Intra-annual variation in rainfall and its influence of the adults Cyprideis spp (Ostracoda, Crustacea) on a eutrophic estuary (Guanabara Bay, Rio de Janeiro, Brazil) / Variação intra-annual na chuva e a sua influência nos adultos de Cyprideis spp (Ostracoda, Crustacea) em um estuário eutrofizado (Guanabara Bay, Rio de Janeiro, Brasil)

Spatial and temporal distribution of two species of adult´s ostracods (Cyprideis sp. and Cyprideis salebrosa) were studied as a function of the rainfall patterns in the Guanabara Bay, Rio de Janeiro, Brazil. Samples were taken in ten stations, along six surveys representing three periods (Dry, Early and Late Rainy) for two years. Stations were nested in four areas (Outer, Central, EPA Guapimirim and Impacted). The bottom water (temperature, salinity, dissolved oxygen and oxygen saturation) were measured in each area to characterize the influence of seasonal variations by rainfall. Cyprideis sp. and Cyprideis salebrosa showed patterns distribution to seasonality/surveys (p = 0,002 and p 0,001, respectly). The spatial distribution of Cyprideis sp was significantly different areas studied (p 0.001) indicated well defined areas and distribution in along of the surveys. However, C. salebrosa showed homogeneous distribution in along of the areas within of each survey (p 0.001). Redundancy Analysis (RDA) for the two years evidenced environment preference of the Cyprideis sp. for areas with marine conditions (high influence for channel central) and C. salebrosa for brackish water (high influence of the rivers). This observation reinforces of the existence of areas created by the seasonality of pluviometric regime, a possible dispersion of the adults ostracods and possibility the use with bioindicators.(AU)

A distribuição espacial e temporal de duas espécies de ostracodes adultos (Cyprideis sp. e Cyprideis salebrosa) foi estudada em função do padrão pluviométrico na Baía de Guanabara, Rio de Janeiro, Brasil. As amostras foram coletadas em dez estações ao longo de seis campanhas, representando três períodos (Seco, Pré e Pós Chuvoso) por dois anos. As estações foram agrupadas em quatro áreas (Externo, Central, EPA Guapimirim e Impactado). A água do fundo (temperatura, salinidade, oxigênio dissolvido e saturação de oxigênio) foi medida em cada área para caracterizar a influência das variações sazonais pela chuva. Cyprideis sp. e Cyprideis salebrosa mostrou distribuição de padrões para sazonalidade/campanhas (p = 0,002 e p 0,001, respctivamente). A distribuição espacial de Cyprideis sp. foi significativamente diferente das áreas estudadas (p 0,001) indicou áreas bem definidas e distribuição ao longo das campanhas. No entanto, C. salebrosa mostrou distribuição homogênea ao longo das áreas dentro de cada campanha (p 0,001). A Análise de Redundância (RDA) para os dois anos evidenciou a preferência ambiental dos Cyprideis sp. para áreas com condições marinhas (alta influência para o canal central) e C. salebrosa para águas salobras (alta influência dos rios). Essa observação reforça a existência de áreas criadas pela sazonalidade do regime pluviométrico, uma possível dispersão dos adultos de ostracodes e a possibilidade do uso como bioindicadores.(AU)

Intra-annual variation in rainfall and its influence of the adults Cyprideis spp (Ostracoda, Crustacea) on a eutrophic estuary (Guanabara Bay, Rio de Janeiro, Brazil).

Abstract Spatial and temporal distribution of two species of adult´s ostracods (Cyprideis sp. and Cyprideis salebrosa) were studied as a function of the rainfall patterns in the Guanabara Bay, Rio de Janeiro, Brazil. Samples were taken in ten stations, along six surveys representing three periods (Dry, Early and Late Rainy) for two years. Stations were nested in four areas (Outer, Central, EPA Guapimirim and Impacted). The bottom water (temperature, salinity, dissolved oxygen and oxygen saturation) were measured in each area to characterize the influence of seasonal variations by rainfall. Cyprideis sp. and Cyprideis salebrosa showed patterns distribution to seasonality/surveys (p = 0,002 and p 0,001, respectly). The spatial distribution of Cyprideis sp was significantly different areas studied (p 0.001) indicated well defined areas and distribution in along of the surveys. However, C. salebrosa showed homogeneous distribution in along of the areas within of each survey (p 0.001). Redundancy Analysis (RDA) for the two years evidenced environment preference of the Cyprideis sp. for areas with marine conditions (high influence for channel central) and C. salebrosa for brackish water (high influence of the rivers). This observation reinforces of the existence of areas created by the seasonality of pluviometric regime, a possible dispersion of the adults ostracods and possibility the use with bioindicators.

Resumo A distribuição espacial e temporal de duas espécies de ostracodes adultos (Cyprideis sp. e Cyprideis salebrosa) foi estudada em função do padrão pluviométrico na Baía de Guanabara, Rio de Janeiro, Brasil. As amostras foram coletadas em dez estações ao longo de seis campanhas, representando três períodos (Seco, Pré e Pós Chuvoso) por dois anos. As estações foram agrupadas em quatro áreas (Externo, Central, EPA Guapimirim e Impactado). A água do fundo (temperatura, salinidade, oxigênio dissolvido e saturação de oxigênio) foi medida em cada área para caracterizar a influência das variações sazonais pela chuva. Cyprideis sp. e Cyprideis salebrosa mostrou distribuição de padrões para sazonalidade/campanhas (p = 0,002 e p 0,001, respctivamente). A distribuição espacial de Cyprideis sp. foi significativamente diferente das áreas estudadas (p 0,001) indicou áreas bem definidas e distribuição ao longo das campanhas. No entanto, C. salebrosa mostrou distribuição homogênea ao longo das áreas dentro de cada campanha (p 0,001). A Análise de Redundância (RDA) para os dois anos evidenciou a preferência ambiental dos Cyprideis sp. para áreas com condições marinhas (alta influência para o canal central) e C. salebrosa para águas salobras (alta influência dos rios). Essa observação reforça a existência de áreas criadas pela sazonalidade do regime pluviométrico, uma possível dispersão dos adultos de ostracodes e a possibilidade do uso como bioindicadores.

