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Aunque las cabeceras desempeñan un rol clave en las cuencas, se encuentran entre los hábitats más amenazados del planeta. Las cabeceras naturales no forestadas han sido poco investigadas en contraste con las forestadas. En consecuencia, el objetivo de este estudio fue analizar la estructura taxonómica y funcional del ensamble de insectos acuáticos en arroyos de cabecera en pastizales contrastando tres hábitats en dos periodos hidrológicos. La estructura funcional fue analizada considerando rasgos alimentarios y hábitos. Evaluamos el grado de solapamiento entre rabiones, pozas y parches de macrófitas; y las diferencias en métricas taxonómicas y funcionales entre estos hábitats fluviales. Los ensambles en macrófitas y en rabiones se solaparon parcialmente y se separaron del ensamble de las pozas. Los parches de macrófitas alojaron la mayor abundancia, pero la riqueza y la diversidad fueron mayores en los rabiones. La diversidad y la riqueza funcional presentaron el mismo patrón que el análisis taxonómico: fueron mayores en los rabiones, intermedias en las macrófitas y menores en las pozas. El análisis multivariado de grupos funcionales coincidió con el análisis taxonómico siendo los ensambles funcionalmente diferentes entre los hábitats. Los recolectores fueron predominantes, pero el análisis combinado de los rasgos alimentarios y los hábitos permitió distinguir el uso de los diferentes hábitats ya que los recolectores fueron principalmente agarradores en rabiones y reptadores en pozas y macrófitas. Las características del hábitat afectaron en consecuencia el hábito dominante dentro de los recolectores, con consecuencias potenciales sobre los procesos del ecosistema (e. g. tasas de procesamiento de la materia orgánica fina). Este estudio provee valiosa información sobre la estructura taxonómica y funcional de la comunidad de insectos acuáticos en cabeceras en pastizales que puede ser útil para el manejo y la conservación del recurso. Although headwater streams play a key role in drainage catchments, they are among the most threatened habitats on earth. Natural open-canopy headwaters, in particular, have received little research attention in contrast to the most worldwide studied forested catchments. Then, the aim of this study was to assess the taxonomic and functional structure of insect assemblages in grassland headwaters contrasting three different habitats in two hydrological periods. Functional composition was quantified considering trophic and habit traits. We assessed the degree of assemblage overlapping among three habitat units (riffles, pools and macrophyte patches) and the differences in taxonomic and functional metrics among these stream habitats. Assemblages in macrophytes and riffles were rather overlapped and separated from the assemblage in pools. Macrophyte patches held the greatest insect abundance but richness and diversity were higher in riffles. Functional richness and diversity followed the same pattern found for the taxonomic analysis: higher in riffles, intermediate in macrophytes and lower in pools. The multivariate approach performed with functional groups concurred with the taxonomic analysis, being assemblages functionally different among habitats. Assemblages were dominated by gathering collectors, but the combined analysis of trophic and habit traits allowed disentangling the use of different habitats since collectors were mainly clingers in riffles and sprawlers in pools and macrophyte patches. Habitat characteristics affected the dominant habit within gathering collectors, with potential consequences for ecosystem processes (e.g. processing rates of fine organic material). This study provides valuable information on the taxonomic and functional structure of the insect community in grassland headwaters that can be useful for stream manage-ment and conservation. Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Rodríguez, María Pía. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Geología; Argentina Fil: Cibils Martina, Luciana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Albariño, Ricardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiología; Argentina Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina

Nineteen geographical records for species of Odonata in 2 provinces of Argentina are documented. We provided records for 9 newly recorded species for Córdoba: Lestes spatula Fraser, 1946, Andinagrion peterseni (Ris, 1908), Argentagrion ambiguum (Ris, 1904), Erythemis attala (Selys in Sagra, 1857), Erythemis plebeja (Burmeister, 1839), Erythrodiplax media Borror, 1942, Micrathyria longifasciata Calvert, 1909, Micrathyria hypodidyma Calvert, 1906, and Tramea cophysa Hagen, 1867. In San Luis, we provided records for 10 newly recorded species: Hetaerina rosea Selys, 1853, Acanthagrion lancea Selys, 1876, Ischnura fluviatilis Selys, 1876, Oxyagrion rubidium (Rambur, 1842), Castoraeschna decurvata Dunkle & Cook, 1984, Rhionaeschna pallipes (Fraser, 1947), Phyllocycla argentina (Hagenin Selys, 1878), Erythrodiplax corallina (Brauer, 1865), Perithemis mooma Kirby, 1889, and Planiplax erythropyga (Karsch, 1891). Among these records, we extend the geographic distribution of A. peterseni and R. pallipes, which areendemic to Argentina and recorded P. erythropyga for the first time in Chaco phytogeographic province Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto; Argentina. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente.; Argentina Fil: Berejnoi, Diego E.. Universidad Nacional de Río Cuarto; Argentina Fil: Rodríguez, José S.. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentina Fil: Bedano, José Camilo. Universidad Nacional de Río Cuarto; Argentina. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente.; Argentina Fil: Molineri, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentina

The need for tree-derived industrial products is causing an increase in the land surface covered by fast-growing monoculture plantations throughout the world. Species planted are selected mostly prioritizing their rapid growth, with less consideration to minimizing the negative environmental effects they create. Among the various ecosystems that can be negatively affected by plantations, streams are among the most impacted, as they strongly depend on dead organic matter from the surrounding vegetation. Changes in land use in favour of monocultures can have large consequences on stream biodiversity and functioning since they can lead to alterations in the diversity, quantity, quality and timing of litter inputs. Here, we review the literature dealing with the effects of plantations on litter decomposition in streams, with special focus on eucalyptus and conifer plantations, which have been more thoroughly studied than other planted tree species. The effects of plantations on litter decomposition in streams have a degree of regional specificity, and depend on the composition of detritivores, litter characteristics (of native and exotic species) and local environmental conditions. There is, nonetheless, a need for further research describing the effects of specific planted exotic species and for more studies out of Europe and North America.

Traditionally, South American aquatic insects have been divided into cold and warm adapted forms. Cold-adapted forms inhabit freshwater systems from higher latitudes, or higher altitudes even around the Equator. Warm-adapted groups are defined as those found in lower latitudes and altitudes. This work aims to answer the questions: Are mayfly assemblages geographically segregated according to geographical (latitude) and topographical (altitude) surrogates of temperature? If so, where is this transition located? Location: South America. Methods: We compiled a data set about the relative incidence of 52 mayfly genera in 326 sampled communities. They span from 0 to 4,320 m and from 47.77° S to 5.74° N latitude. By virtue of the compositional nature of the data set, we applied the statistical procedures behind the Aitchison compositional data analysis. We delimited groups of assemblages based on their Aitchison distances and projected the data points onto a biplot obtained through Principal Component Analysis adjusted to compositions (Aitchison PCA). Results: A strong correspondence among biological and geographical information was detected, with mayfly assemblages clearly segregated in space. Andesiops and Meridialaris are typical cold-adapted forms; Baetodes, Leptohyphes and Thraulodes represent the warm group. Thermal groups can be separated by a curved line of altitude in function of latitude expressed in terms of a superellipse arc. Main conclusions: The classical ecological bipartition of mayflies into warm and cold freshwater groups is formalized quantitatively. The dividing line between warm and cold assemblages levels off at high altitudes (c. 3,300 m) around the Equator and falls to sea level at southern latitudes. The community bipartition line is useful for tracking global change through records of altitudinal displacement below and above of the warm/cold line of involved ecological groups. Fil: Dos Santos, Daniel A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentina Fil: Molineri, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentina Fil: Nieto Peñalver, María Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentina Fil: Zúñiga, María Angélica. Universidad del Valle; Colombia Fil: Emmerich, Daniel Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentina Fil: Fierro, Pablo. Universidad de Concepción; Chile Fil: Pessacq, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagóica. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Centro de Investigación Esquel de Montaña y Estepa Patagónica; Argentina. Centro de Investigaciones Esquel de Montaña y Estepa Patagónicas (ciemep) Esquel; Argentina Fil: Rios-Touma, Blanca. Universidad de Las Americas; Ecuador Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Gomez, Graciela Cecilia. Universidad Nacional de Jujuy. Instituto de Biología de la Altura; Argentina. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina Fil: Salles, Frederico F.. Universidade Federal do Espírito Santo; Brasil Fil: Encalada, Andrea C.. Universidad San Francisco de Quito; Ecuador Fil: Principe, Romina Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina Fil: Gomez, Graciela Cecilia. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Jujuy. Universidad Nacional de Jujuy. Centro de Investigaciones y Transferencia de Jujuy; Argentina Fil: Valdovinos Zarges, Claudio. Department Of Aquatic Systems, Faculty Of Environmental; Chile Fil: Dominguez, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; Argentina

