power plants on river biota: a case study on macroinvertebrates associated to basaltic knickzones / Potencial impacto de pequenas centrais hidreléticas sobre a biota aquática: um estudo de caso sobre macroinvertebrados associados a pedrais basálticos

Abstract Small hydroelectric power plants (SHP) have been considered as an alternative for the generation of electricity with reduced environmental impacts. Nevertheless, no studies have addressed changes in a particular kind of river macrohabitat commonly affected by SHPs, the knickzones. This study aimed to assess the impact of a SHP construction on the aquatic macroinvertebrate fauna associated with two basaltic knickzones located in Sapucaí-Mirim River, Southeast Brazil. The first, considered as a functional knickzone, follows the natural dynamics of the river flow and preserves the original rock substrate. The second, considered as non-functional knickzone, was permanently flooded after the SHP construction and the consolidated rock substrate was changed by fine sediment. Sampling was carried out in two seasonal periods and the data were analysed through multivariate analysis. It was observed differences in composition and structure of the macroinvertebrates community between the knickzones and periods. The functional knickzone exhibited a much higher richness, 72 taxa compared to 44 in the non-functional, as well as a large number of exclusive taxa (38, being only nine exclusive to the non-functional). Diversity, equitability and density mean values were also higher in the functional knickzone. The limnological parameters varied significantly between dry and rainy seasons but not between the distinct knickzones. This kind of macrohabitats and its potential role for the rivers biodiversity is practically unknown. In the scenery of fast SHP expansion, further studies and protection measures are necessary.

Resumo Atualmente, a instalação de pequenas centrais hidrelétricas (PCHs) tem sido a alternativa mais visada quando a questão é suprir a demanda energética, considerando-se os menores impactos ambientais possíveis. Contudo, são escassos os trabalhos que avaliam as alterações causadas por esses empreendimentos, principalmente no que se diz respeito a um tipo de macro-habitat de rios, os pedrais. Assim, este estudo teve como objetivo avaliar o impacto da construção de uma PCH na fauna de macroinvertebrados aquáticos associada a dois pedrais basálticos, localizados no rio Sapucaí-Mirim, no Sudeste do Brasil. O primeiro, considerado como um pedral funcional, segue a dinâmica natural do fluxo do rio e possui o substrato rochoso original. O segundo, considerado como pedral não funcional, foi permanentemente inundado após a construção da PCH e o substrato consolidado foi alterado por sedimentos finos. A amostragem foi realizada em dois períodos sazonais e os dados foram analisados através de análise multivariada. Foram observadas diferenças na composição e estrutura da comunidade de macroinvertebrados entre os pedrais e períodos. O pedral funcional apresentou uma riqueza muito maior, 72 táxons em comparação com 44 no não funcional, bem como um grande número de táxons exclusivos (38, sendo apenas nove exclusivos do não-funcional). Os valores médios da diversidade, equitabilidade e densidade também foram maiores no pedral funcional. Os parâmetros limnológicos variaram significativamente entre as estações seca e chuvosa, mas não entre os diferentes pedrais. Este tipo de macro-habitat e seu potencial papel para a biodiversidade dos rios são praticamente desconhecidos. Assim, mais estudos e medidas de proteção são necessários, principalmente diante do atual cenário de rápida expansão das PCHs.

Potential impact of small hydroelectric power plants on river biota: a case study on macroinvertebrates associated to basaltic knickzones.

Small hydroelectric power plants (SHP) have been considered as an alternative for the generation of electricity with reduced environmental impacts. Nevertheless, no studies have addressed changes in a particular kind of river macrohabitat commonly affected by SHPs, the knickzones. This study aimed to assess the impact of a SHP construction on the aquatic macroinvertebrate fauna associated with two basaltic knickzones located in Sapucaí-Mirim River, Southeast Brazil. The first, considered as a functional knickzone, follows the natural dynamics of the river flow and preserves the original rock substrate. The second, considered as non-functional knickzone, was permanently flooded after the SHP construction and the consolidated rock substrate was changed by fine sediment. Sampling was carried out in two seasonal periods and the data were analysed through multivariate analysis. It was observed differences in composition and structure of the macroinvertebrates community between the knickzones and periods. The functional knickzone exhibited a much higher richness, 72 taxa compared to 44 in the non-functional, as well as a large number of exclusive taxa (38, being only nine exclusive to the non-functional). Diversity, equitability and density mean values were also higher in the functional knickzone. The limnological parameters varied significantly between dry and rainy seasons but not between the distinct knickzones. This kind of macrohabitats and its potential role for the rivers biodiversity is practically unknown. In the scenery of fast SHP expansion, further studies and protection measures are necessary.