Intra-annual variation in rainfall and its influence of the adults Cyprideis spp (Ostracoda, Crustacea) on a eutrophic estuary (Guanabara Bay, Rio de Janeiro, Brazil)

Abstract Spatial and temporal distribution of two species of adult´s ostracods (Cyprideis sp. and Cyprideis salebrosa) were studied as a function of the rainfall patterns in the Guanabara Bay, Rio de Janeiro, Brazil. Samples were taken in ten stations, along six surveys representing three periods (Dry, Early and Late Rainy) for two years. Stations were nested in four areas (Outer, Central, EPA Guapimirim and Impacted). The bottom water (temperature, salinity, dissolved oxygen and oxygen saturation) were measured in each area to characterize the influence of seasonal variations by rainfall. Cyprideis sp. and Cyprideis salebrosa showed patterns distribution to seasonality/surveys (p = 0,002 and p 0,001, respectly). The spatial distribution of Cyprideis sp was significantly different areas studied (p 0.001) indicated well defined areas and distribution in along of the surveys. However, C. salebrosa showed homogeneous distribution in along of the areas within of each survey (p 0.001). Redundancy Analysis (RDA) for the two years evidenced environment preference of the Cyprideis sp. for areas with marine conditions (high influence for channel central) and C. salebrosa for brackish water (high influence of the rivers). This observation reinforces of the existence of areas created by the seasonality of pluviometric regime, a possible dispersion of the adults ostracods and possibility the use with bioindicators.

Resumo A distribuição espacial e temporal de duas espécies de ostracodes adultos (Cyprideis sp. e Cyprideis salebrosa) foi estudada em função do padrão pluviométrico na Baía de Guanabara, Rio de Janeiro, Brasil. As amostras foram coletadas em dez estações ao longo de seis campanhas, representando três períodos (Seco, Pré e Pós Chuvoso) por dois anos. As estações foram agrupadas em quatro áreas (Externo, Central, EPA Guapimirim e Impactado). A água do fundo (temperatura, salinidade, oxigênio dissolvido e saturação de oxigênio) foi medida em cada área para caracterizar a influência das variações sazonais pela chuva. Cyprideis sp. e Cyprideis salebrosa mostrou distribuição de padrões para sazonalidade/campanhas (p = 0,002 e p 0,001, respctivamente). A distribuição espacial de Cyprideis sp. foi significativamente diferente das áreas estudadas (p 0,001) indicou áreas bem definidas e distribuição ao longo das campanhas. No entanto, C. salebrosa mostrou distribuição homogênea ao longo das áreas dentro de cada campanha (p 0,001). A Análise de Redundância (RDA) para os dois anos evidenciou a preferência ambiental dos Cyprideis sp. para áreas com condições marinhas (alta influência para o canal central) e C. salebrosa para águas salobras (alta influência dos rios). Essa observação reforça a existência de áreas criadas pela sazonalidade do regime pluviométrico, uma possível dispersão dos adultos de ostracodes e a possibilidade do uso como bioindicadores.

Larval and adult density of the porcellanid crab Petrolisthes armatus (Anomura: Porcellanidae) in an Amazon estuary, northern Brazil

Petrolisthes armatus (Gibbes, 1850) is a porcellanid crab with a wide geographical distribution. In the present study we analyzed variations in the abundance of P. armatus adults and larvae over an annual cycle in the Marapanim estuary of the Amazon coastal zone, in the northeastern portion of the state of Pará, Brazil. Particularly, we focused on the presence of ovigerous females and timing of larval release, with the aim of elucidating reproductive patterns in a tropical estuarine system. The mean density of P. armatus larvae (zoea I and II) correlated positively with the salinity of the shallow waters of the estuary, whereas the abundance of adults correlated with the salinity registered in water samples collected from the benthic environment. There was also a significant positive correlation between larval density (zoea I and II) and water temperature. Ovigerous females were captured throughout the study period, from August 2006 to July 2007, but were more abundant in June and less abundant during the rainy months, between February and May. Larvae were only present during the dry season and transition months (June to January), and were absent during the rainy season (February to May). Petrolisthes armatus reproduces throughout the year in the Marapanim estuary and all developmental stages of this species (zoeal stages I and II, megalopae and adults) are found in the estuary. The results indicate that the study area is an important environment for the reproduction of this decapod.

Larval and adult density of the porcellanid crab Petrolisthes armatus (Anomura: Porcellanidae) in an Amazon estuary, northern Brazil

Petrolisthes armatus (Gibbes, 1850) is a porcellanid crab with a wide geographical distribution. In the present study we analyzed variations in the abundance of P. armatus adults and larvae over an annual cycle in the Marapanim estuary of the Amazon coastal zone, in the northeastern portion of the state of Pará, Brazil. Particularly, we focused on the presence of ovigerous females and timing of larval release, with the aim of elucidating reproductive patterns in a tropical estuarine system. The mean density of P. armatus larvae (zoea I and II) correlated positively with the salinity of the shallow waters of the estuary, whereas the abundance of adults correlated with the salinity registered in water samples collected from the benthic environment. There was also a significant positive correlation between larval density (zoea I and II) and water temperature. Ovigerous females were captured throughout the study period, from August 2006 to July 2007, but were more abundant in June and less abundant during the rainy months, between February and May. Larvae were only present during the dry season and transition months (June to January), and were absent during the rainy season (February to May). Petrolisthes armatus reproduces throughout the year in the Marapanim estuary and all developmental stages of this species (zoeal stages I and II, megalopae and adults) are found in the estuary. The results indicate that the study area is an important environment for the reproduction of this decapod.

