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Introduction: Aquatic ecosystems in southern Brazil are presently under great environmental pressure. Changes in land use result in negative impacts on the ecosystem, affecting the functioning of stream communities. Objective: To compare the benthic macroinvertebrate community richness, abundances and compositions in streams of three South Brazilian grassland landscapes and correlate community patterns with environmental and spatial variables. Methods: Fifteen streams along riparian forests were selected in three landscapes (mean geographical distance of 285.1 km) inserted in the Paraná and Uruguai river basins. Of the three landscapes, two are inserted in conservation units (State Park of Guartelá and Palmas Wildlife Refuge). Invertebrates were collected in 20 kick net points along 150 m of the streams between June and November 2015. Invertebrates were sorted in the laboratory with three sieves and were identified to the lowest taxonomic level possible. The taxa were classified in functional feeding groups of shredders/detritivores, predators, scrapers, collectors/filters and gatherers/collectors. For each stream, we measured the environmental variables width and velocity, pH, dissolved oxygen, and temperature; and the relative cover of forest, grassland, plantation and silviculture in the catchments. Results: We found a total of 1 058 individuals, divided in 53 morphospecies and 34 families. Lower abundance of benthic macroinvertebrates was found in the northernmost landscape with higher temperature, and forest in the catchment. These streams were described mainly by predator groups, while streams inserted in the other two landscapes showed a more diverse guild composition of shredders/detritivores, gatherers/collectors, collectors/filterers, and scrapers. Geographical distance was the main factor influencing differences in community compositions among landscapes. Conclusions: Lower abundance of the northernmost landscape may be explained by (i) the low habitat heterogeneity due to dominance of sandy substrates, and by (ii) the anthropogenic land use of agriculture and extensive cattle breeding in the region that is ongoing and started before the creation of the conservation unit. Additionally, composition of macroinvertebrates may be correlated with environmental differences among landscapes that, in turn, are related to the geographical distance. Therefore, macroinvertebrate community responses may reflect different biota biogeographical histories that can also be associated with historical land use practices.

Introducción: Los ecosistemas acuáticos en el sur deBrasil están actualmente bajo gran presión ambiental. Cambios en el uso de la tierra pueden tener impactos negativos en el ecosistema que afectan el funcionamiento de las comunidades de arroyos. Objetivo: Comparar la riqueza, abundancia y las composiciones de macroinvertebrados bentónicos en arroyos de tres paisajes de pastizales del sur de Brasil, y correlacionar los modelos patrones de comunidad con variables ambientales y espaciales. Metodología: Quince arroyos a lo largo de los bosques ribereños fueron seleccionados en tres paisajes (distancia geográfica media de 285.1 km) insertados en las cuencas fluviales de Paraná y Uruguai. De los tres paisajes, dos están insertados en unidades de conservación (Parque Estatal de Guartelá y Refugio de Vida Silvestre de Palmas). Los invertebrados fueron recolectados en 20 puntos con una red a lo largo de 150 m de las corrientes entre junio y noviembre 2015. En el 2016, fueron clasificados en el laboratorio, con tres tamices de mallas, identificándolos al nivel taxonómico más bajo posible. Así, los taxones se clasificaron en grupos funcionales alimentícios: trituradores/detritívoros, depredadores, raspadores, colectores/filtradores y colectores/recolectores. En cada arroyo fueron medidas las variables ambientales: anchura, velocidad, pH, oxígeno disuelto y temperatura; en las cuencas, la cubierta relativa de bosques, pastizales, plantaciones y silvicultura. Resultados: Encontramos un total de 1 058 individuos, divididos en 53 morfoespecies y 34 familias. Se encontró una menor abundancia de macroinvertebrados bentónicos en el paisaje más septentrional con mayor temperatura, y bosques en la cuenca. Esos arroyos fueron descritos principalmente por grupos de depredadores, mientras que los arroyos insertados en los otros dos paisajes mostraron una composición más diversa de trituradores/detritívoros, colectores/recolectores, colectores/filtradores y raspadores. La distancia geográfica fue el principal factor que influyó en las diferencias de las composiciones comunitarias entre los paisajes. Conclusiones: La menor abundancia encontrada en el paisaje más septentrional puede explicarse por (i) la baja heterogeneidad constatada en el hábitat, debido al dominio de los sustratos arenosos, y por (ii) el uso antropogénico de la tierra: la agricultura y la cría extensiva de ganado en la región que está en curso, la cual comenzó antes de la creación de la unidad de conservación. Además, la composición de los macroinvertebrados puede estar correlacionada con diferencias ambientales entre paisajes que, a su vez, están relacionadas con la distancia geográfica. Por lo tanto, las respuestas comunitarias de los macroinvertebrados pueden reflejar diferentes historias biogeográficas de biotas que también pueden estar asociadas a prácticas históricas de uso de la tierra.