More than two decades after the introduction of Limnoperna fortunei (Dunker 1857) in La Plata Basin / Duas décadas após a chegada de Limnoperna fortunei (Dunker 1857) na Bacia do Prata

Abstract The golden mussel, Limnoperna fortunei, is an Asian freshwater bivalve introduced in South America in the beginning of the 1990's, probably through ballast water releases in La Plata River estuary. It dispersed north through Paraná, Uruguay and Paraguay Rivers. The study evaluated the macroscale (18° to 34° S; 45° to 60° W) distribution of L. fortunei (larval stages) in the main rivers and reservoirs of La Plata Basin. Samplings were performed through 68 µm vertical plankton net hauls. Limnological variables were simultaneously determined. Larvae abundance correlated significantly with oxygen (positively) in summer, with temperature (positively) in winter and with total phosphorus and total nitrogen (both negatively) in winter. We expected densities to decrease towards north (latitudinal gradient) and increase in lentic conditions (reservoirs). Despite maximum density was found near the introduction point (La Plata River) similar value was also observed 2,000 km north (Paraguay River). The first hypothesis was refuted. The second hypothesis was partially accepted. Abundances were consistently higher in summer. Higher trophic conditions and fast flow seem to inhibit population growth. Food resources (chlorophyll a) locally influenced temporal variation. Limnoperna fortunei is widely distributed in La Plata basin, reaching high larval densities superior to 10,000 ind. m-3, in all major sub-basins. The species exhibits a high intrinsic dispersal ability (free planktonic larvae), wide tolerance to environmental factors and dispersion is potentialized by natural dispersion processes (e.g. fauna displacement) and human facilitation (e.g. commercial navigation).

Resumo O mexilhão dourado, Limnoperna fortunei, é um bivalve de água doce originário da Ásia e introduzido na América do Sul no início de 1990, provavelmente através da água de lastro liberada no estuário do rio La Plata. Dispersando-se para o norte através dos rios Paraná, Uruguai e Paraguai. Esse estudo avaliou a distribuição em macroescala (18° a 34° S; 45° a 60° W) de L. fortunei (estágios larvais) nos principais rios e reservatórios da bacia La Plata. Amostragens foram realizadas através de arrastos verticais com rede planctônica de 68 µm. Variáveis limnológicas foram simultaneamente determinadas. A abundância larval correlacionou-se significativamente com oxigênio (positivamente) no verão, com a temperatura (positivamente) no inverno e com fósforo total e nitrogênio total (ambos negativamente) no inverno. Esperávamos um decréscimo da densidade em direção ao norte (gradiente latitudinal) e aumento em condições lênticas (reservatórios). Apesar de a densidade máxima ter sido encontrada próximo do ponto de introdução (La Plata River) valores similares também foram observados 2.000 km ao norte (rio Paraguai). A primeira hipótese foi refutada. A segunda hipótese foi parcialmente aceita. Abundâncias foram consistentemente maiores no verão. Condições eutróficas e fluxo rápido parecem inibir o crescimento populacional. Recurso alimentar (clorofila a) local influenciou a variação temporal. Limnoperna fortunei está amplamente distribuído na bacia de La Plata, alcançando densidades larvais superiores a 10.000 ind. m-3 em todas as principais sub bacias. A espécie possui alta capacidade de dispersão intrínseca (larva planctônica livre), ampla tolerância aos fatores ambientais e os processos de dispersão são potencializados por processos naturais (e.g. deslocamento de fauna) e facilitação humana (e.g. navegação comercial).

A contribution for the limnological knowledge of basaltic knickzones / Uma contribuição para o conhecimento limnológico dos pedrais basálticos

Abstract The knickzones are defined as locally steep riverbed segments, such as a convex reach in a concave-up longitudinal profile. They are worldwide distributed and geologically well studied, but despite their distinctiveness as a particular kind of macrohabitat there is a notorious lack of ecological knowledge. In this context, this research proposal aims to provide a physical description, in terms of kind of habitats, and a limnological characterization of a basaltic knickzone. Information is based on a case study carried out in the Sapucaí-Mirim River, Southeast Brazil. Samplings were performed in three different habitats well represented in the knickzone (runs, riffles and pools) during rainy and dry conditions. A clear discrimination in terms of habitat type and seasonality was demonstrated through a principal component analysis. Pools exhibited higher amplitude of variation for most limnological parameters when compared to runs and riffles, probably due to a great influence of the internal metabolism (photosynthetic production and community respiration). Despite of their geological ancient formation and the little understanding of their ecological role, the knickzones are in imminent threat in several regions of the world by hydropower dams implementation. The lack of ecological information on knickzones is probably due to inherent access difficulties and how to compare the distinct kinds of habitats. Thereby, further studies should be encouraged.