Larval and adult density of the porcellanid crab Petrolisthes armatus (Anomura: Porcellanidae) in an Amazon estuary, northern Brazil

Petrolisthes armatus (Gibbes, 1850) is a porcellanid crab with a wide geographical distribution. In the present study we analyzed variations in the abundance of P. armatus adults and larvae over an annual cycle in the Marapanim estuary of the Amazon coastal zone, in the northeastern portion of the state of Pará, Brazil. Particularly, we focused on the presence of ovigerous females and timing of larval release, with the aim of elucidating reproductive patterns in a tropical estuarine system. The mean density of P. armatus larvae (zoea I and II) correlated positively with the salinity of the shallow waters of the estuary, whereas the abundance of adults correlated with the salinity registered in water samples collected from the benthic environment. There was also a significant positive correlation between larval density (zoea I and II) and water temperature. Ovigerous females were captured throughout the study period, from August 2006 to July 2007, but were more abundant in June and less abundant during the rainy months, between February and May. Larvae were only present during the dry season and transition months (June to January), and were absent during the rainy season (February to May). Petrolisthes armatus reproduces throughout the year in the Marapanim estuary and all developmental stages of this species (zoeal stages I and II, megalopae and adults) are found in the estuary. The results indicate that the study area is an important environment for the reproduction of this decapod.

Larval and adult density of the porcellanid crab Petrolisthes armatus (Anomura: Porcellanidae) in an Amazon estuary, northern Brazil

Petrolisthes armatus (Gibbes, 1850) is a porcellanid crab with a wide geographical distribution. In the present study we analyzed variations in the abundance of P. armatus adults and larvae over an annual cycle in the Marapanim estuary of the Amazon coastal zone, in the northeastern portion of the state of Pará, Brazil. Particularly, we focused on the presence of ovigerous females and timing of larval release, with the aim of elucidating reproductive patterns in a tropical estuarine system. The mean density of P. armatus larvae (zoea I and II) correlated positively with the salinity of the shallow waters of the estuary, whereas the abundance of adults correlated with the salinity registered in water samples collected from the benthic environment. There was also a significant positive correlation between larval density (zoea I and II) and water temperature. Ovigerous females were captured throughout the study period, from August 2006 to July 2007, but were more abundant in June and less abundant during the rainy months, between February and May. Larvae were only present during the dry season and transition months (June to January), and were absent during the rainy season (February to May). Petrolisthes armatus reproduces throughout the year in the Marapanim estuary and all developmental stages of this species (zoeal stages I and II, megalopae and adults) are found in the estuary. The results indicate that the study area is an important environment for the reproduction of this decapod.

Larval and adult density of the porcellanid crab Petrolisthes armatus (Anomura: Porcellanidae) in an Amazon estuary, northern Brazil

Petrolisthes armatus (Gibbes, 1850) is a porcellanid crab with a wide geographical distribution. In the present study we analyzed variations in the abundance of P. armatus adults and larvae over an annual cycle in the Marapanim estuary of the Amazon coastal zone, in the northeastern portion of the state of Pará, Brazil. Particularly, we focused on the presence of ovigerous females and timing of larval release, with the aim of elucidating reproductive patterns in a tropical estuarine system. The mean density of P. armatus larvae (zoea I and II) correlated positively with the salinity of the shallow waters of the estuary, whereas the abundance of adults correlated with the salinity registered in water samples collected from the benthic environment. There was also a significant positive correlation between larval density (zoea I and II) and water temperature. Ovigerous females were captured throughout the study period, from August 2006 to July 2007, but were more abundant in June and less abundant during the rainy months, between February and May. Larvae were only present during the dry season and transition months (June to January), and were absent during the rainy season (February to May). Petrolisthes armatus reproduces throughout the year in the Marapanim estuary and all developmental stages of this species (zoeal stages I and II, megalopae and adults) are found in the estuary. The results indicate that the study area is an important environment for the reproduction of this decapod.

Population structure of the tanaid Sinelobus stanfordi (Richardson, 1901) (Crustacea, Tanaidacea) associated with roots of the water hyacinth Eichhornia azurea (Sw.) Kunth. (Liliiflorae, Pontederiaceae), from a coastal lagoon in Southern Brazil / Estrutura populacional do tanaídeo Sinelobus stanfordi (Richardson, 1901) (Crustacea, Tanaidacea) ocorrente em raízes do aguapé Eichhornia azurea (Sw.) Kunth. (Liliiflorae, Pontederiaceae), em uma laguna costeira do Sul do Brasil

This study aimed to investigate the population structure of Sinelobus stanfordi (Richardson, 1901) (Malacostraca, Tanaidae) in a coastal lagoon in the North coast in the Rio Grande do Sul state. The collections were performed weekly on banks of the aquatic hyacinth Eichhornia azurea (Sw.) Kunth during three months. Samples of water hyacinth were manually collected and washed on a sieve of 0.250μm mesh size. In the laboratory, the material was sorted and the tanaid lengths were measured and classified into following morphotype categories: Manca, Juveniles, Non- Reproductive Females (NRF), Preparatory Females (PREPF), Ovigerous Females (OVF) and Males. The distribution by frequency of body length classes presented a higher abundance of manca in the class of 0.75mm; juveniles in 2.19mm; non-reproductive females in 2.5mm; preparatory females in 2.7mm; ovigerous females in 2.85mm and males in 2.81mm. The average of sexual rate was 3.1:1 (females: males). It was observed the recruitment and predominance of juveniles in the eleven studied weeks, and the presence in lower proportion of PREPF, OVF and males. Based on the analyses of the population structure observed and data found in the literature, became evident the presence of juveniles, females and males during all the year, beyond a continuous reproduction activity of the species. The results have also suggested the species seems to have an opportunistic behavior, being able to colonize a high diversity of substrates.