Las macrofitas cumplen un rol importante en los sistemas loticos, incrementando la heterogeneidad del habitat, proveyendo alimento y refugio para la fauna. El objetivo del estudio fue analizar la estructura y composicion de la comunidad de macroinvertebrados asociados a macrofitas en arroyos de cabecera en pastizales de altura (subcuenca Ctalamochita, Cordoba, Argentina) en 2 periodos hidrologicos. Asimismo, se evaluo la estructura de los ensambles de macroinvertebrados presentes en diferentes especies de macrofitas ( Hydrocotyle spp., Rorippa nasturtium-aquaticum y Ranunculus flagelliformis ). Se muestrearon 3 arroyos durante los periodos hidrologicos de aguas altas (marzo de 2012) y aguas bajas (agosto de 2012). En cada periodo se colectaron muestras de macroinvertebrados asociados a la macrofita dominante en cada arroyo. Se identificaron 72 taxones de macroinvertebrados fitofilos. Los mas frecuentes y abundantes fueron Naidinae, Hyallela curvispina, Americabaetis spp., Corynoneura spp. y Rheotanytarsus spp. La composicion de los ensambles difirio entre periodos hidrologicos y se detecto una mayor abundancia de macroinvertebrados en R. nasturtium-acuaticum . Los resultados demuestran que los parches de macrofitas en los arroyos de cabecera en pastizales de altura albergan una fauna de macroinvertebrados abundante y diversa, y proporcionan a su vez importante informacion de base para el biomonitoreo de estos sistemas acuaticos.

The assessment of biotic-habitat relationships provides key information to predict biotic responses to perturbations and important tools for river management and monitoring. This study aimed to assess the spatial distribution of Ephemeroptera and Trichoptera in mountain streams of central Argentina. We evaluated the effect of seasonality and identified the variables conditioning the abundance of the assemblages and the habitat with the highest taxonomic richness. Sampling was carried out in four streams (Carcarañá River basin) during high and low water periods. Three lotic habitats were sampled: riffles, coarse substrate runs, and fine substrate runs; and physicochemical and habitat variables were measured. We found differences in assemblage composition, among the 25 genera of Ephemeroptera and Trichoptera, at the habitat level. The most important variables affecting distribution patterns were substrate and flow type, but macroalgae and organic matter (twigs, leaves, and detritus) were also important predictors. Riffles maintained the highest richness but when considering only the Ephemeroptera taxa, fine substrate runs emerged also as an important habitat for these taxa. Our study provided valuable ecological information related to habitat preference of taxa with a key role in stream functioning and of great usefulness for the monitoring of lotic systems. Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina Fil: Cibils Martina, Luciana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina

Las charcas temporarias constituyen “puntos calientes” de biodiversidad dentro de una región o paisaje. Dada su importancia en el contexto paisajístico, el objetivo de este estudio fue evaluar la diversidad y composición del ensamble de macroinvertebrados acuáticos de una charca temporaria urbana, analizando su distribución espacial y temporal. Se recolectaron macroinvertebrados acuáticos en diferentes hábitats dentro de la charca durante período seco y húmedo, se identificaron y cuantificaron en el laboratorio y se asignaron a grupos en función de sus estrategias de vida. Se registraron 53 taxa de macroinvertebrados y el análisis de correspondencias diferenció el ensamble en función de la presencia de vegetación acuática y de la estacionalidad. Mediante el método del Valor Indicador se identificaron taxa característicos de los distintos hábitats y períodos hidrológicos. El Grupo 1 de estrategia de vida (sobreviven a la desecación, requieren agua para la reproducción y tienen dispersión pasiva) y el Grupo 4 (no sobreviven a la desecación, requieren agua para la reproducción y tienen dispersión activa) presentaron mayor número de taxa en todos los hábitats. La mayor abundancia se registró en los sedimentos sin vegetación mientras que la riqueza, la diversidad y la equitatividad fueron mayores en hábitats vegetados. Los resultados destacan la importancia de las macrófitas y la estacionalidad en el mantenimiento de la biodiversidad y proporcionan importante información de base para el monitoreo, manejo y conservación de charcas temporarias urbanas., Temporary ponds are worldwide recognized as ‘hotspots’ of biodiversity within a region or landscape. The aim of this study was to assess the diversity and composition of the aquatic macroinvertebrate assemblages of an urban temporary pond, due to its importance in the landscape context. We analized the spatial distribution of the assemblages in different habitats and their temporal variation. Aquatic macroinvertebrates were collected in wet and dry periods by sampling scoops and hand net. The specimens were identified, quantified, and assigned to groups considering their life-history strategies. Fifty-three invertebrate taxa were identified and the correspondence analysis distinguished the assemblages in relation to the presence of aquatic vegetation and seasonality. The Indicator Value method identified characteristic taxa of the different habitats and hydrological periods. The Group 1 of life-history strategy (with adaptations to desiccation, water requirement for reproduction and with passive dispersion) and the Group 4 (without adaptations to desiccation, water requirement for reproduction and with active dispersion) presented the highest number of taxa in all habitats. The highest abundance was observed in sediments without vegetation whereas richness, diversity and evenness were higher in vegetated habitats. These results highlight the importance of macrophytes and seasonality in the maintenance of biodiversity and provide baseline information for monitoring, management and conservation of urban temporary ponds., Instituto de Limnología "Dr. Raúl A. Ringuelet"