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Resumen Las quebradas están fuertemente influenciadas por su vegetación ribereña y la deforestación afecta a la comunidad acuática. Se estudiaron los efectos de la deforestación sobre la diversidad taxonómica y funcional del ensamblaje de macroinvertebrados acuáticos en cuatro quebradas Andinas colombianas. El estudio incluyó 12 sitios, siete de ellos con cobertura arbórea en sus márgenes en áreas boscosas no perturbadas por la deforestación (estaciones de referencia) y los otros cinco sin cobertura arbórea en áreas deforestadas (estaciones alteradas). Se realizaron cuatro muestreos de campo entre junio 2011 y febrero 2012 y se recolectaron muestras de macroinvertebrados bentónicos utilizando el método D-net con malla de 500 μm y recolección manual, y se midieron diferentes variables fisicoquímicas in situ. Se calcularon los índices de Shannon-Wienner (H ') y Simpson (D). Se aplicaron análisis unidireccionales de varianza ANOVAs a cada variable ambiental y análisis canónicos discriminantes (CDA). Se recolectaron un total 8 370 individuos correspondientes a 80 taxones durante el estudio. La abundancia y diversidad fue mayor en las estaciones localizadas en áreas boscosas no perturbadas. Thraulodes, Anacroneuria y Rhagovelia, se asociaron con valores más altos de Calidad de Bosque de Ribera Andina (QBR-And), Índice de Hábitat Fluvial (IHF), Biological Monitoring Working Party Colombia (BMWP/Col) y temperatura en estaciones de referencia, mientras que Leptonema, Baetodes y Mayobaetis se asociaron con mayores valores de pH y altura sobre nivel del mar en estaciones alteradas. Los principales grupos funcionales tróficos (GFT) en las estaciones de referencia fueron colectores-recolectores/raspadores (27.2 %), raspadores (25.4 %) y depredadores (24.4 %), mientras que en estaciones alteradas fueron: Colectores filtradores (27.5 %), colectores-recolectores/raspadores (17.4 %) y raspadores (15.7 %). Los hábitos de vida más abundantes en las estaciones de referencia fueron agarradores (50.5 %), taxones con tres o más hábitos (28.7 %) y patinadores (16.1 %), mientras que en las estaciones alteradas fueron agarradores (68.1 %), taxones con tres o más hábitos (13.7 %) y excavadores (5.2 %). El conocimiento de las variables que determinan la estructura taxonómica y funcional de los ensamblajes de macroinvertebrados, y cómo responden a impactos como la deforestación, puede ayudar a determinar acciones de protección o restauración de las condiciones ambientales y ecológicas de las quebradas Andinas y los hábitats riparios.(AU)

Abstract The creeks are strongly influenced by their riparian vegetation, and the deforestation affect the aquatic community. The effects of deforestation on taxonomic and functional diversity of aquatic macroinvertebrate assemblage in four Colombian Andean creeks were evaluated. The study included 12 sites, seven of them with arboreal coverage at their margins in forested areas undisturbed by deforestation (reference stations) and the other five without tree cover in deforested areas (altered stations). Four field samplings were carried out between June 2011 and February 2012, and samples of benthic macroinvertebrates were collected using the D-net method with 500 μm mesh and manual collection, and different physicochemical variables were measured in situ. The Shannon-Wienner (H′) and Simpson´s index (D) were calculated. One-way analyses of variance (ANOVAs) to each environmental variable, and canonical discriminant analysis (CDA) to establish differences in environmental variables, taxonomic and functional diversity between references and altered stations were applied. 8 370 macroinvertebrate individuals corresponding to 80 taxa were collected in the study, with 6 758 individuals and 75 taxa in references stations and 1 612 individuals and 50 taxa in altered stations. The reference stations had higher values of diversity and the taxa that made major contributions to the variance between reference and altered stations were Thraulodes, Anacroneuria and Rhagovelia, which were associated with the highest values of Index of Andean riparian vegetation Quality (QBR-And), fluvial habitat index (IHF), Biological Monitoring Working Party Colombia BMWP/Col, EPT index (Ephemeroptera, Plecoptera, and Trichoptera) and temperature in reference stations, whereas Leptonema, Baetodes and Mayobaetis were associated with higher pH and elevation above sea level in altered stations. The main functional feeding groups (FFG) at the reference stations were collectors-gatherers/scrapers CG / SC (27.2 %), scrapers SC (25.4 %) and predators PR (24.4 %), and for altered stations were collectors-filterers CF (27.5 %), collectors-gatherers/scrapers CG / SC (17.4 %) and scrapers SC (15.7 %). The most abundant life habits were clingers Cg (50.5 %), taxa with three or more habits (28.7 %) and skaters Sk (16.1 %), in the reference stations, and clingers Cg (68.1 %), taxa with three or more habits (13.7 %) and burrowers Bu (5.2 %) in the altered stations. The knowledge of the variables that determine the taxonomic and functional structure of the macroinvertebrate assemblages, and how they respond to impacts such as deforestation, can help to determine actions of protection or restoration of the environmental and ecological conditions of the Andean streams and the riparian habitats.(AU)

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Abstract Macroinvertebrate shredders have been widely recognized as an important functional feeding group that contributes to leaf decomposition in temperate streams, but little is known about their role in upland Neotropical streams. In this study, we investigated the effect of macroinvertebrate exclusion on leaf breakdown rates in two upland streams in Colombia. The study was carried out between January and April of 2009, including the dry season and the beginning of the wet season. We measured leaf mass loss using coarse- (15 mm; accessible to macroinvertebrates) and fine- (200 µm; macroinvertebrates excluded) mesh litter bags that were anchored with wood stakes to the bottom of each stream and recovered after 7, 14, 21, 28, and 56 days. We selected leaves from two dominant plant species and used three leaf treatments: two single species (Palicourea cuatrecasasii and Critoniopsis ursicola) and mixed-species (P. cuatrecasasii and C. ursicola). We compared leaf breakdown rates between the Peña Bonita and Marianela stream, mesh-sizes, and leaf treatments. Macroinvertebrates that colonized the litter bags were measured for density and biomass and categorized in functional feeding groups. In general, there were no significant differences in breakdown rates between the streams and the mesh-sizes. In contrast, leaf breakdown rates had significant differences between all leaf species, where C. ursicola had higher breakdown rates than mixed-species, and P. cuatrecasasii. Macroinvertebrate exclusion did not affect leaf breakdown rates and their assemblages were composed by high densities of collectors (mainly Chironomidae) and few shredders with a large body size. The similar macroinvertebrate colonization between leaf species, the relatively slow breakdown rates, and the shredder scarcity, suggest that leaves were a refractory substrate. Further studies should include leaf species with different nutritional qualities and larger spatial-temporal scales to test the hypothesis of shredder presence and its role on leaf decomposition in upland Colombian streams. Rev. Biol. Trop. 66(1): 457-467. Epub 2018 March 01.