Este trabalho buscou obter informações sobre a estrutura populacional de Sinelobus stanfordi (Richardson, 1901) (Malacostraca,Tanaidae), em intervalos semanais por um período de três meses, em uma laguna costeira do Litoral Norte do Rio Grande do Sul. As coletas foram realizadas em estande da macrófita aquática Eichhornia azurea (Sw.) Kunth. Exemplares do aguapé foram coletados manualmente e lavados sobre uma peneira de 0.250μm de abertura de malha. Em laboratório, o material foi triado e os indivíduos medidos e classificados por morfotipos: Mancas, Juvenis, Fêmeas Não-Reprodutivas (FNR), Fêmeas Preparatórias (FPREP), Fêmeas Ovadas (FOV) e Machos. A distribuição por frequências de classes de tamanho corporal demonstrou um maior número de indivíduos manca na classe de tamanho 0,75mm; juvenis, em 2,19mm; fêmeas não reprodutivas, em 2,5mm; fêmeas preparatórias, em 2,7mm; fêmeas ovadas, em 2,85mm e machos em 2,81mm. A média da proporção sexual foi de 3,1:1 (fêmeas:machos). Observou-se recrutamento e predomínio dos juvenis nas onze semanas de estudo e a presença, em menor proporção de FPREP, FOV e Machos. Com base na análise da estrutura populacional observada e dados encontrados na literatura, fica evidente a presença de juvenis, fêmeas e machos ao longo de todo ano, além de uma reprodução contínua da espécie. Estes resultados ainda sugerem que a espécie parece ter um comportamento oportunista, podendo, inclusive, colonizar uma diversidade de substratos.

Population structure of the tanaid Sinelobus stanfordi (Richardson, 1901) (Crustacea, Tanaidacea) associated with roots of the water hyacinth Eichhornia azurea (Sw.) Kunth. (Liliiflorae, Pontederiaceae), from a coastal lagoon in Southern Brazil / Estrutura populacional do tanaídeo Sinelobus stanfordi (Richardson, 1901) (Crustacea, Tanaidacea) ocorrente em raízes do aguapé Eichhornia azurea (Sw.) Kunth. (Liliiflorae, Pontederiaceae), em uma laguna costeira do Sul do Brasil

This study aimed to investigate the population structure of Sinelobus stanfordi (Richardson, 1901) (Malacostraca, Tanaidae) in a coastal lagoon in the North coast in the Rio Grande do Sul state. The collections were performed weekly on banks of the aquatic hyacinth Eichhornia azurea (Sw.) Kunth during three months. Samples of water hyacinth were manually collected and washed on a sieve of 0.250μm mesh size. In the laboratory, the material was sorted and the tanaid lengths were measured and classified into following morphotype categories: Manca, Juveniles, Non- Reproductive Females (NRF), Preparatory Females (PREPF), Ovigerous Females (OVF) and Males. The distribution by frequency of body length classes presented a higher abundance of manca in the class of 0.75mm; juveniles in 2.19mm; non-reproductive females in 2.5mm; preparatory females in 2.7mm; ovigerous females in 2.85mm and males in 2.81mm. The average of sexual rate was 3.1:1 (females: males). It was observed the recruitment and predominance of juveniles in the eleven studied weeks, and the presence in lower proportion of PREPF, OVF and males. Based on the analyses of the population structure observed and data found in the literature, became evident the presence of juveniles, females and males during all the year, beyond a continuous reproduction activity of the species. The results have also suggested the species seems to have an opportunistic behavior, being able to colonize a high diversity of substrates.(AU)

Este trabalho buscou obter informações sobre a estrutura populacional de Sinelobus stanfordi (Richardson, 1901) (Malacostraca,Tanaidae), em intervalos semanais por um período de três meses, em uma laguna costeira do Litoral Norte do Rio Grande do Sul. As coletas foram realizadas em estande da macrófita aquática Eichhornia azurea (Sw.) Kunth. Exemplares do aguapé foram coletados manualmente e lavados sobre uma peneira de 0.250μm de abertura de malha. Em laboratório, o material foi triado e os indivíduos medidos e classificados por morfotipos: Mancas, Juvenis, Fêmeas Não-Reprodutivas (FNR), Fêmeas Preparatórias (FPREP), Fêmeas Ovadas (FOV) e Machos. A distribuição por frequências de classes de tamanho corporal demonstrou um maior número de indivíduos manca na classe de tamanho 0,75mm; juvenis, em 2,19mm; fêmeas não reprodutivas, em 2,5mm; fêmeas preparatórias, em 2,7mm; fêmeas ovadas, em 2,85mm e machos em 2,81mm. A média da proporção sexual foi de 3,1:1 (fêmeas:machos). Observou-se recrutamento e predomínio dos juvenis nas onze semanas de estudo e a presença, em menor proporção de FPREP, FOV e Machos. Com base na análise da estrutura populacional observada e dados encontrados na literatura, fica evidente a presença de juvenis, fêmeas e machos ao longo de todo ano, além de uma reprodução contínua da espécie. Estes resultados ainda sugerem que a espécie parece ter um comportamento oportunista, podendo, inclusive, colonizar uma diversidade de substratos.(AU)

Estructura de la comunidad de macroinvertebrados del arroyo Achiras (Córdoba, Argentina): análisis previo a la construcción de una presa