La taxonomía de Chironomidae se apoya fuertemente en la integración de las características morfológicas de todas las fases del ciclode vida, las cuales se pueden obtener mediante la cría en laboratorio. Este estudio desarrolló un método de cría en laboratorio delarvas de Chironomidae de ambientes lóticos. El método consta de una circulación constante de agua y distintos ítems alimenticios.Esta metodología ha permitido obtener asociaciones de los estados de larva, pupa y adulto para la identificación de especiespresentes en una región de Argentina en la que el estado de conocimiento de la familia Chironomidae es incipiente., The taxonomy of Chironomidae is strongly supported by the integration of morphological characteristics of all stages of the life cycle, which can be obtained through laboratory rearing. This study was developed in laboratory to test rearing method for lotic Chironomidae larvae. The method included constant water circulation and different food items. This methodology allowed obtaining associations of larva, pupa and adult stages for the identification of species from an Argentinean region in which the knowledge of Chironomidae family is incipient., Instituto de Limnología "Dr. Raúl A. Ringuelet"

Our aim was to analyze the combined effect of grazing and light on composition, structure, functional diversity (FD) and succession of algal communities in two headwater streams (grassland and pine afforested). We hypothesized that algal communities in the grassland stream are top-down controlled, as a result of higher grazing; meanwhile, in the afforested stream, algal communities are bottom-up shaped, mainly due to sunlight reduction. In in situ experiments, we used platforms to avoid grazing in both streams, and the substrates were extracted at 23, 45 and 73 days. Algal community composition was different between stream types. Seventy percent of structural and biomass variables responded to grazing. In the grassland stream, grazing reduced richness and ash-free dry mass (AFDM), especially after 45 days, while in the afforested stream, at the same time, grazed substrates showed higher richness and AFDM than ungrazed substrates. Net grazing effect was higher on algal biomass of grassland streams. Then, 30% of functional traits showed grazing effect. High profile algae predominated in the grassland stream, where ungrazed substrates showed higher proportions of species with pad mucilage and colonial life form. Algal communities in the afforested stream remained at an early stage of succession, with a predominance of small and low profile algae in both substrates, and FD and evenness indices were lower. Our results indicate that the relative strength of top-down versus bottom-up control is different among stream types and the primary regulatory factor of freshwater communities can be modified according to such forestry practice. Fil: Cibils Martina, Luciana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Gari, Elena Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Albariño, Ricardo Javier. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina

Lotic ecosystems are highly affected by land use changes such as afforestation of natural areas for management or commercial purposes. The aim of this study was to analyze the effect of pine plantations on benthic invertebrate communities in mountain grassland streams. Additionally, we assessed if thehydrological period modifies the effect of afforestation on stream invertebrates. Three headwater streams draining grasslands (reference streams) and three draining plantations of Pinus elliottii were selected ina mountain watershed of Córdoba province (Argentina). Hydrologic and physicochemical variables were registered and benthic invertebrate samples were collected in each stream at two different hydrologicalperiods. Total invertebrate abundance, richness and diversity were reduced in afforested streams as well as the number of indicator taxa. In addition, invertebrate functional structure (i.e. taxonomic richness and total and relative abundance of functional feeding groups, FFG) showed differences between streams with different riparian vegetation and between hydrological periods. Total abundance of all FFGs was lower in afforested streams and scrapers? relative abundance was higher in grassland streams at the lowwater period. In addition, in most FFGs richness was diminished in afforested streams. Changes in light intensity, hydrology and coarse organic matter inputs produced by afforestation alter fluvial habitats andconsequently the composition and trophic structure of invertebrate communities in grassland streams of Córdoba mountains. Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cibils Martina, Luciana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Albariño, Ricardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiologia; Argentina

We evaluated changes in benthic algal community in grassland mountain streams converted to exotic pine afforestation. Three headwater streams draining grasslands and three draining plantations of Pinus elliottii were selected in a semiarid mountain watershed (Córdoba, Argentina). Hydraulic and physicochemical variables were recorded and benthic algal samples were collected in each stream at two hydrological periods (high and low flow). Light intensity was lower in afforested streams. Community composition differed between grassland and afforested streams. Algal abundance and richness, richness of chlorophytes and cyanobacteria, and the indicator taxa were reduced in afforested streams. Diversity, evenness and biomass were higher in the high water period but did not differ between riparian vegetation types. The observed changes in benthic algal attributes may have implications in ecosystem functioning because of the central role that algal biofilms play in the productivity of these fluvial systems, as sources of food, energy and oxygen. Fil: Cibils Martina, Luciana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Principe, Romina Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Gari, Elena Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Albariño, Ricardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