Resumen Los macroinvertebrados fragmentadores han sido ampliamente reconocidos como un importante grupo funcional alimenticio que contribuye a la descomposición de la hojarasca en quebradas del hemisferio norte, pero poco se sabe sobre su papel en quebradas de montaña neotropicales. En el presente estudio investigamos el efecto de la exclusión de los macroinvertebrados sobre las tasas de fragmentación de la hojarasca en dos quebradas de montaña en Colombia. Nuestra hipótesis es que la fragmentación de la hojarasca es mediada principalmente por macroinvertebrados fragmentadores en quebradas de montaña en Colombia. Este estudio fue llevado a cabo entre enero y abril 2009, incluyendo la época seca y el comienzo de la época de lluvias. Se midieron las pérdidas de masa de hojarasca usando bolsas de malla gruesa (15 mm; accesible a macroinvertebrados) y fina (200 µm; macroinvertebrados excluidos); estas fueron atadas con estacas de madera al fondo de cada quebrada y recuperadas transcurridos 7, 14, 21, 28 y 56 días. Se seleccionó hojarasca de dos especies dominantes en los sitios de estudio y se usaron tres tratamientos para las bolsas de hojarasca: Critoniopsis ursicola, Palicourea cuatrecasasii y una mezcla de estas dos especies. Se compararon las tasas de fragmentación de la hojarasca entre las dos quebradas, los dos tipos de malla y las especies de hojarasca. Los macroinvertebrados que colonizaron las bolsas de hojarasca fueron medidos en términos de densidad, biomasa y categorizados en grupos funcionales alimenticios. En general, nuestros resultados no mostraron diferencias significativas en las tasas de fragmentación de la hojarasca entre las quebradas y entre los tipos de malla. En contraste, las tasas de fragmentación presentaron diferencias significativas entre las especies de hojarasca; específicamente, C. ursicola tuvo tasas más altas de fragmentación que las especies mezcladas y que P. cuatrecasasii. Con respecto a los macroinvertebrados, el presente estudio encontró que su exclusión no tuvo un efecto sobre las tasas de fragmentación y los ensamblajes estuvieron compuestos por una alta densidad de recolectores (principalmente de la familia Chironomidae) y pocos fragmentadores con gran tamaño corporal. La colonización similar de macroinvertebrados entre las especies de hojarasca, las relativamente lentas tasas de fragmentación, sugieren que las hojas fueron un sustrato refractario. Futuros estudios deberían incluir especies de hojarasca con diferentes calidades nutricionales y una mayor escala espacio-temporal para estudiar la hipótesis de la presencia de fragmentadores en quebradas de montaña en Colombia.

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Resumen: La determinación de los hábitos alimentarios permite la comprensión de muchos procesos ecológicos que se dan en los ecosistemas lóticos. El objetivo de este trabajo es: 1) conocer los hábitos alimentarios de ninfas de Claudioperla tigrina en un amplio gradiente altitudinal y latitudinal en Argentina; 2) asignar el grupo funcional trófico (GFT) de C. tigrina; 3) evaluar diferencias entre dietas de los sitios estudiados. Las ninfas estudiadas fueron recolectadas a lo largo de un amplio rango espacial en el noroeste de Argentina e incluyen diferentes estados del desarrollo (cuatro clases de tamaño). El material ingerido fue extraído de la parte anterior del tubo digestivo mediante disección ventral del tórax. Los perfiles dietarios fueron analizados a través de la estimación de parámetros de la distribución multinomial de Dirichlet. Se efectuaron ANOVA's para cada rubro alimentario en función de los sitios. Se utilizó la técnica Multidimensional Scaling (MDS) para identificar los sitios con perfiles alimentarios promedios similares. Se realizó un análisis de amplitud de nicho trófico para evaluar la diversificación de los recursos consumidos en cada sitio. El aparato bucal no muestra variaciones a lo largo del desarrollo ninfal, excepto una mayor esclerotización con la edad. Poseen palpos mandibulares y maxilares relativamente cortos y mandíbulas y maxilas fuertes, esclerozadas y dentadas. Las ninfas ingirieron más de un ítem alimentario, sugiriendo que se trata de una especie flexible en su alimentación. El ítem dominante en la dieta fue la MOPG, los signos de haber sido masticado indican hábitos trituradores. Se encontraron diferencias entre sitios para los ítems MOPF, invertebrados, algas y sedimento, pero no para MOPG. Se obtuvieron las correlaciones para cada eje del análisis MDS. Con el eje 1 se correlacionaron negativamente los sitios AP, LT, LI, C y M (Selva de Yungas y Pastizal de neblina) asociados a un mayor consumo de MOPF, en el lado positivo del eje se encontró el sitio P (Altos Andes) asociado a los ítems invertebrados y sedimento. Para el eje 2 se relacionaron positivamente IN (Pastizal neblina) y LR (Monte de Sierras y Bolsones) con la presencia de algas. Los resultados del análisis de amplitud de nicho revelaron diferencias en el uso de los recursos secundarios de la dieta en los sitios estudiados que puede deberse a la oferta ambiental en las ecorregiones consideradas. El GFT de C. tigrina es triturador/ recolector en Selva de Yungas y Pastizales de Neblina y triturador/ depredador en Altos Andes. La definición del GFT de C. tigrina y el establecimiento de su rol como procesador primario de materia orgánica representa un paso importante para futuros estudios de redes tróficas y otras metodologías basadas en los grupos funcionales.