La regulación de ríos y arroyos mediante diques modifica parámetros que influyen directamente sobre la biota. En la cuenca endorreica Achiras-del Gato ha finalizado recientemente la construcción de una presa de mediana envergadura que alterará las características limnológicas del sistema y la estructura de las comunidades bentónicas. Este estudio aporta los primeros registros del macrobentos de este sistema lótico y analiza la variación espacio-temporal de la estructura de la comunidad en tramos pedemontanos del arroyo Achiras. Durante un año, antes de la construcción de la presa, se colectaron muestras de zoobentos y se registraron variables abióticas en correderas y rabiones de dos sitios del arroyo, uno situado río arriba del área del dique y otro aguas abajo de la misma. Para cada sitio, hábitat y estación del año se determinó abundancia, frecuencia, riqueza taxonómica, Índice de Shannon y equidad, y se analizaron mediante ANOVA de una y tres vías. Los atributos de las comunidades de referencia se complementaron con la determinación de taxa exclusivos e indicadores y detectores ecológicos. En el primer sitio se registraron 73 taxa, Simulium fue más abundante y Leptohyphes eximius Eaton, 1882, más frecuente. En el segundo se hallaron 75 taxa, Caenis fue más abundante y Cricotopus sp. 3 más frecuente. La abundancia y la riqueza fueron significativamente mayores en primavera, y la diversidad en rabiones de invierno. Se determinó que los atributos de la comunidad estuvieron afectados por la época de muestreo. El arroyo Achiras posee un régimen hídrico freático-pluvial, con caudales bajos en invierno y altos en verano, por lo que se esperan cambios en la biota nativa y la integridad del sistema en respuesta a la reducción de la variabilidad hidráulica cuando el funcionamiento de la presa altere el caudal natural.

Regulation of rivers and streams modifies parameters that directly influence on the biota. In Achiras-del Gato endorheic basin has completed the construction of a midsize dam that will alter the limnological characteristics of the system and the structure of benthic communities. This study provides the first taxonomic records of macrobenthos of this lotic system and analyzes the spatial and temporal variations of the community structure in the foothills stretches of Achiras stream. Zoobenthos samples were collected and abiotic variables were recorded in runs and riffles, during a year, in two sites located upstream and downstream of the dam area, prior to the dam was built. For each site, habitat and season we determined the abundance, frequency, taxonomic richness, Shannon and evenness, and the data were analyzed using one-way and three-way ANOVA. Attributes of the reference communities were complemented by the determination of ecological indicators and detectors, and exclusive taxa. In the first site 73 taxa were recorded, Simulium was the most abundant and Leptohyphes eximius Eaton, 1882, was the most frequent. In the second site we found 75 taxa, Caenis was the most abundant and Cricotopus sp. 3, was the most frequent. In this study composition and distribution of the biota and indicators taxa are discussed. We determined that the community attributes were affected by the hydrological periods in wich the samples were taken. Achiras stream has a phreatic-pluvial hydrological regime with low flows in winter and high flows in summer. Therefore, we expect changes in native biota and in system integrity in response to hydraulic variability reduction when Achiras dam start functioning and alters the natural flow.

Estructura de la comunidad de macroinvertebrados del arroyo Achiras (Córdoba, Argentina): análisis previo a la construcción de una presa

La regulación de ríos y arroyos mediante diques modifica parámetros que influyen directamente sobre la biota. En la cuenca endorreica Achiras-del Gato ha finalizado recientemente la construcción de una presa de mediana envergadura que alterará las características limnológicas del sistema y la estructura de las comunidades bentónicas. Este estudio aporta los primeros registros del macrobentos de este sistema lótico y analiza la variación espacio-temporal de la estructura de la comunidad en tramos pedemontanos del arroyo Achiras. Durante un año, antes de la construcción de la presa, se colectaron muestras de zoobentos y se registraron variables abióticas en correderas y rabiones de dos sitios del arroyo, uno situado río arriba del área del dique y otro aguas abajo de la misma. Para cada sitio, hábitat y estación del año se determinó abundancia, frecuencia, riqueza taxonómica, Índice de Shannon y equidad, y se analizaron mediante ANOVA de una y tres vías. Los atributos de las comunidades de referencia se complementaron con la determinación de taxa exclusivos e indicadores y detectores ecológicos. En el primer sitio se registraron 73 taxa, Simulium fue más abundante y Leptohyphes eximius Eaton, 1882, más frecuente. En el segundo se hallaron 75 taxa, Caenis fue más abundante y Cricotopus sp. 3 más frecuente. La abundancia y la riqueza fueron significativamente mayores en primavera, y la diversidad en rabiones de invierno. Se determinó que los atributos de la comunidad estuvieron afectados por la época de muestreo. El arroyo Achiras posee un régimen hídrico freático-pluvial, con caudales bajos en invierno y altos en verano, por lo que se esperan cambios en la biota nativa y la integridad del sistema en respuesta a la reducción de la variabilidad hidráulica cuando el funcionamiento de la presa altere el caudal natural.

Regulation of rivers and streams modifies parameters that directly influence on the biota. In Achiras-del Gato endorheic basin has completed the construction of a midsize dam that will alter the limnological characteristics of the system and the structure of benthic communities. This study provides the first taxonomic records of macrobenthos of this lotic system and analyzes the spatial and temporal variations of the community structure in the foothills stretches of Achiras stream. Zoobenthos samples were collected and abiotic variables were recorded in runs and riffles, during a year, in two sites located upstream and downstream of the dam area, prior to the dam was built. For each site, habitat and season we determined the abundance, frequency, taxonomic richness, Shannon and evenness, and the data were analyzed using one-way and three-way ANOVA. Attributes of the reference communities were complemented by the determination of ecological indicators and detectors, and exclusive taxa. In the first site 73 taxa were recorded, Simulium was the most abundant and Leptohyphes eximius Eaton, 1882, was the most frequent. In the second site we found 75 taxa, Caenis was the most abundant and Cricotopus sp. 3, was the most frequent. In this study composition and distribution of the biota and indicators taxa are discussed. We determined that the community attributes were affected by the hydrological periods in wich the samples were taken. Achiras stream has a phreatic-pluvial hydrological regime with low flows in winter and high flows in summer. Therefore, we expect changes in native biota and in system integrity in response to hydraulic variability reduction when Achiras dam start functioning and alters the natural flow.