Resumo Os pedrais são definidos como segmentos de rio com leito localmente íngreme, tais como um alcance convexo em um perfil longitudinal côncavo. Eles são mundialmente distribuídos e geologicamente bem estudados, mas apesar de sua distinção como um tipo particular de macrohabitat há uma notória falta de conhecimento ecológico. Neste contexto, a proposta desta pesquisa é fornecer uma descrição física, em termos de tipo de habitats, e uma caracterização limnológica de um pedral basáltico. A informação é baseada em um estudo de caso realizado no rio Sapucaí-Mirim, no Sudeste do Brasil. As amostragens foram realizadas em três diferentes habitats bem representados na zona de pedral (rápidos, corredeiras e poças) durante as condições chuvosa e seca. Uma clara discriminação em termos de tipo de habitat e sazonalidade foi demonstrada através de uma análise de componentes principais. As poças apresentaram maior amplitude de variação para a maioria dos parâmetros limnológicos quando comparadas aos rápidos e corredeiras, provavelmente devido a grande influência do metabolismo interno (produção fotossintética e respiração das comunidades). Apesar de sua formação geológica antiga e da pouca compreensão de seu papel ecológico, os pedrais estão em ameaça iminente em várias regiões do mundo pela implementação de barragens hidrelétricas. A falta de informações ecológicas sobre os pedrais é provavelmente devido às dificuldades inerentes de acesso e como comparar os tipos distintos de habitats. Assim, devem ser encorajados novos estudos.

More than two decades after the introduction of Limnoperna fortunei (Dunker 1857) in La Plata Basin.

The golden mussel, Limnoperna fortunei, is an Asian freshwater bivalve introduced in South America in the beginning of the 1990's, probably through ballast water releases in La Plata River estuary. It dispersed north through Paraná, Uruguay and Paraguay Rivers. The study evaluated the macroscale (18° to 34° S; 45° to 60° W) distribution of L. fortunei (larval stages) in the main rivers and reservoirs of La Plata Basin. Samplings were performed through 68 µm vertical plankton net hauls. Limnological variables were simultaneously determined. Larvae abundance correlated significantly with oxygen (positively) in summer, with temperature (positively) in winter and with total phosphorus and total nitrogen (both negatively) in winter. We expected densities to decrease towards north (latitudinal gradient) and increase in lentic conditions (reservoirs). Despite maximum density was found near the introduction point (La Plata River) similar value was also observed 2,000 km north (Paraguay River). The first hypothesis was refuted. The second hypothesis was partially accepted. Abundances were consistently higher in summer. Higher trophic conditions and fast flow seem to inhibit population growth. Food resources (chlorophyll a) locally influenced temporal variation. Limnoperna fortunei is widely distributed in La Plata basin, reaching high larval densities superior to 10,000 ind. m-3, in all major sub-basins. The species exhibits a high intrinsic dispersal ability (free planktonic larvae), wide tolerance to environmental factors and dispersion is potentialized by natural dispersion processes (e.g. fauna displacement) and human facilitation (e.g. commercial navigation).

A contribution for the limnological knowledge of basaltic knickzones.

The knickzones are defined as locally steep riverbed segments, such as a convex reach in a concave-up longitudinal profile. They are worldwide distributed and geologically well studied, but despite their distinctiveness as a particular kind of macrohabitat there is a notorious lack of ecological knowledge. In this context, this research proposal aims to provide a physical description, in terms of kind of habitats, and a limnological characterization of a basaltic knickzone. Information is based on a case study carried out in the Sapucaí-Mirim River, Southeast Brazil. Samplings were performed in three different habitats well represented in the knickzone (runs, riffles and pools) during rainy and dry conditions. A clear discrimination in terms of habitat type and seasonality was demonstrated through a principal component analysis. Pools exhibited higher amplitude of variation for most limnological parameters when compared to runs and riffles, probably due to a great influence of the internal metabolism (photosynthetic production and community respiration). Despite of their geological ancient formation and the little understanding of their ecological role, the knickzones are in imminent threat in several regions of the world by hydropower dams implementation. The lack of ecological information on knickzones is probably due to inherent access difficulties and how to compare the distinct kinds of habitats. Thereby, further studies should be encouraged.