Abstract: Dietary information gives insight into several ecological processes acting in lotic ecosystems. This work aimed: 1) to identify the dietary habits of Claudioperla tigrina immature stages along a wide altitudinal as well as latitudinal gradient in North Argentina; 2) to define the functional feeding group (FFG) of C. tigrina; 3) to evaluate differences in diet in the studied sites. Studied nymphs were collected from localities widely scattered in Northwestern Argentina and they fell into different developmental stages (four size classes). The ingested material was extracted from the foregut and midgut by using thorax ventral dissection. Dietary profiles were analyzed through the estimation of parameters associated with a Dirichletmultinomial distribution. ANOVA's were performed for each food item using sites as factor. Multidimensional Scaling was used to identify sites with similar dietary profiles. An analysis of food-niche breadth was also performed to evaluate the degree of dietary diversification for the resources consumed in each site. Mouthparts are similar across the different size classes, excepting the increasing sclerotization recorded with age. Mouthparts retained most of the typical chewing groundplan, showing relatively short labial and maxillar palps, and strong, sclerotized and denticulated mandibles and maxillae. Our results pointed out that the nymphs of C. tigrina always ingest two or more food items (CPOM, FPOM, invertebrates and algae), suggesting thus a flexible diet. The diet changed in relation to body size, while finer particles were consumed in the early stages, larger particles were ingested in final stages. Coarse particulate organic matter was the dominant food item, with signals of shredding during ingestion. Differences between sites for FPOM, invertebrates, algae and sediment were detected, but not for MOPG. Correlations were obtained for the first two axis of the MDS analysis. Sites AP, LT, LI, C and M (Yungas Rainforest and Humid Grassland) were negatively correlated with the axis 1 which was associated with increased consumption of FPOM. On the positive side of the axis the site P (High Andes) is associated with a greater proportion of invertebrates and sediment. The sites IN (Humid Grassland) and LR (Argentine Northwest Monte and Thistle of the Prepuna) were located at the positive domain of axis 2 which is in turn associated with a greater count of algae in the dietary contents. We found significant differences in the quantity of secondary items, and this is likely related with the resources environmental availability. The FFG of Claudioperla tigrina is primarily shredder/collector-gatherer in Yungas Rainforest and Humid Grassland shredder/predator in High Andes. FFG classification of C. tigrina and the definition of their role for organic matter processing is an important step for future studies based on functional groups such as analysis of food webs. Rev. Biol. Trop. 65 (3): 1174-1184. Epub 2017 September 01.

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

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Stream ecology studies see to understand ecological dynamics in lotic systems. The characterization of streams into Functional Process Zones (FPZ) has been currently debated in stream ecology because aquatic communities respond to functional processes of river segments. Therefore, we tested if different functional process zones have different number of genera and trophic structure using the aquatic insect community of Neotropical streams. We also assessed whether using physical and chemical variables may complement the approach of using FPZ to model communities of aquatic insects in Cerrado streams. This study was conducted in 101 streams or rivers from the central region of the state of Goiás, Brazil. We grouped the streams into six FPZ associated to size of the river system, presence of riparian forest, and riverbed heterogeneity. We used Bayesian models to compare number of genera and relative frequency of the feeding groups between FPZs. Streams classified in different FPZs had a different number of genera, and the largest and best preserved rivers had an average of four additional genera. Trophic structure exhibited low variability among FPZs, with little difference both in the number of genera and in abundance. Using functional process zones in Cerrado streams yielded good results for Ephemeroptera, Plecoptera, and Trichoptera communities. Thus, species distribution and community structure in the river basin account for functional processes and not necessarily for the position of the community along a longitudinal dimension of the lotic system.