Spatial-temporal distribution and recruitment of Stramonita haemastoma (Linnaeus, 1758) (Mollusca) on a sandstone bank in Ilhéus, Bahia, Brazil

We examined aspects of the population ecology of the gastropod Stramonita haemastoma at Ilhéus, Bahia, Brazil. We collected monthly from October 2007 through September 2008 on a sandstone bank 1.5 km long, on which two points and two sampling levels were defined. We took five previously randomised replicates at each level, using a square enclosing an area of 0.0625 m². The snails were photographed, counted, and measured at the site. Both recruits and other individuals in the population preferentially inhabit the regions closer to the lower shore, where they are submerged for longer periods and are less subject to physiological stresses caused by temperature variation and desiccation. The cracks and holes in the bank serve as refuges and places for S. haemastoma to lay their egg capsules. Recruits were observed throughout the study period, and the population showed continuous reproduction.

Neste estudo objetivou-se analisar aspectos da ecologia populacional do gastrópode Stramonita haemastoma em Ilhéus (Bahia). As amostragens foram realizadas mensalmente, entre outubro de 2007 e setembro de 2008, em um banco arenítico com 1,5 km de extensão, no qual foram estabelecidos dois pontos e dois níveis amostrais. Em cada nível foram feitas cinco repetições previamente aleatorizadas, utilizando-se um delimitador quadrado com 0,0625 m² de área. Os animais foram fotografados, quantificados e mensurados no local. Foi evidenciado que tanto recrutas quanto os demais indivíduos da população habitam preferencialmente as faixas mais próximas do infralitoral, onde, em função do maior tempo de submersão, os animais ficam menos sujeitos a estresses fisiológicos decorrentes de variação térmica e dessecação. Por apresentarem fendas e buracos, esses locais servem ainda de refúgio e ambiente para posturas de S. haemastoma. Foram observados recrutas ao longo de todo o período, evidenciando reprodução contínua.

Spatial-temporal distribution and recruitment of Stramonita haemastoma (Linnaeus, 1758) (Mollusca) on a sandstone bank in Ilhéus, Bahia, Brazil / Distribuição espaço-temporal e recrutamento de Stramonita haemastoma (Linnaeus, 1758) (Mollusca) em um banco arenítico de Ilhéus, Bahia, Brasil

We examined aspects of the population ecology of the gastropod Stramonita haemastoma at Ilhéus, Bahia, Brazil. We collected monthly from October 2007 through September 2008 on a sandstone bank 1.5 km long, on which two points and two sampling levels were defined. We took five previously randomised replicates at each level, using a square enclosing an area of 0.0625 m². The snails were photographed, counted, and measured at the site. Both recruits and other individuals in the population preferentially inhabit the regions closer to the lower shore, where they are submerged for longer periods and are less subject to physiological stresses caused by temperature variation and desiccation. The cracks and holes in the bank serve as refuges and places for S. haemastoma to lay their egg capsules. Recruits were observed throughout the study period, and the population showed continuous reproduction.

Neste estudo objetivou-se analisar aspectos da ecologia populacional do gastrópode Stramonita haemastoma em Ilhéus (Bahia). As amostragens foram realizadas mensalmente, entre outubro de 2007 e setembro de 2008, em um banco arenítico com 1,5 km de extensão, no qual foram estabelecidos dois pontos e dois níveis amostrais. Em cada nível foram feitas cinco repetições previamente aleatorizadas, utilizando-se um delimitador quadrado com 0,0625 m² de área. Os animais foram fotografados, quantificados e mensurados no local. Foi evidenciado que tanto recrutas quanto os demais indivíduos da população habitam preferencialmente as faixas mais próximas do infralitoral, onde, em função do maior tempo de submersão, os animais ficam menos sujeitos a estresses fisiológicos decorrentes de variação térmica e dessecação. Por apresentarem fendas e buracos, esses locais servem ainda de refúgio e ambiente para posturas de S. haemastoma. Foram observados recrutas ao longo de todo o período, evidenciando reprodução contínua.

Seasonal variability on the structure of sublittoral macrozoobenthic association in the Patos Lagoon estuary, southern Brazil

The aim of this study is to analyze and relate the spatial-temporal variability of macrozoobenthic assemblages to bottom characteristics and salinity fluctuations, in an estuarine shallow water region of Patos Lagoon. Monthly samples, between September 2002 and August 2003, were taken on six sampling stations (distant 90 m). Three biological samples with a 10 cm diameter corer, one sample for sediment analysis, fortnightly bottom topography measurements, and daily data of temperature and salinity were taken from each station. Two biotic and environmental conditions were identified: the first corresponding to spring and summer months, with low macrozoobenthos densities, low values of salinity, small variations in bottom topographic level and weak hydrodynamic activity. A second situation occurred in the months of fall and winter, which showed increased salinity, hydrodynamics and macrobenthos organisms. These results which contrast with previous studies carried out in the area, were attributed to failure in macrozoobenthos recruitments during summer period, especially of the bivalve Erodona mactroides Bosc, 1802 and the tanaid Kalliapseuses schubartii Mañe-Garzón, 1949. This results showed that recruitments of dominant species were influenced by salinity and hydrodynamic conditions.