Habitat architecture influencing microcrustaceans composition: a case study on freshwater Cladocera (Crustacea Branchiopoda).

Environmental complexity is considered a key factor for diversity enhancement in aquatic ecosystems. Macrophyte stands are a major contributor for this complexity due to their differential architectures. Nevertheless, the influence of distinct aquatic habitat architectures (with different types of macrophytes or without them) on microcrustaceans' taxa composition, usually found in macrophyte colonized water bodies, is underexplored in limnological studies. The main objective of this study was to analyze this influence by comparing the Cladocera composition among four habitat architectures: (1) fluctuant macrophytes, (2) rooted emergent macrophytes, (3) submerged macrophytes and (4) the limnetic zone of oxbow lakes associated to a large subtropical reservoir. Wide compositional variation was observed. Fluctuant macrophytes exhibited the richest Cladocera assemblage, dominated by Chydoridae. Submerged and rooted emergent macrophytes had the most similar assemblages between them. The most distinctive fauna was found in the limnetic zone, dominated by Bosminidae. Probable differences in resource availability in each sampled habitat architecture are considered as the driving factor for the Cladocera composition variation. We concluded that for a complete inventory of a given local fauna, it is imperative to take into account the aquatic habitat architecture, including macrophyte stands, in the data sampling design.

Habitat architecture influencing microcrustaceans composition: a case study on freshwater Cladocera (Crustacea Branchiopoda) / Arquitetura do habitat influenciando a composição taxonômica de microcrustáceos: um estudo de caso sobre Cladocera de águas continentais (Crustacea Branchiopoda)

Abstract Environmental complexity is considered a key factor for diversity enhancement in aquatic ecosystems. Macrophyte stands are a major contributor for this complexity due to their differential architectures. Nevertheless, the influence of distinct aquatic habitat architectures (with different types of macrophytes or without them) on microcrustaceans’ taxa composition, usually found in macrophyte colonized water bodies, is underexplored in limnological studies. The main objective of this study was to analyze this influence by comparing the Cladocera composition among four habitat architectures: (1) fluctuant macrophytes, (2) rooted emergent macrophytes, (3) submerged macrophytes and (4) the limnetic zone of oxbow lakes associated to a large subtropical reservoir. Wide compositional variation was observed. Fluctuant macrophytes exhibited the richest Cladocera assemblage, dominated by Chydoridae. Submerged and rooted emergent macrophytes had the most similar assemblages between them. The most distinctive fauna was found in the limnetic zone, dominated by Bosminidae. Probable differences in resource availability in each sampled habitat architecture are considered as the driving factor for the Cladocera composition variation. We concluded that for a complete inventory of a given local fauna, it is imperative to take into account the aquatic habitat architecture, including macrophyte stands, in the data sampling design.

Resumo A complexidade ambiental é considerada um fator chave para o aumento na diversidade de ambientes aquáticos. A presença de bancos de macrófitas é um dos principais contribuintes para tal complexidade devido às suas arquiteturas diferenciadas. Entretanto, a influência de diferentes arquiteturas de habitat (com diferentes macrófitas ou sem elas) sobre a composição taxonômica de microcrustáceos, comumente encontrados em ambientes colonizados por macrófitas, é pouco explorada em estudos limnológicos. O objetivo desse estudo foi avaliar esta influência através da comparação da composição das associações de Cladocera entre quatro arquiteturas de habitat: (1) macrófitas flutuantes, (2) macrófitas enraizadas emersas, (3) macrófitas submersas e (4) a zona limnética em lagoas laterais associadas a um grande reservatório subtropical. Ampla variação composicional foi observada. Macrófitas flutuantes apresentaram as mais ricas assembléias de Cladocera, dominadas por Chydoridae. Macrófitas submersas e emersas enraizadas apresentaram as associações mais similares. A fauna mais distinta foi a da zona limnética, dominada por Bosminidae. Prováveis diferenças na disponibilidade de recursos entre as arquiteturas de habitat amostradas foram consideradas o fator mais relevante levando à variação composicional dos microcrustáceos. Concluímos que para um inventário completo de uma determinada fauna local é imperativo que seja considerada a arquitetura dos habitats aquáticos, incluindo os bancos de macrófitas, no desenho amostral.

Impact assessment of the introduction of Cichla kelberi in a large Neotropical reservoir and its lateral lagoons (Upper Paraná River Basin, Brazil).

This study aimed to understand how the introduction of Cichla kelberi in Rosana Reservoir (Paranapanema River) affected the native ichthyofauna. Data on the structure of the small fish fauna assemblage were obtained before and after the introduction of this carnivorous species. Samplings were carried out in February and September of 2004, previously to the register of Cichla kelberi in the reservoir, and after its introduction, November of 2004, January, March, May and August of 2005, February and June of 2006, February and July of 2007, February and October of 2008 and February of 2009. A total of 4,693 fish, belonging to 43 different species was sampled between 2004 and 2009. The order Characiformes was the most abundant, followed by Perciformes and Siluriformes. Comparative analyses, before and after the introduction, could not demonstrate significant changes in composition, richness, abundance, biomass, mean length and diversity of fish. Aquatic insects were the main feeding item of C. kelberi, followed by tetragonopterinae fish. Cannibalism was recorded during the whole study period. The results showed that Cichla cannot deeply affect the ichthyofauna assemblages of a large Neotropical reservoir, at least in a short or medium term period after its introduction. The results also allowed concluding that the introduction of C. kelberi in the reservoir is in the phase 3. In this phase, the specie can survive and reproduce in the new environment; however it is not totally established and disseminated. The reasons for the fact that Cichla is still not dominant in Rosana Reservoir could be related to feeding competition, high rate of cannibalism and the presence of large amount of aquatic macrophytes (refuge zones). In spite of the results, the continuous monitoring of the role of non-native species on the local fish fauna is absolutely necessary because the impacts caused by colonization of this undesirable species can be magnified by complex processes, usually correlated with other environmental disturb, especially the negative effects of damming.

Impact assessment of the introduction of Cichla kelberi in a large Neotropical reservoir and its lateral lagoons (Upper Paraná River Basin, Brazil) / Avaliação do impacto da introdução da Cichla kelberi em um reservatório Neotropical de grande porte e suas lagoas laterais (Bacia do Alto Paraná, Brasil)

Abstract This study aimed to understand how the introduction of Cichla kelberi in Rosana Reservoir (Paranapanema River) affected the native ichthyofauna. Data on the structure of the small fish fauna assemblage were obtained before and after the introduction of this carnivorous species. Samplings were carried out in February and September of 2004, previously to the register of Cichla kelberi in the reservoir, and after its introduction, November of 2004, January, March, May and August of 2005, February and June of 2006, February and July of 2007, February and October of 2008 and February of 2009. A total of 4,693 fish, belonging to 43 different species was sampled between 2004 and 2009. The order Characiformes was the most abundant, followed by Perciformes and Siluriformes. Comparative analyses, before and after the introduction, could not demonstrate significant changes in composition, richness, abundance, biomass, mean length and diversity of fish. Aquatic insects were the main feeding item of C. kelberi, followed by tetragonopterinae fish. Cannibalism was recorded during the whole study period. The results showed that Cichla cannot deeply affect the ichthyofauna assemblages of a large Neotropical reservoir, at least in a short or medium term period after its introduction. The results also allowed concluding that the introduction of C. kelberi in the reservoir is in the phase 3. In this phase, the specie can survive and reproduce in the new environment; however it is not totally established and disseminated. The reasons for the fact that Cichla is still not dominant in Rosana Reservoir could be related to feeding competition, high rate of cannibalism and the presence of large amount of aquatic macrophytes (refuge zones). In spite of the results, the continuous monitoring of the role of non-native species on the local fish fauna is absolutely necessary because the impacts caused by colonization of this undesirable species can be magnified by complex processes, usually correlated with other environmental disturb, especially the negative effects of damming.