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Leaf litter decomposition in six Cloud Forest streams of the upper La Antigua watershed, Veracruz, Mexico. Leaf litter decomposition is an important stream ecosystem process. To understand factors controlling leaf decomposition in cloud forest in Mexico, we incubated leaf packs in different streams along a land use cover gradient for 35 days during the dry and wet seasons. We assessed relations between leaf decomposition rates (k), stream physicochemistry, and macroinvertebrates colonizing leaf packs. Physicochemical parameters showed a clear seasonal difference at all study streams. Leaves were colonized by collector-gatherer insects, followed by shredders. Assessment of factors related to k indicated that only forest cover was negatively related to leaf decomposition rates. Thus stream physicochemistry and seasonality had no impact on decomposition rates. We concluded that leaf litter decomposition at our study streams is a stable process over the year. However, it is possible that this stability is the result of factors regulating decomposition during the different seasons and streams. Rev. Biol. Trop. 62 (Suppl. 2): 111-127. Epub 2014 April 01.

Para muchos arroyos, la hojarasca proveniente de la zona ribereña es la base de las redes tróficas, por lo cual el proceso de descomposición de la hojarasca es de gran importancia para el funcionamiento de estos ecosistemas. Con el fin de conocer los factores que afectan la descomposición de la hojarasca en arroyos del bosque mesófilo de montaña (BMM), se utilizaron paquetes de hojarasca durante 35 días. Seis arroyos con un gradiente de perturbación fueron estudiados en la época seca y lluviosa. Se determinó la relación entre la tasa de descomposición de la hojarasca (k), con algunos parámetros fisicoquímicos del cuerpo de agua y los macroinvertebrados colonizadores de los paquetes. Los factores fisicoquímicos mostraron una separación de los cuerpos de agua según la época a través de un Análisis de Componentes Principales (ACP). De los insectos colonizadores de los paquetes de hojarasca, el grupo funcional de los recolectores fue el más abundante, seguido por los fragmentadores. Solo se encontró una relación negativa entre la k y el porcentaje de cobertura boscosa (p=0.04) al realizar una regresión múltiple por pasos en la que se incluyeron algunos parámetros fisicoquímicos, el porcentaje de cobertura boscosa y las abundancias promedio de los insectos fragmentadores y no fragmentadores. La descomposición de la hojarasca en los arroyos estudiados parece ser un proceso estable a lo largo del año, aunque los factores responsables por la regulación pueden diferir en las distintas épocas.

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Despite the fact that little is known about the consequences of hydropower production in tropical areas, many large dams (>15m high) are currently under construction or consideration in the tropics. We researched the effects of large hydroelectric dams on aquatic macroinvertebrate assemblages in two Costa Rican rivers. We measured physicochemical characteristics and sampled aquatic macroinvertebrates from March 2003 to March 2004 in two dammed rivers, Peñas Blancas and San Lorenzo, as well as in the undammed Chachagua River. Sites above and below the dam had differences in their physicochemical variables, with wide variation and extreme values in variables measured below the dam in the San Lorenzo River. Sites below the dams had reduced water discharges, velocities, and depths when compared with sites above the dams, as well as higher temperatures and conductivity. Sites above dams were dominated by collector-gatherer-scrapers and habitat groups dominated by swimmer-clingers, while sites below dams had a more even representation of groups. In contrast, a comparison between two sites at different elevation in the undammed river maintained a similar assemblage composition. Tributaries might facilitate macroinvertebrate recovery above the turbine house, but the assemblage below the turbine house resembled the one below the dam. A massive sediment release event from the dam decreased the abundance per sample and macroinvertebrate taxa below the dam in the Peñas Blancas River. Our study illustrates the effects of hydropower production on neotropical rivers, highlighting the importance of using multiple measures of macroinvertebrate assemblage structure for assessing this type of environmental impact. Rev. Biol. Trop. 62 (Suppl. 2): 179-201. Epub 2014 April 01.

Existe poca información publicada sobre el efecto de grandes represas hidroeléctricas (>15m alto) en ríos tropicales. Investigamos los efectos de estas represas en las comunidades de macroinvertebrados acuáticos en dos ríos de Costa Rica. Medimos características físico-químicas y recolectamos macroinvertebrados a lo largo del año en dos ríos represados, Peñas Blancas y San Lorenzo, así como en el río Chachagua, el cual no era utilizado para la producción hidroeléctrica. Los sitios arriba y debajo de las represas presentaron diferencias físico-químicas, con amplia variación y valores extremos en las variables medidas debajo de la represa en el Río San Lorenzo. Los sitios arriba de las represas estaban dominados por colectores-recolectores-raspadores y nadadores-colgadores, mientras que debajo de las represas hubo una representación más equitativa de grupos funcionales. En contraste, las comunidades fueron semejantes en dos sitios a diferente elevación en el río sin represa. La presencia de afluentes podría haber facilitado la recuperación de macroinvertebrados arriba de la casa de máquinas, pero las comunidades fueron similares bajo la casa y abajo de la represa. Una liberación masiva de sedimentos disminuyó la abundancia y el número de táxones bajo la represa en el Río Peñas Blancas.

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We analyzed the effects of environmental factors on abundance, species richness, and functional group richness of Leptophlebiidae in 16 sampling points along four Cerrado streams. Across three periods of 2005, we collected 5,492 larvae from 14 species in stream bed substrate. These species belong to three functional feeding groups: scrapers, filtering collectors and shredders. The abundance and species richness were not affected by water quality, but habitat quality related to presence of riparian vegetation had positive effects on the abundance of shredders. Our results add important information on the natural history of the species and functional groups of aquatic insects and also provide relevant data for the monitoring and conservation of streams in the Brazilian Cerrado.

O efeito de fatores ambientais sobre a abundância, riqueza de espécies e grupos funcionais alimentares de Leptophlebiidae foi analisado em 16 locais pertencentes a quatro córregos de Cerrado, a partir de coletas de substrato em três períodos de 2005. Foram amostradas 5.492 larvas distribuídas em 14 espécies, classificadas em três grupos funcionais alimentares: raspadores, coletores-filtradores e fragmentadores. A abundância e riqueza de espécies não foram afetadas por nenhum dos fatores ambientais investigados, mas a integridade dos hábitats exerceu efeito positivo sobre a abundância dos fragmentadores, consequência da intrínseca interação desses organismos com a mata ciliar. Dessa forma, acreditamos que este trabalho agrega informações bioecológicas sobre as espécies e grupos funcionais de insetos aquáticos e poderá contribuir no monitoramento e conservação de riachos do Cerrado.

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The aim of this study was to describe the functional structure of the benthic community and how these patterns vary among the rainy and dry season. The study site is the Salvia stream, a second order tributary of Mundaú River, Rio LargoAL. This stream drains a fragment of Atlantic forest and does not have any direct anthropic activity. The macroinvertebrates were collected using a D net of 0,25mm mesh, during the rainy season (August) of 2010 and the dry season (March) of 2011. The macroinvertebrates were identified and classified as one of the following functional feeding groups: Shredders, Gathering Collectors, Filtering Collectors, Scrapers or Predators. The results showed a clear distinction among the two seasons, the rainy season, dominated by Shredders, and the dry season, dominated by the Gathering Collectors, suggesting a difference between the quality of the food available for the benthic community on the seasons. On the other hand, since both of the dominant functional groups are dependent on allocthonous organic matter, its shows that the stream is highly heterotrophic on both seasons. The study shows that the functional organization of the benthic macroinvertebrates in Salvia stream has clear seasonal patterns and also reinforces the importance of the season to biomonitorng studies for this region.

O objetivo deste estudo foi descrever a estrutura funcional da comunidade bentônica e como esses padrões variam entre a estação chuvosa e seca. A área de estudo foi o córrego Salvia, uma segunda ordem afluente do rio Mundaú, Rio Largo-AL. Este córrego drena um fragmento de Mata Atlântica e não tem qualquer atividade antrópica direta. Os macroinvertebrados foram coletados por meio de uma rede D de 0,25 mm de malha, durante o período chuvoso (agosto) de 2010 e na estação seca (março) de 2011. Os macroinvertebrados foram identificados e classificados em um dos seguintes grupos funcionais de alimentação: trituradores, coletores, coletores de filtragem, raspadores ou predadores. Os resultados mostraram uma clara distinção entre as duas estações, a estação chuvosa, dominado por trituradores, e a estação seca, dominada pelos coletores, sugerindo uma diferença entre a qualidade dos alimentos disponíveis para a comunidade bentônica nas estações. Por outro lado, uma vez que ambos os grupos funcionais dominantes são dependentes de matéria orgânica, mostrando que o córrego é altamente heterotrófico em ambas as estações. O estudo mostra que a organização funcional dos macroinvertebrados bentônicos no córrego Salvia tem padrões sazonais claros e também reforça a importância da temporada para estudos de biomonitoramento desta região.

Assuntos