Objetiva-se analisar e relacionar a variabilidade espaço-temporal de uma associação macrozoobentônica com as características do substrato e variações da salinidade, numa enseada da região estuarina da Lagoa dos Patos. Amostragens mensais entre setembro de 2002 e agosto de 2003 foram realizadas em seis pontos de coleta distantes 90 m entre si. Em cada ponto foram tomadas três amostras biológicas com tubo extrator de 10 cm de diâmetro, uma amostra para análise do sedimento, medidas quinzenais da topografia do fundo e dados diários de temperatura e salinidade. Foram identificadas duas situações ambientais e bióticas bem definidas: uma correspondente aos meses de primavera e verão com baixas densidades do macrozoobentos, baixos valores de salinidade e pouca variação no nível do substrato, refletindo neste caso uma menor atividade hidrodinâmica. A outra situação ocorreu nos meses de outono e inverno, que mostrou uma situação oposta em relação às variáveis bióticas e abióticas. Esses resultados, que contrariam trabalhos anteriores efetuados na região, foram atribuídos a falhas nos recrutamentos do macrozoobentos durante o período de verão, especialmente do bivalve Erodona mactroides Bosc, 1802 e do tanaidáceo Kalliapseudes schubartii Mañe-Garzón, 1949. Verificou-se que os recrutamentos das espécies dominantes foram influenciados pelas condições de salinidade e pela hidrodinâmica.

Seasonal variability on the structure of sublittoral macrozoobenthic association in the Patos Lagoon estuary, southern Brazil

The aim of this study is to analyze and relate the spatial-temporal variability of macrozoobenthic assemblages to bottom characteristics and salinity fluctuations, in an estuarine shallow water region of Patos Lagoon. Monthly samples, between September 2002 and August 2003, were taken on six sampling stations (distant 90 m). Three biological samples with a 10 cm diameter corer, one sample for sediment analysis, fortnightly bottom topography measurements, and daily data of temperature and salinity were taken from each station. Two biotic and environmental conditions were identified: the first corresponding to spring and summer months, with low macrozoobenthos densities, low values of salinity, small variations in bottom topographic level and weak hydrodynamic activity. A second situation occurred in the months of fall and winter, which showed increased salinity, hydrodynamics and macrobenthos organisms. These results which contrast with previous studies carried out in the area, were attributed to failure in macrozoobenthos recruitments during summer period, especially of the bivalve Erodona mactroides Bosc, 1802 and the tanaid Kalliapseuses schubartii Mañe-Garzón, 1949. This results showed that recruitments of dominant species were influenced by salinity and hydrodynamic conditions.

Objetiva-se analisar e relacionar a variabilidade espaço-temporal de uma associação macrozoobentônica com as características do substrato e variações da salinidade, numa enseada da região estuarina da Lagoa dos Patos. Amostragens mensais entre setembro de 2002 e agosto de 2003 foram realizadas em seis pontos de coleta distantes 90 m entre si. Em cada ponto foram tomadas três amostras biológicas com tubo extrator de 10 cm de diâmetro, uma amostra para análise do sedimento, medidas quinzenais da topografia do fundo e dados diários de temperatura e salinidade. Foram identificadas duas situações ambientais e bióticas bem definidas: uma correspondente aos meses de primavera e verão com baixas densidades do macrozoobentos, baixos valores de salinidade e pouca variação no nível do substrato, refletindo neste caso uma menor atividade hidrodinâmica. A outra situação ocorreu nos meses de outono e inverno, que mostrou uma situação oposta em relação às variáveis bióticas e abióticas. Esses resultados, que contrariam trabalhos anteriores efetuados na região, foram atribuídos a falhas nos recrutamentos do macrozoobentos durante o período de verão, especialmente do bivalve Erodona mactroides Bosc, 1802 e do tanaidáceo Kalliapseudes schubartii Mañe-Garzón, 1949. Verificou-se que os recrutamentos das espécies dominantes foram influenciados pelas condições de salinidade e pela hidrodinâmica.

Bivalve mollusk assemblages on São Paulo's northern continental shelf, southeast Brazil

Soft bottom bivalve mollusc assemblages were sampled along a depth gradient (10 to 100 m) on the northern São Paulo shelf during the austral summer and winter. A one-way analysis of similarity permutation test revealed there was no seasonal difference in the structure of the bivalve assemblages in the area. A clustering analysis indicated 3 groups of stations corresponding to the bathymetric gradient. Both K-dominance curves and Shannon and Pielou indexes showed higher biological diversity and higher evenness for the shallower area. Most of the bivalves found were classified as suspension-feeders, co-occurring with deposit-feeder species, suggesting an absence of negative interactions between these trophic groups. Differences in the frequency of disturbance along the depth gradient caused by wave storms - more common in winter - and also by predation and anthropogenic activities, such as dredging of fishing boats and input of gross sewage, likely explain the higher diversity found on the inner shelf of Ubatuba.

Moluscos bivalves de fundos não-consolidados foram amostrados no verão e no inverno entre as profundidades de 10 a 100 m na plataforma norte de São Paulo. Baseado na análise de variância por similaridade não foi verificada diferença sazonal significativa nas associações de bivalves. A análise de agrupamento evidenciou três grupos de estações que correspondem ao gradiente batimétrico. Tanto as curvas de dominância-K, quanto os índices biológicos usados (Shannon e Pielou) mostraram uma maior diversidade biológica e uma maior uniformidade na distribuição dos indivíduos nas áreas rasas. A maioria dos bivalves coletados pode ser classificada como de hábito alimentar suspensívoro. Estes, porém, co-ocorreram com espécies depositívoras, o que sugere uma ausência de correlação negativa entre esses dois grupos tróficos. Diferenças na freqüência de ocorrência de distúrbios ao longo do gradiente batimétrico, causados por ondas de tempestade, mais comuns no inverno, e também causados por predação e atividades antrópicas, tais como dragagens realizadas por barcos de pesca e despejo de esgoto in natura, podem explicar os padrões de diversidade observados.

