Disentangling grazing and light controls on algal communities in grassland and afforested streams

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; ArgentinaFil: 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; ArgentinaFil: Gari, Elena Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; ArgentinaFil: 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; ArgentinaFil: 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; Argentin

Diet of tadpoles of Physalaemus biligonigerus (Leiuperidae) from agricultural ponds in the central region of Argentina

The intensification of agriculture has led an important loss of natural habitats, with significant consequences for biodiversity. In this sense, the studies on anuran amphibian tadpoles inhabiting these environments are relevant, because the larval stage is a phase of population regulation. The aim of this study was to analyze the diet in Physalaemus biligonigerus tadpoles, an anuran species widely distributed in South America and that inhabit agroecosystems. Three sites were sampled; two agroecosystems with different alteration degrees (AG1 and AG2) and an uncultured (SM) third place. The captured tadpoles were anesthetized, fixed and preserved in formaldehyde (10%). Subsequently, the complete intestine was removed and analyzed for food items under a binocular microscope. The diet in P. biligonigerus tadpoles has a dominance of algae Bacillariophyceae, mainly in agroecosystems, due to the presence of the genera Navicula, Nitzschia and Gomphonema. There was a considerable abundance of the Gomphonema genus in the AG2 site. In addition, in the AG1 site several non-diatom algae were particularly abundant in the diet, such as the genera Euglena, Oedogonium and Chaetophora. In the SM site, the non-diatom genus Oscillatoria was well represented in the diet. Tadpoles inhabiting the site with abundant crop and livestock (AG1) ingested a significantly smaller amount of food. The presence of certain algae associated with eutrophic environments could indicate some pollution in agroecosystems (AG1 and AG2). Larval diet is suggested as a potential bioindicator of environmental health for these areas

Trophic ecology in tadpoles of Rhinella arenarum (Anura: Bufonidae) in agroecosystems and their possible implications for conservation

The progress of the agriculture border has led an important loss of natural habitats, with significant consequences for biodiversity. In this sense, the studies in anuran amphibian tadpoles inhabiting these environments are relevant, because the larval stage is a phase of population regulation. The aim of this study was to analyze the body condition and diet in Rhinella arenarum, tadpoles, an anuran species widely distributed in South America and that inhabit agroecosystems. Three sites were sampled, two agroecosystems with different alteration degrees (C1 and C2) and an uncultured (SM) third place. The captured tadpoles were anesthetized, fixed and preserved in formaldehyde (10%). Subsequently, body measurements were made and the complete intestine was removed and analyzed for food items under a binocular microscope. The diet in R. arenarum tadpoles has a dominance of algae Bacillariophyceae, followed by Cyanophyceae. In particular, the class Bacillariophyceae, due to the presence of the genus Navicula, Nitzschia, Gomphonema and Hantzschia, was important in the diet of the anurans in those agroecosystems. Class Cyanophyceae, mainly represented by genus Oscillatoria and Euglenophyceae represented by Euglena and Strombomonas, were predominant in the diet of the anurans in SM. Some differences in the total items consumed by tadpole were observed between the studied sites. Tadpoles that inhabit the modified sites (C1 and C2) recorded a significantly smaller amount of food. Moreover, the tadpoles that inhabit these sites showed a lower body condition. The presence of certain algae associated with eutrophic environments, could indicate some pollution in agroecosystems (C1 and C2). Food resources would be lesser in places with strong agricultural activity, possibly with a greater degree of eutrophication. A smaller food amount could have consequences at population level for the short and long time terms, because of its impact on individual growth. Larval diet is suggested as a potential bioindicator of environmental health for these areas.Fil: Bionda, Clarisa de Lourdes. 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; ArgentinaFil: Gari, Elena Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; ArgentinaFil: Luque, María Elisa. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; ArgentinaFil: Salas, Nancy Edith. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; ArgentinaFil: Lajmanovich, Rafael Carlos. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Martino, Adolfo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentin

Effect of a dam on epilithic algal communities of a mountain stream: before-after dam construction comparison

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; ArgentinaFil: 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; ArgentinaFil: 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; Argentin

Ecología trófica en larvas de Rhinella arenarum (Anura: Bufonidae) en agroecosistemas y sus posibles implicaciones para la conservación Trophic ecology in tadpoles of Rhinella arenarum (Anura: Bufonidae) in agroecosystems and their possible implications for conservation