We evaluated changes in the succession process in benthic algal communities of an afforested stream by comparing them with those in a grassland stream through analysis of temporal changes in composition, structure and functional traits in a 3-month experiment. We hypothesized that sunlight intensity reduction as a result of streamside implanted tree shading reduces the succession rate and community physiognomic complexity. We selected two streams with different riparian cover (grassland and pine afforestation) for installation of unglazed tiles as artificial substrates. The tiles were collected from each stream after 23, 45 and 73 days of exposure. Afforestation produced changes in algal succession, with lower biomass, lower diversity at the beginning of the experiment, and an increase in the proportion of small, low-profile, tolerant, unicellular and stalked algae, coinciding with the predominance of Achnanthidium. However, the grassland stream contained a higher proportion of intermediate-size algae, as well as a larger proportion of high-profile algae, coinciding with the expected results. In the afforested stream, succession proceeded toward the dominance of low-profile species, that were tolerant of low-light conditions. However, in grassland streams with higher sunlight availability, high-profile algae prevailed without the displacement of tolerant forms. Overall, our results indicate that algal communities in afforested stream remain structurally simpler. Fil: Cibils Martina, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto; Argentina Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Márquez, Javier Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto; Argentina Fil: Gari, Elena Noemi. Universidad Nacional de Río Cuarto; Argentina Fil: Albariño, Ricardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Small streams are ruled by the influence that riparian vegetation has on food webs since it regulates the entry of organic matter and sunlight. The plantation of perennial tree species along banks of grassland streams results in heavy shading of stream bottoms and large inputs of coarse organic matter. In this study, we experimentally analyzed the taxonomic and trophic structure of invertebrate assemblages colonizing pine needles and plastic filaments (mimicking the physical structure of needle accumulations) placed in one afforested and one natural grassland stream from the mountainous region of central Argentina. We studied these two experimental substrates to infer if pine leaves were colonized by invertebrates as food resource or only as a substratum for support and refuge. Coarse mesh litter bags were used to simulate large litter accumulations and four bags of each treatment were randomly removed after 46, 89, and 158 days of exposure. Our study showed that taxonomic and trophic composition of invertebrate assemblages colonizing needles and plastic filaments were mostly similar suggesting that needles constitute mainly a stable habitat but not a trophic subsidy. Richness, diversity, and evenness were lower in assemblages of the afforested stream and differences in taxonomic and trophic structure were also found between afforested and natural grassland streams. We conclude that environmental changes associated to afforestation modified invertebrate assemblages colonizing litter but in the same way for needles and plastic filaments since no evidence was found for supporting that the organic nature of needles makes this substrate different from plastic filaments for invertebrates. Therefore, needles would not be being used as a food resource. Our study highlights the importance of preserving riparian zones mostly unaltered to maintain natural aquatic communities when implementing afforestation programes in grassland landscapes. Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Principe, Romina Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Cibils Martina, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Albariño, Ricardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

We assessed the effect of small dams on stream habitats and on the structure and function of benthic macroinvertebrate communities in mountain streams of Cordoba, Argentina. Two streams with small dams (impacted streams) and two streams without dams (control streams) from the Carcarana River upper sub-basin were selected. Dominant hydraulic units were identified and benthic samples were collected in each of these units during high and low water periods. According to this study small dams may have impact on the function and structure of the invertebrate community, though hydraulic habitats would not be affected. Fourteen hydraulic units were found and changes due to dams were not observed as assessed by the detrended correspondence analysis. The canonical correspondence analysis grouped samples mainly in relation to hydraulic habitats whereas TWINSPAN grouped samples according to the presence of dams. Nested ANOVAs showed changes in richness and diversity, in the abundance of filterers and shredders and in the abundance of certain species. Small dams generate quite small reservoirs and their permeability may be greater than those of large dams. The behaviour of macroinvertebrate populations in drift and colonization processes, the continuity of the riparian structure and the discharge of planktonic algae downstream the dams may be some factors determining the ecological changes produced by small impoundments.