Effects of dredging operations on soft bottom macrofauna in a harbor in the Patos Lagoon estuarine region of southern Brazil

An evaluation was made of the effects of dredging on the soft bottom community in the channel of the Rio Grande harbor in the Patos Lagoon estuarine region of southern Brazil. During four seasonal cruises, samples were collected from nine biological stations, one of which was located outside the dredged area. Three macrobenthic samples were collected on each cruise from each station, using a 0.08 m² van Veen grab. A cluster analysis was applied to group summer and autumn cruise stations before the dredging period, revealing larger numbers of species (35-36 spp.) and higher densities of organisms. The station located outside the dredging area was always included in this group, regardless of the sampling period or conditions of salinity. Another group comprised the winter and spring stations during the dredging period. This group was characterized by stations with the fewest species (20-18 spp.) and the lowest and most variable organism densities. The efficient strategies of resilience of the dominant estuarine species may minimize the effects of dredging on the biota through the rapid recolonization of the soft bottom of the harbor channel.

Objetiva-se avaliar a resposta da associação de macroinvertebrados bentônicos ao efeito de dragagens do canal de acesso ao Porto de Rio Grande, na região estuarina da Lagoa dos Patos, RS, Brasil. Foram tomadas 3 amostras em nove estações de coleta, durante quatro cruzeiros sazonais. Uma das estações foi posicionada a montante da área dragada. As coletas foram efetuadas com um pegador van Veen de 0,08 m². A análise de classificação (Similaridade Bray-Curtis) agrupou as estações de verão e outono, realizadas antes do início das dragagens, as quais mostraram maiores valores do número de espécies (35-36 spp) e das densidades do macrozoobentos. A estação localizada a montante da área de dragagem esteve sempre incluída neste grupo, independente do período de amostragem ou das condições de salinidade na região estuarina. Um segundo grupo incluiu as estações realizadas na primavera e no inverno, que coincidiram com o período de dragagem. Estas estações apresentaram menor número de espécies (20-18 spp.) e densidades, mas com um aumento da variância. A eficiente estratégia de resiliência das espécies estuarinas dominantes pode minimizar o efeito da dragagem sobre a biota, através de uma rápida recolonização das áreas dragadas no canal de acesso ao Porto de Rio Grande.

Spatial distribution of the macrozoobenthos in the Solís Grande Stream estuary (Canelones-Maldonado, Uruguay)

The analysis of 24 quantitative macrobenthic samples taken from the Solís Grande Stream estuary yielded 10 species from a total of 4,446 individuals. It was verified that both species richness and diversity was lower than those recorded in nearby regions with similar environmental conditions. In contrast with other studies, a marked dominance of any of the present species was not verified. All the species recorded correspond to typical estuarine organisms. Abundance data were analysed with multivariate techniques and the results showed a relationship with salinity, mean diameter and the percentage of fine sand. According to the cluster analysis and the canonical correspondence analysis (CCA) four groups of stations were defined. The partition out of total variation of the species data showed that the amount of variation explained by the space alone was low. Spatial patterns observed and their possible causes are analysed and discussed in relation to the natural factors that acts in this coastal ecosystem.

A análise de 24 amostras quantitativas de macrobentos do estuário do Arroio Solís Grande revelou 10 espécies e um total de 4.446 organismos. A riqueza de espécies e a diversidade foram menores do que as registradas em regiões vizinhas com características ambientais similares. Em contraste com outros estudos, não se verificou grande dominância de nenhuma das espécies presentes. Todas são organismos tipicamente estuarinos. Os dados de abundância foram tratados com técnicas estatísticas multivariadas e os resultados mostraram relação com a salinidade, o diâmetro médio e a porcentagem de areia fina do sedimento. Tanto a análise de agrupamento quanto a análise de correspondência canônica (CCA) revelaram quatro grupos de estações dentro do estuário. A análise de divisão da variação total dos dados mostrou que a variabilidade em decorrência do espaço foi baixa. Os padrões espaciais observados e suas possíveis causas são analisados e discutidos em relação aos fatores naturais que atuam nesse ecossistema costeiro.

The use of macrobenthos as indicators of the water quality of mountain Rivers of Parque Estadual de Campos do Jordão, SP / Organismo bentônicos como indicadores da qualidade da água de rios do parque estadual de campos do jordão, sp

The benthic community of four rivers of "Parque Estadual de Campos do Jordão", in an amount of five sections was studied through monthly collects from March 1984 to February 1985 with the purpose of to use the macrobenthic organisms as indicators of the water quality. A comparison among sections was done through physical and chemical characters of the water and the environmental indicators such as Diptera (Chironomus, Tanytarsini, Orthocladiinae), Trichoptera and Ephemeroptera, the diversity index of organisms and percentage of similarity using the different groups of Diptera and, particularly, Chronomidae. Thus, it can be concluded that Canhambora and Casquilho streams are the least polluted environments and that Sapucaí-Guaçu River is quite different from the others and less favorable for fish life.

Foi estudada a comunidade bentônica de 4 rios do Parque Estadual de Campos do Jordão, num total de 5 setores, através de coletas mensais no período de março de 1984 a fevereiro de 1985, com objetivo de utilizar o macrobentos como indicador da qualidade da água. A comparação entre os setores foi feita através de dados físicos e químicos da água e dos organismos indicadores de ambiente, como, principalmente, Diptera (Chironomus, Tanytarsini, Orthocladiinae), Trichoptera e Ephemeroptera, da diversidade de grupos de organismos da comunidade bentônica e da porcentagem de similaridade através dos grupos identificados de Diptera e de Chironomidae. Pode-se concluir que os ambientes menos poluídos são o Córrego Canhambora e o Ribeirão Casquilho e que o Rio Sapucaí-Guaçu é o que menos semelhança apresenta com os outros rios, constituindo o ambiente menos favorável à vida dos peixes.