Resumo O objetivo deste estudo foi entender como a introdução da Cichla kelberi no reservatório de Rosana (rio Paranapanema) afeta as assembléias de peixes. Dados da estrutura da ictiofauna de pequeno porte foram obtidos antes e após a introdução dessa espécie carnívora. As coletas foram realizadas em fevereiro e setembro de 2004, quando Cichla kelberi, ainda não havia sido registrado no reservatório, e após sua presença, em novembro de 2004, janeiro, março, maio e agosto de 2005, fevereiro e junho de 2006, fevereiro e julho de 2007, fevereiro e outubro de 2008 e fevereiro de 2009. Um total de 4693 peixes, pertencentes a 43 espécies foi amostrado entre 2004 e 2009. A Ordem Characiformes foi a mais abundante, seguida por Perciformes e Siluriformes. Análises comparativas, antes e depois da introdução, não demonstraram mudanças significativas na composição, riqueza, abundância, biomassa, comprimento médio e diversidade dos peixes. Insetos aquáticos constituíram no principal item da alimentação de Cichla kelberi, seguido por peixes tetragonopterídeos. Canibalismo foi registrado durante todo o período de estudo. Os resultados mostraram que Cichla não afeta substancialmente a ictiofauna dos reservatórios neotropicais, pelo menos no curto e médio prazo após sua introdução. Os resultados também permitiram concluir que a introdução de Cichla kelberi se encontra na fase 3. Nessa fase, a espécie pode sobreviver e reproduzir no novo ambiente, contudo ela não está totalmente estabelecida e disseminada. As razões que explicam a ausência de dominância de Cichla no reservatório de Rosana podem estar relacionadas à competição alimentar, a alta taxa de canibalismo e grande quantidade de macrófitas aquáticas (zonas de refúgio). Apesar dos resultados, o monitoramento contínuo do papel das espécies não nativas sobre a ictiofauna local é de extrema importância, pelo fato de que os impactos causados por essas espécies podem ser amplificados, geralmente correlacionados com outros distúrbios ambientais, principalmente efeitos negativos do barramento.

Differences in ichthyofauna feeding habits among lateral lagoons and the river channel in a large reservoir.

In this study, we investigated differences in feeding habits of small-sized ichthyofauna among lateral lagoons and the river channel in a large reservoir. The study was performed in four lagoons and in one sampling site of the main channel in Rosana Reservoir, Paranapanema River, Brazil. The samples were taken in September and November of 2004 and in January, March, May, and August of 2005. Fish were sampled with a 7.5 m2 hand net. Five manual throws were made toward aquatic macrophytes stands. The sampling design favored the collection of small-sized fish fauna (juveniles/small-sized species). The stomach contents of 42 species were analyzed. A total of 183 different items were consumed by fish. These items were grouped in 11 food categories, which were used to classify fish into seven trophic guilds. Aquatic insects were consumed by 32 species and were the predominant feeding item. In the river, the most consumed items were aquatic insects, cladocerans, and phytoplankton, whereas in the lagoons aquatic insects, copepods, and cladocerans were the main items. By comparing each trophic guild, the number of insectivores, algivores, and zooplanktivores species was higher in the lagoons than in the river, and the opposite was found only for omnivore fish. Low niche width in all sites indicates high trophic specialization and low niche overlap between pairs of species. Fish assemblage in the lateral lagoons presents feeding habits distinct from those of the river species, indicating that the coexistence and high abundance of small-sized fish in the sampling sites are explained by their high feeding adaptability, which includes a tendency toward dietary specialization, low feeding overlap, and resource partitioning, along with different temporal resource uses.

Effect of the route of administration on the mucosal and systemic immune responses to Lawsonia intracellularis vaccine in pigs.

In an on-farm study, 40 weaned piglets aged 3 weeks were vaccinated with Lawsonia intracellularis vaccine orally, IM or IP while a fourth group remained unvaccinated. All vaccinated animals showed increased serum levels of L. intracellularis-specific IgG antibodies, but significantly elevated concentrations of specific IgG, IgA and cytokines were generated in ileal mucosal secretions from the orally and IP vaccinated pigs when examined at 17 days after vaccination.

Evaluation of light-touch sensation in the buccal mucosa of leprosy patients.

OBJECTIVE: The aim of this study is to evaluate the light-touch sensation of the oral mucosa in leprosy patients. MATERIALS AND METHODS: A cross-sectional study included 228 adults, 133 being leprosy patients and 95 normal controls. To assess light-touch sensation, the five-filament standard Semmes-Weinstein kit in eight regions of the oral mucosa was used. Chi-square test was used to verify the differences in responses between the studied groups. RESULTS: Normal sensation was predominant in both groups, and diminished sensation was found also in the nonleprosy group. Normal controls showed diminished light-touch sensation in at least one point, which may be attributed to the definition of sensation normality. The chi-square test revealed no significant difference between the two groups (p = 0.43171). Severe diminished sensation was detected only in the leprosy group. CONCLUSION: It is concluded that altered light-touch sensation in the oral cavity may not be a common feature in leprosy. CLINICAL RELEVANCE: Decreased or lost sensation in skin lesions is a paramount in leprosy diagnosis; however, clinicians must be aware that this seems not to be true in the oral mucosa in leprosy cases for diagnosis purpose.

Evaluation of light-touch sensation in the buccal mucosa of leprosy patients

OBJECTIVE: The aim of this study is to evaluate the light-touch sensation of the oral mucosa in leprosy patients. MATERIALS AND METHODS: A cross-sectional study included 228 adults, 133 being leprosy patients and 95 normal controls. To assess light-touch sensation, the five-filament standard Semmes-Weinstein kit in eight regions of the oral mucosa was used. Chi-square test was used to verify the differences in responses between the studied groups. RESULTS: Normal sensation was predominant in both groups, and diminished sensation was found also in the nonleprosy group. Normal controls showed diminished light-touch sensation in at least one point, which may be attributed to the definition of sensation normality. The chi-square test revealed no significant difference between the two groups (p = 0.43171). Severe diminished sensation was detected only in the leprosy group. CONCLUSION: It is concluded that altered light-touch sensation in the oral cavity may not be a common feature in leprosy.CLINICAL RELEVANCE: Decreased or lost sensation in skin lesions is a paramount in leprosy diagnosis; however, clinicians must be aware that this seems not to be true in the oral mucosa in leprosy cases for diagnosis purpose.

Phytoplankton assemblages in lateral lagoons of a large tropical reservoir.

This study aimed to analyse the composition and ecological attributes of the phytoplankton assemblages in four lateral lagoons and in the main channel of Rosana Reservoir (Paranapanema River, SE Brazil). Fieldwork was carried out in September and November/2004 and January, March, May and August/2005. A total of 283 taxa was identified. Zygnemaphyta was the most specious group, followed by Chlorophyta and Bacillariophyta. Higher richness, abundance and biomass were observed in the lagoons when compared with the river-reservoir sampling point, especially during the rainy period. Cryptophyceae and Bacillariophyceae dominated numerically. Cryptomonas brasiliensis Castro, Bicudo and Bicudo was the main species of the phytoplankton in terms of abundance and frequency of occurrence. The dynamics of the most important taxa are discussed and the results showed that the phytoplankton assemblages are mainly influenced by meteorological factors and nutrient availability (the main driving forces). Correlation analyses indicated that the assemblage abundance was limited by nutrient (nitrogen and phosphorus). The phytoplankton abundance influenced positively the zooplankton abundance, what indicates the prevalence of bottom-up control routes in the lateral lagoons system. The results validate the hypotheses that lateral lagoons have a prominent ecological role on the phytoplankton diversity, as already previously demonstrated for fish and zooplankton. Therefore, the incorporation of the lateral lagoons in environmental programmes should be a target strategy for the conservation of the regional aquatic biota, minimising the negative impact of the dam.

Immunological responses to vaccination following experimental Lawsonia intracellularis virulent challenge in pigs.

Although a live attenuated vaccine has been used extensively to provide immunity against porcine proliferative enteropathy (PE) caused by Lawsonia intracellularis, the nature of the protective response is an area of considerable interest for the control of PE. Two trials investigated immune responses in pigs after oral and intramuscular (IM) vaccination followed by virulent L. intracellularis challenge. After an oral vaccination with 10(5.9) TCID50 organisms, significantly increased serum and mucosal secretions of IgM, IgG and higher mucosal TNF-α and TGF-ß1 were detected by day 17, together with a trend towards higher levels of IFN-γ and IL-6. Pigs vaccinated IM produced elevated serum antibody titres but mucosal immune responses were not detected. After challenge with virulent L. intracellularis, non-vaccinated control pigs had higher PE lesion scores and excreted significantly higher numbers of L. intracellularis in faeces than the vaccinated pigs. Reduced intestinal pathology and faecal L. intracellularis shedding were evident in the vaccinated groups. The results indicated that protection was associated with mucosal cytokine and specific IgG and IgA responses after vaccination and that systemic antibody responses were boosted following challenge. However in the search for an immune correlate with protection, a causal association was not evident from a kinetic analysis of immune parameters in serum, ileal pathology and faecal shedding.

Effect of organic acids and mannanoligosaccharide on excretion of Salmonella typhimurium in experimentally infected growing pigs.