The benthic community of a braided reach of a lowland river was studied with the aim to identify functional habitats through the assessment of potential habitats. Functional habitats were defined considering physical and biological characteristics. Three reaches of the Chocancharava River (Cordoba, Argentina) were selected and six potential habitats were sampled during high and low water periods. Hydraulic and environmental variables were also registered in each sampling occasion. Taxonomic composition, macroinvertebrate abundance, richness, diversity and evenness were estimated for each identified functional habitat. TWINSPAN analysis was applied separately for two data sets (high water and low water period). This analysis showed that samples of the low water period were mainly grouped in relation to three habitats units: vegetated habitats, unvegetated habitats and habitats related to bars. These three habitats were considered functional habitats. The whole biological and environmental data sets were ordinated by Canonical Correspondence Analysis (CCA) showing a significant relationship between benthic assemblages and environmental variables. This analysis grouped samples in relation to the functional habitats identified by TWINSPAN and indicated that the most influential environmental variables explaining the ordination were: current velocity, depth, substrate size and cover percent of rooted emergent macrophytes. Faunal composition determined by CCA for each functional habitat was in agreement with the results obtained by the Relative Preference Index (RPI). Factorial ANOVAs showed that abundance, taxonomic richness, diversity and evenness were different among the functional habitats and that the community attributes were influenced by the effect of the hydrological period and habitat. As the functional habitat approach provides useful tools in management and river rehabilitation the use of this methodology may allow to develop more appropriate restoration strategies to be applied in altered lowland reaches.

Structure of benthic Chironomidae assemblages and their spatial-temporal dynamic were analyzed in upland and lowland habitats from the Chocancharava River basin (Cordoba, Argentina). Sampling was performed in three tributary streams and in three lowland reaches of the river during high and low rainfall periods. Characteristic taxa of upland and lowland reaches and of the different habitats in these reaches were identified using the IndVal method. Chironomidae assemblages were different between upland and lowland reaches and among habitats in each reach, as assessed by Multiresponse Permutation Procedure and Canonical Correspondence Analyses. Substrate type and current velocity were the major explanatory variables structuring the assemblages in upland reaches whereas in lowland reaches current velocity and aquatic vegetation were the most important variables. The highest richness was found in the most complex habitat units in both upland and lowland stretches as assessed by Analyses of Variance. Chironomidae larvae responded to longitudinal changes of hydraulic variables and to local variations of fluvial habitats at different reaches. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In the past decades, afforestation of grassland landscapes has gained importance both as an economic activity and a mechanism to mitigate anthropogenic carbon emissions. This study evaluates the effect of pine afforestation on grassland streams analyzing changes in two integrative ecological indicators: leaf litter breakdown and primary production. We compare those results with changes in structural attributes of benthic biota (primary producers and invertebrates). Six contiguous first-order streams were selected in the upper basin of the Ctalamochita river (Córdoba, Argentina): three reference streams draining grasslands and three streams draining Pinus elliottii afforestations. Two in situ experiments were performed to compare leaf litter breakdown and primary production between grassland and afforested streams. Additionally, invertebrate assemblages in leaf litter and riffles, and periphyton standing stock were sampled and assessed. Nine out of 26 structural indicators showed differences between stream types but indicators measuring changes at the basal level of the food web (i.e. detritus and primary producers) were less sensitive than those recording changes in consumers. Our attempt to measure direction and magnitude of changes on stream functioning following afforestation was halted by our simple implemented methodology (i.e. leaf pack method for leaf litter decay and biofilm accrual on natural stone substrates for primary production assessments); only 1 out of 4 indicators differed. We argue that the lack of strong differences in elemental measurements of primary production and needle decay between afforested and grassland streams resulted from compensating opposing forces controlling such processes, i.e. higher grazing vs. higher sunlight in grassland streams and higher shredding vs. lower microbial decomposition mediated by lower temperature in afforested streams. Attributes related to the invertebrate compartment showed the highest sensitivity to afforestation, emphasizing their value as biological indicators of stream ecological integrity. Fil: Principe, Romina Elizabeth. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquimicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Márquez, Javier Andrés. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquimicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cibils Martina, Luciana. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquimicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; Argentina Fil: Albariño, Ricardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiologia; Argentina

Pine afforestation of grassland streamsmay lead to changes in species traits and thereforefunctional diversity of epilithic algal community.Here, we studied trait-based responses in three grasslandand three afforested streams in a mountainwatershed of Co´rdoba, Argentina. We hypothesizedthat afforestation would reduce functional diversitythrough a simplification of periphyton architectureresulting from reduction in light availability, and thatchanges in hydrological periods would influencecommunity responses. Algal samples were collectedat each stream during two different hydrologicalperiods (high flow and low flow), and physicochemicalvariables were recorded. Selected traits includedstrategies and morphological characters related toresource access and disturbance resistance (size,morphological guild, resource requirement, attachmentmechanism and life-form). We calculated twoindices of functional diversity: Rao?s quadraticentropy (FDQ) and functional variance. Most traitcategories showed a significant effect of one or bothfactors; 26 % discriminated between vegetation types,26 % reflect the changes between hydrological periods,and 47 % were sensitive to both of them. Ourresults revealed some categories of traits that can beused to distinguish changes in riparian vegetation,such as unicellular life-form and high-profile guild.Functional diversity of single traits was affecteddifferently by pine afforestation. However, the mostintegrative index, the FDQ mean, partially supportedour hypotheses. Afforestation reduced FDQ mean by50 %, but only during low-flow period. FDQ mean washigh and similar between streams at high flow, whenenvironmental factors, such as discharge and temperature,could prevail on differences in riparianvegetation. Fil: Cibils Martina, Luciana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gari, Noemí. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Albariño, Ricardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina

Chironomidae es una de las familias más abundantes y diversas en los ecosistemas de agua dulce, sin embargo su complejidad sistemática ha sido motivo de su escaso desarrollo en muchos estudios limnológicos. El objetivo de este estudio fue analizar los ensambles de Chironomidae bentónicos y derivantes de un arroyo serrano de la región central de Argentina evaluando abundancia, diversidad y composición de especies en diferentes hábitats fluviales y distintas estaciones del año. Se tomaron muestras cuantitativas de bentos y deriva en el arroyo Achiras (Córdoba, Argentina) en hábitats de rabión y corredera, y se registraron variables ambientales en las cuatro estaciones del año, entre 2007 y 2008. Se registró un total de 25 taxones pertenecientes a cuatro subfamilias. Los quironómidos bentónicos constituyeron el 19% de la comunidad de macroinvertebrados, mientras que en deriva representaron el 33%. En el bentos dominó Thienemannimyia sp. y en la deriva, Corynoneura sp. De acuerdo con los resultados de ANOVAs de dos vías, los mayores valores de riqueza taxonómica y densidad bentónica se registraron en el periodo de aguas bajas (otoño e invierno) y la diversidad de quirónomidos bentónicos fue mayor en rabión. Por el contrario, para el ensamble de derivantes sólo la equitatividad fue diferente entre hábitats y entre estaciones. El análisis TWINSPAN mostró una separación espacio-temporal de las muestras de bentos, mientras que las muestras de deriva se segregaron sólo temporalmente lo que sugiere que el transporte aguas abajo de los invertebrados homogeniza la variación espacial observada en el bentos. La densidad de bentos y deriva varió de manera similar a través de las estaciones del año y el coeficiente de Jaccard presentó un alto índice de similitud entre bentos y deriva (86%). Este trabajo posibilitó conocer la dinámica temporal y espacial de los quironómidos bentónicos y derivantes en un arroyo serrano. La ampliación del conocimiento taxonómico, biológico y ecológico de Chironomidae posibilitará adecuar e implementar estrategias de manejo y conservación de los ecosistemas lóticos en la región central de Argentina. Spatio-temporal variation of benthic and drifting Chironomidae (Diptera) in a mountain stream in Córdoba, Argentina. Chironomidae is one of the most abundant and diverse families in freshwater ecosystems, however its highly complex systematic has led to its scarce development in many limnological studies. The aim of this study was to analyze benthic and drifting Chironomidae assemblages in a mountain stream of central Argentina assessing abundance, diversity and taxa composition in different fluvial habitats and seasons. Quantitative benthic and drift samples were taken in the Achiras stream (Córdoba, Argentina) in rifles and runs, and environmental variables were measured in each season between 2007 and 2008. A total of 25 taxa were registered belonging to four subfamilies. Benthic chironomids represented 19% of the macroinvertebrate community, whereas they constituted 33% in drift. Thienemannimyia sp. dominated in benthos and Corynoneura sp. in drift. According to the two-way ANOVAs results, the highest taxonomic richness and benthic density were registered during the low flow period (autumn and winter) and the highest benthic diversity was found in riffles. On the contrary, in the drifting assemblage only evenness was different between habitats and among seasons. TWINSPAN analysis showed a spatio-temporal segregation of benthic samples, whereas drift samples were separated only temporally suggesting that the dislodgment of invertebrates downstream homogenize the spatial variation observed in benthos. Benthic and drift density varied in a similar manner through seasons and Jaccard coefficient showed a high similarity index between benthos and drift (86%). This study allowed knowing the spatio-temporal dynamic of benthic and drifting Chironomidae in a mountain stream. The increase of knowledge in relation to taxonomy, biology and ecology of Chironomidae will allow to adequate and apply management and conservation strategies of lotic ecosystems in the central region of Argentina. Fil: Zanotto Arpellino, Juan Pablo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Oberto, Ana M.. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Gualdoni, Cristina M.. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina

Aquatic macroinvertebrates living in anastomosing lowland rivers use different habitats and respond differently to the hydrological regime. In this paper, the structure and composition of benthic, drifting and marginal macroinvertebrate assemblages are analyzed in the lowland river Ctalamochita (Cordoba, Argentina). The assemblages were studied in an annual cycle; a comparison among the composition of benthos, drift and marginal fauna was carried out; and size structure of the assemblages was characterized. Samples were obtained from two sites: a rural and an urban site. In total 73 taxa of aquatic macroinvertebrates were collected. Benthos was characterized by Chironomidae and Oligochaeta; marginal fauna was mainly constituted by Coleoptera, Heteroptera, Decapoda, the Trichoptera Nectopsyche sp., Ephemeroptera and Odonata. Drifting assemblage was composed by macroinvertebrates from local and remote upstream benthos, and from the marginal zone. Marginal fauna diversity was higher than benthos and drift. Total biomass of the assemblages pooled together was relatively equitably among size classes. Larger size classes consisted of organisms from the marginal zone whereas the smallest ones were composed by benthic and drifting organisms. In the study area there is habitat partitioning in the lateral dimension of the river. Marginal fauna was more diverse due to the asymmetry of transport and deposit processes, which generate a heterogeneous habitat in the bankside. The relation between fine substrate and high current velocity determines an unstable habitat in the central channel, which makes colonization by benthic macroinvertebrates difficult.

Drastic changes in the composition and physiognomy of riparian vegetation, such as the conversion of grassland to forest, are expected to alter interactions among light availability, primary producers and herbivores. Our aim was to examine in laboratory the influence of a ubiquitous grazer on periphyton grown in a grassland unshaded stream (reference) vs. periphyton from a nearby pine afforested stream. Besides, we evaluated how the community responds to the removal of grazing. Given that grassland streams are exposed to higher light intensity and grazers are more abundant compared to afforested streams, we proposed thatif biofilm grown in the afforested stream are dominated by grazing-vulnerable algal species, grazing pressure by Helicopsyche sp. should be stronger. In addition, if biofilm from the afforested stream has low quality or is less abundant as food for consumers, the effects of Helicopsyche sp. may be stronger or weaker depending on their feeding decisions. Helicopsyche sp. caused a decrease in richness and diversity in periphyton grown in the grassland stream and its net grazing effect on chlorophyll a (Chl a) was higher. Algal community composition from grassland stream was strongly changed after grazing, with a decrease in the proportion of overstory algae. In contrast, algal community structure of periphyton from the afforested stream was neither affected by grazing nor by grazing exclusion. Helicopsyche sp. produced significant changes in a short time in structural attributes of algal communities, mainly in periphyton from the grassland stream suggesting that herbivory, as a functional factor, is diminished following afforestation. Fil: Cibils Martina, Luciana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Márquez, Javier Andrés. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gari, Elena Noemí. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina Fil: Albariño, Ricardo Javier. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina

In this study we evaluated the effect of a dam on epilithic algal communities by analyzing community response after dam construction and by comparing community composition, structure and biomass upstream and downstream of the dam. Samples of epilithic algae and environmental data were collected at each site during high and low water periods before and after dam construction in Achiras Stream (Córdoba, Argentina). Ordinations showed modifications in algal assemblages after dam construction and downstream of the dam. Ordinations also suggested a loss of seasonality at the downstream site since the assemblages were similar between hydrological periods after dam construction. Our results also pointed out that dam construction affected not only the assemblages living at downstream site but also those in the upstream site. Indicator species, obtained by the Indicator Value method, showed that, after dam construction, there could have been an increase in nutrient concentration and a release of plankton from the impoundment. Abundance, richness and diversity were altered after dam construction as assessed by ANOVAs derived from a modified BACI Design. The proportion of earlysuccessional species was higher at the upstream site while late-successional species were dominant at the downstream site, as predicted. Current velocity was higher in the high water period upstream of the dam, with no differences between hydrological periods at the downstream site. So, lower fluctuations in discharge downstream of the dam may have helped succession advance, whereas at the upstream site, mainly during the high water period, floods appear to have caused sloughing of life forms from the outer layers of the biofilm, resetting the algal community to early successional stages. It may be concluded that the dam affected algal community and favored succession advance mainly by reducing current velocity and flow fluctuations. Fil: Cibils Martina, Luciana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba; Argentina; Fil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba; Argentina; Fil: Gari, Elena Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba; Argentina