El crecimiento de la agricultura produce perdida del habitat natural, con consecuencias para la biodiversidad de los anfibios. Se analizo la dieta y condición corporal de larvas de anuros de Rhinella arenarum que habitan agroecosistemas. Los muestreos fueron realizados en dos agroecosistemas y en un tercer sitio, no afectado por cultivos. Las larvas capturadas fueron anestesiadas, fijadas y preservadas en formaldehido, se realizaron medidas corporales y se analizo la dieta de las larvas. Se registro diversidad en la oferta alimenticia proporcionada por los distintos ambientes. La dieta tuvo una predominancia de algas Bacillarophyceae, seguidas por Cyanophyceae. Particularmente, los géneros Navicula, Nitzschia, Hantzschia y Gomphonema (clase Bacillarophyceae), fueron importantes en los agroecosistemas. Los géneros Osillatoria, Euglena y Strombomonas (clases Cyanophyceae y Euglenophyceae), predominaron en la dieta de las larvas de anuros en el sitio menos alterado. Las larvas de los sitios más alterados consumen menor cantidad de alimento y registran una menor condición corporal. La presencia de determinadas algas, indicarían un mayor grado de contaminación en los agroecosistemas. La eutrofización de lagunas podría alterar la disponibilidad de alimento para larvas de anuros que podría tener consecuencias poblacionales negativas. Se sugiere el análisis de dietas larvarias como un potencial bioindicador de salubridad ambiental.Trophic ecology in tadpoles of Rhinella arenarum (Anura: Bufonidae) in agroecosystems and their possible implications for conservation. The progress of the agriculture border has led an important loss of natural habitats, with significant consequences for biodiversity. In this sense, the studies in anuran amphibian tadpoles inhabiting these environments are relevant, because the larval stage is a phase of population regulation. The aim of this study was to analyze the body condition and diet in Rhinella arenarum, tadpoles, an anuran species widely distributed in South America and that inhabit agroecosystems. Three sites were sampled, two agroecosystems with different alteration degrees (C1 and C2) and an uncultured (SM) third place. The captured tadpoles were anesthetized, fixed and preserved in formaldehyde (10%). Subsequently, body measurements were made and the complete intestine was removed and analyzed for food items under a binocular microscope. The diet in R. arenarum tadpoles has a dominance of algae Bacillariophyceae, followed by Cyanophyceae. In particular, the class Bacillariophyceae, due to the presence of the genus Navicula, Nitzschia, Gomphonema and Hantzschia, was important in the diet of the anurans in those agroecosystems. Class Cyanophyceae, mainly represented by genus Oscillatoria and Euglenophyceae represented by Euglena and Strombomonas, were predominant in the diet of the anurans in SM. Some differences in the total items consumed by tadpole were observed between the studied sites. Tadpoles that inhabit the modified sites (C1 and C2) recorded a significantly smaller amount of food. Moreover, the tadpoles that inhabit these sites showed a lower body condition. The presence of certain algae associated with eutrophic environments, could indicate some pollution in agroecosystems (C1 and C2). Food resources would be lesser in places with strong agricultural activity, possibly with a greater degree of eutrophication. A smaller food amount could have consequences at population level for the short and long time terms, because of its impact on individual growth. Larval diet is suggested as a potential bioindicator of environmental health for these areas. Rev. Biol. Trop. 60 (2): 771-779. Epub 2012 June 01

Anuran larvae diet from agroecosystem’s ponds: environmental quality and implications for their populations

Agriculture is considered an important factor for the decline of amphibians recorded in the last decades. Intensive agriculture requires the application of great amounts of pesticides and fertilizers, consequently many aquatic habitats have been altered. The over-enrichment of waters with nutrients from agriculture causes growth of algae and cyanobacteria and the shift of the community composition toward the dominance of tolerant taxa. The aim of this study was to analyze the diet of tadpoles and the size of larvae and metamorphs of the native species Rhinella arenarum in agroecosystems of central Argentina. Four sampling sites with different degree of human disturbance were selected, three temporary ponds from agroecosystems (A1, A2, A3), and a pond in a semi-modified landscape, not affected by agriculture or cattle. The sites were visited once a week from October 2013 to January 2014. Tadpoles and metamorphs were captured, anesthetize and preserved. Morphometric parameters were measured on tadpoles and metamorphs and for 20 tadpoles the complete intestine was removed and their contents analyzed. Phosphate values were higher in agroecosystem ponds. Body size and mass of tadpoles and metamorphs were different between sites, being smaller in agricultural ponds. Diet analysis revealed that all larvae mainly consumed microalgae. Larval diets allowed differentiating the sites, larvae from A1 and A3 sites showed a diet with a similar composition and structure (with a predominance of Nitzschia palea), meanwhile larvae from A2 and SM showed different diets. In SM, the larvae mainly consumed Trachelomonas sp. Analysis of structural variables revealed a higher algal abundance in the diet of larvae from A3, a lower richness in SM and that there were no differences between sites in diversity and evenness of diets. Our hypothesis was support in part, given that resistant algae taxa were found in agroecosystem ponds and tadpoles and metamorphs were smaller, but larval diets showed higher abundance and richness. The analysis of the diet of aquatic stages of R. arenarum allowed us to know the trophic availability and environmental quality of temporary ponds from agroecosystems. </p

Ecología trófica en larvas de Rhinella arenarum (Anura: Bufonidae) en agroecosistemas y sus posibles implicaciones para la conservación