The effect of organic acids and mannanoligosaccharide addition to the diet was assessed in pigs orally inoculated with Salmonella typhimurium. Forty-six growers were distributed among four treatments: Basal Diet (BD); BD+encapsulated organic acids; BD+free organic acids; BD+mannanoligosaccharide. Seroconversion was monitored, and feces and tissue samples were tested for Salmonella isolation. No treatment prevented the carrier state, but a tendency of lower fecal excretion was observed in the group treated with mannanoligosaccharide.

Phytoplankton assemblages in a reservoir cascade of a large tropical - subtropical river (SE, Brazil).

The phytoplankton assemblages from eight reservoirs of the Paranapanema River were studied during two consecutive years. Chlorophyceae and Bacillaryophyceae dominated in richness. The observed high number of taxa, 234, reflects the extensive sampling programme and evidences the necessity of considering the whole hydrograph basin to assess the biodiversity status of inland water ecosystems. The dams had a negative effect on phytoplankton richness, with higher number of taxa associate to riverine (non-regulated) stretches. The tributary rivers also exhibited high species richness, showing the importance of considering the lateral dimension, in addition to the longitudinal one, for aquatic biota inventories in large river basins/reservoirs. Richness and diversity were also positively influenced by the connectivity with lateral wetlands (macrophyte-dominated lakes) due to the periphyton influence. The phytoplankton abundance/biomass was not influenced by higher water retention time. Higher values occurred in the middle basin stretches (river-passage reservoirs) due to the increase in the trophic conditions. There was a positive correlation with phosphorus. Poorer light conditions in the cascade do not limit the phytoplankton biomass, with assemblages dominated by species tolerant to turbulent conditions and high mineral turbidity. Bacillariophyceae and Cryptophyceae dominated numerically. The first group (unicellular forms) was prominent in the large and oligotrophic upstream reservoirs. The second was highly abundant in the river-passage (low retention time), and more eutrophic, reservoirs. Cyanophyceae growth is probably controlled by advection processes (wash-out effect). The zooplankton does not control the phytoplankton biomass and the diversity of both groups is positively associated in the cascade. The structure of the phytoplankton assemblages showed to be a good indicator of the operationally distinct reservoirs of the Paranapanema cascade and also reflected the changes in the trophic conditions along the basin.

Zooplankton fluctuations in Jurumirim Reservoir (São Paulo, Brazil): a three-year study.

During three consecutive years, monthly samples of zooplankton were taken in the lacustrine (dam) zone of Jurumirim (São Paulo, Brazil). The seasonal effect on basic limnological features (thermal regime, oxygen distribution, phytoplankton biomass, etc.) was also examined. The influence of the seasonality on the fluctuation of the zooplankton composition and abundance was not clearly detected (low degree of recurrent patterns). Rotifers (32 taxa) were the most abundant organisms during almost the entire study period with some seasonal alternations in the maximum abundance peaks of the main taxa (Conochilus unicornis, Keratella americana, K. cochlearis and Hexarthra spp.), except for Polyarthra (mainly P. vulgaris). Only occasionally copepods were numerically dominant. Higher copepod abundance was positively associated to periods of increase in the water retention time. Among the Copepoda (10 taxa) the calanoids (mainly Notodiaptomus iheringi) were more abundant, especially in warmer periods. Conversely, cyclopoids had higher abundance in autumn and winter. The species Thermocyclops minutus and T. decipiens co-occurred, but the first attained higher abundance. Some evidence of co-existence strategies between both species are considered. Cladocera (17 taxa) was never numerically dominant and the main taxa (Bosmina spp., Ceriodaphnia spp. and Diaphanosoma spp.) occurred almost the whole study period and did not present a seasonal pattern of fluctuation. Diaphanosoma (mainly D. birgei) attained the highest abundance among cladocerans. Most organisms were always found at the surface, but they also occupy the whole water column, even in periods of stratified conditions and low oxygen concentration in the bottom layers. Among the main zooplanktonic taxa, only Hexarthra avoids deep layers. An exceptionally high concentration of Copepoda nauplii on the surface was influenced by low transparency, high concentration of phytoplankton at this layer and low oxygen concentration at the bottom. In periods of higher retention timevariability there was a more heterogeneous distribution of the zooplankton in the water column. The increase in the retention time seems also to favor the copepod development. Finally, some inter-decade changes are considered on the basis of zooplankton assemblage structure observations.