El crecimiento de la agricultura produce perdida del habitat natural, con consecuencias para la biodiversidad de los anfibios. Se analizo la dieta y condición corporal de larvas de anuros de Rhinella arenarum que habitan agroecosistemas. Los muestreos fueron realizados en dos agroecosistemas y en un tercer sitio, no afectado por cultivos. Las larvas capturadas fueron anestesiadas, fijadas y preservadas en formaldehido, se realizaron medidas corporales y se analizo la dieta de las larvas. Se registro diversidad en la oferta alimenticia proporcionada por los distintos ambientes. La dieta tuvo una predominancia de algas Bacillarophyceae, seguidas por Cyanophyceae. Particularmente, los géneros Navicula, Nitzschia, Hantzschia y Gomphonema (clase Bacillarophyceae), fueron importantes en los agroecosistemas. Los géneros Osillatoria, Euglena y Strombomonas (clases Cyanophyceae y Euglenophyceae), predominaron en la dieta de las larvas de anuros en el sitio menos alterado. Las larvas de los sitios más alterados consumen menor cantidad de alimento y registran una menor condición corporal. La presencia de determinadas algas, indicarían un mayor grado de contaminación en los agroecosistemas. La eutrofización de lagunas podría alterar la disponibilidad de alimento para larvas de anuros que podría tener consecuencias poblacionales negativas. Se sugiere el análisis de dietas larvarias como un potencial bioindicador de salubridad ambiental

Pine afforestation affects key primary producers in mountain grassland streams in Córdoba, 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; ArgentinaFil: 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; ArgentinaFil: 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; ArgentinaFil: 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; ArgentinaFil: 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; Argentin

Ecología trófica en larvas de Rhinella arenarum (Anura: Bufonidae) en agroecosistemas y sus posibles implicaciones para la conservación

El crecimiento de la agricultura produce pérdida del hábitat natural, con consecuencias para la biodiversidad de los anfibios. Se analizó la dieta y condición corporal de larvas de anuros de Rhinella arenarum que habitan agroecosistemas. Los muestreos fueron realizados en dos agroecosistemas y en un tercer sitio, no afectado por cultivos. Las larvas capturadas fueron anestesiadas, fijadas y preservadas en formaldehído, se realizaron medidas corporales y se analizó la dieta de las larvas. Se registró diversidad en la oferta alimenticia proporcionada por los distintos ambientes. La dieta tuvo una predominancia de algas Bacillarophyceae, seguidas por Cyanophyceae. Particularmente, los géneros Navicula, Nitzschia, Hantzschia y Gomphonema (clase Bacillarophyceae), fueron importantes en los agroecosistemas. Los géneros Osillatoria, Euglena y Strombomonas (clases Cyanophyceae y Euglenophyceae), predominaron en la dieta de las larvas de anuros en el sitio menos alterado. Las larvas de los sitios más alterados consumen menor cantidad de alimento y registran una menor condición corporal. La presencia de determinadas algas, indicarían un mayor grado de contaminación en los agroecosistemas. La eutrofización de lagunas podría alterar la disponibilidad de alimento para larvas de anuros que podría tener consecuencias poblacionales negativas. Se sugiere el análisis de dietas larvarias como un potencial bioindicador de salubridad ambiental

Anuran larvae diet from agroecosystem’s ponds: Environmental quality and implications for their populations

Agriculture is considered an important factor for the decline of amphibians recorded in the last decades. Intensive agriculture requires the application of great amounts of pesticides and fertilizers, consequently many aquatic habitats have been altered. The over-enrichment of waters with nutrients from agriculture causes growth of algae and cyanobacteria and the shift of the community composition toward the dominance of tolerant taxa. The aim of this study was use to analyze the diet of tadpoles and the size of larvae and metamorphs of the native species Rhinella arenarum in agroecosystems of central Argentina. Four sampling sites with different degree of human disturbance were selected, three temporary ponds from agroecosystems (A1, A2, A3), and a pond in a semimodified landscape, not affected by agriculture or cattle. The sites were visited once a week from October 2013 to January 2014. Tadpoles and metamorphs were captured, anesthetize and preserved. Morphometric parameters were measured on tadpoles and metamorphs and for 20 tadpoles the complete intestine was removed and their contents analyzed. Phosphate values were higher in agroecosystem ponds. Body size and mass of tadpoles and metamorphs were different between sites, being smaller in agricultural ponds. Diet analysis revealed that all larvae mainly consumed microalgae. Larval diets allowed differentiating the sites, larvae from A1 and A3 sites showed a diet with a similar composition and structure (with a predominance of Nitzschia palea), meanwhile larvae from A2 and SM showed different diets. In SM, the larvae mainly consumed Trachelomonas sp. Analysis of structural variables revealed a higher algal abundance in the diet of larvae from A3, a lower richness in SM and that there were no differences between sites in diversity and evenness of diets. Our hypothesis was support in part, given that resistant algae taxa were found in agroecosystem ponds and tadpoles and metamorphs were smaller, but larval diets showed higher abundance and richness. The analysis of the diet of aquatic stages of R. arenarum allowed us to know the trophic availability and environmental quality of temporary ponds from agroecosystems.Fil: Babini, María Selene. 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; ArgentinaFil: 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; ArgentinaFil: Luque, Elisa. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; ArgentinaFil: Gari, Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; ArgentinaFil: Salas, Nancy Edith. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; ArgentinaFil: Martino, Adolfo Ludovico. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentin