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Este trabajo tiene por objetivo analizar el ciclo del agua en una fábrica de productos lácteos de la cuenca lechera Mar y Sierras (Argentina) e identificar los puntos ambientales críticos relacionados a la generación de efluentes líquidos en ella. Para esto, se siguieron los procedimientos de la auditoría ambiental diagnóstica, a partir de la conjunción de evidencias: fuentes secundarias, observación directa del establecimiento y la actividad productiva, estimación del volumen de agua utilizada y de los efluentes líquidos generados en un día productivo típico, análisis fisicoquímico y bacteriológico del agua de consumo y de los efluentes generados; entrevistas a un informante clave. Se identificó al lavado de la mesa desueradora y los pisos como el consumo más importante de agua en la fábrica (31% del consumo de agua diario) y a la generación de suero durante el moldeo como el punto más problemático de la generación de efluentes líquidos. En un día típico de producción se utilizan 4.246 litros de agua y se generan 4.847 litros de efluentes líquidos. Se estimó que por cada litro de leche procesada se utilizan 0,9 litros de agua, lo que indica una buena eficiencia del uso del recurso en la fábrica. Se determinó que los efluentes líquidos no poseen la calidad fisicoquímica y bacteriológica requerida por la normativa provincial para su vuelco en cuerpos de agua, por lo que se reflexionó sobre posibles formas de ahorro o revalorización del agua implicada en el proceso productivo, así como sobre medidas orientadas a mejorar el efluente que se descarga en el arroyo. Finalmente, se realizan propuestas para mejorar la eficiencia del uso de agua y del manejo de efluentes líquidos en fábricas de quesos con problemas similares. Abstract The objective of this work is to analyze the water cycle in a dairy factory from Mar y Sierras dairy basin (Argentina) and to identify the critical environmental points related to the generation of liquid effluents in it. For this, we followed the procedures of the diagnostic environmental audit, based on a combination of evidence: secondary sources, direct observation of the establishment and the productive activity, estimation of the volume of water used and of the liquid effluents generated in a typical production day, physical-chemical and bacteriological analysis of drinking water and generated effluents, and interviews with a key informant to corroborate the information obtained. The washing of the draining table and the floors was identified as the most important consumption of water in the factory (31% of the daily water consumption) and the generation of whey during molding as the most problematic point of the generation of liquid effluents. In a typical day of production, 4,246 liters of water are used and 4,847 liters of liquid effluents are generated. It was estimated that for each liter of milk processed, 0.9 liters of water are used, which indicates the efficiency of the use of the resource in the factory. It was determined that the liquid effluents do not have the physicochemical or bacteriological quality required by the provincial regulations for their discharge into water bodies. Therefore, reflection was made on possible ways of saving or revaluing the water involved in the production process, as well as on measures aimed at improving the effluent that is discharged into the stream. These proposals are considered adequate to improve the efficiency of water use and liquid effluent management in other cheese factories that pose similar problems.

Mining activity generates significant changes in the ecosystems in which it takes place, affecting the atmosphere and the surrounding aquatic and terrestrial systems, causing the destruction of landscapes, the loss of vegetation, and altering native environments. As it is an impact associated with increasing urbanization and population growth, the area occupied by quarries has increased worldwide. In the province of Buenos Aires, quarries are often abandoned without any remediation, leading to further deterioration of the ecosystem. This work aims to analyze quarrying activity’s spatiotemporal effect on the Pampean grassland in the Tandilia mountains (Buenos Aires province, Argentina). Based on Landsat 5, 7, and 8 satellite imagery, from 1996 to the present, and using QGIS software, we identified the location and extension of quarries, and we analyzed their evolution through time. Quarries currently occupy an area of 6428 ha, which was originally part of the Pampean grassland. The number of open quarries increased by 129%, from 69 in 1996 to 158 in 2022, and the area used for this activity increased by 172%, with a greater expansion being detected in the last ten years. These results conclude that this extractive activity represents a major threat to the Pampean grassland with the consequent loss of biodiversity and invasion of exotic plants capable of colonizing areas altered by human activity.

Agricultural activity is an engine of the Argentine economy, and given the extensive use of pesticides in food production, it is essential to understand their handling to assess their effects on the environment and people's health. The objective was to know the main aspects of the network of actors that use and commercialize pesticides in the Tandil district (Buenos Aires) during 2019 and 2020. Qualified referents were interviewed and agricultural producers in the area were surveyed. 10 main actors were identified, grouped into 3 categories (government agencies, civil and private associations) which proved to be linked through activities such as control, training or trade flows. The key actors agreed on the scarcity of resources assigned to control, the low use of the agronomic recipe and the diverse final destination of the empty drums. Added to this, the anthropocentric look in relation to nature, the lack of professional advice in the fields, and distrust in agroecological production is evident. The need to incorporate new actors into the network, generate public policies that allow greater control, and the urgency of undergoing a change in the productive paradigm is concluded.

Two new species of small-sized terrestrial toad of the genus Melanophryniscus from the highland grasslands of the Ventania and Tandilia Mountain Systems in Buenos Aires province, Argentina, are described. We assign provisionally Melanophryniscus diabolicus sp. nov. (Ventania mountains) and Melanophryniscus nigricans sp. nov. (Tandilia mountains) as both belonging to the Melanophryniscus stelzneri group. The new species differs from other congeners by a distinctive combination of characters: dorsum dark black, tympanum concealed, venter blackish, and distribution on highland rocky grasslands in the mountains of Tandilia (M. nigricans sp. nov.), and on highland rocky grasslands in the mountains of Ventania and coastal dune grassland (M. diabolicus sp. nov.). Moreover, the advertisement call of the new species is noticeable different between species and close related species M. atroluteus and M. montevidensis. Both species have experienced local extinctions and should be categorized as threatened species.

The use of bioindicators requires environmental information and a detailed knowledge of the biota to which it is assign a sensitivity value. The objective of this work was assessing the sensitivity of chironomids to several water quality variables. We used multivariate analysis and occupancy modelling to understand the relationship between abundance and occupancy of chironomid taxa and water quality. The study was performance in 43 sites of eight Pampean streams of Argentina during the fall in 2012 and 2015. We determined the association between 21 taxa of the chironomid assemblage and five variables of water quality (i.e., conductivity, dissolved oxygen, 5-days biochemical oxygen demand, concentrations of phosphate and dissolved inorganic nitrogen). We identified taxa associated to low water quality (e.g., Chironomus calligraphus) and high-water quality (e.g., Rheotanytarsus). In some chironomid taxa their potential as bioindicator increased as the taxonomic level decreased (e.g. Chironominae). However, in other taxa this potential as bioindicator of water quality remains at subfamily level (e.g. Orthocladiinae). The occupancy of Parachironomus sp. and Chironomus calligraphus increased in the sites with the lowest concentration of dissolved oxygen, while Rheotanytarsus sp. and Onconeura analiae behaved in an inverse way. C. calligraphus and O. analiae occupied sites with high values of both, conductivity and 5-days biochemical oxygen demand. C. calligraphus was the single species showing a positive relationship between its occupancy and concentration of phosphate. The occupancy of Allocladius neobilobulatus and Cricotopus sp. were negatively related to the increase of the concentration of nutrients. The description of species sensitivity in terms of occupancy, offers a new methodology to understand how species shows a pattern along abiotic gradient. Further studies about sensitive of local chironomid species to different types of stressors will allow researchers to generate more accurate biotic indices based on these taxa. The water quality of lowland streams would be inferred from the occupancy of chironomid taxa. Fil: Cortelezzi, Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina Fil: Simoy, Maria Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina Fil: Siri, Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; Argentina Fil: Donato, Mariano Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; Argentina Fil: Cepeda, Rosana Esther. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina Fil: Marinelli, Claudia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina Fil: Berkunsky, Igor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina

In lowland streams, channelization is a severe hydromorphological modification with negative impacts on ecosystem functioning and biological communities. We assessed the functional structure and spatial patterns of macrophyte assemblages in channelized streams, and we identified the most affected traits by this practice. We studied unchannelized (UCS) and channelized sites (CS) using a null model approach and functional diversity indices. The macrophyte coverage was higher in the UCS (mean: 86 ± 15 %) than in the CS (50 ± 35 %). Unchannelized sites revealed a random pattern, with predominating submerged and free-floating species, as well as reproduction by turions and tubers. Channelized sites showed a segregation pattern (C-score obs.: 23.08; C- core exp.: 22.20; SES: 3.20) of functionally similar species indicating interspecific competition, and lower functional richness, evenness, and Rao quadratic entropy compared to the UCS. The predominant traits found for macrophyte assemblages of these sites were emergent life form, and dispersion by stolons. Our results indicate that in CS, the abiotic environment and biotic interactions act as filters and only macrophyte species with key traits can colonize these streams. In this sense, the creation of backwater areas, the reestablishment of longitudinal and lateral connections of the streams, as well as macrophyte transplants could favor the dispersal and establishment of macrophyte species. These rehabilitation measures could positively improve the functionality of these ecosystems.

Se presentan avances de estudios ambientales sobre el recurso hídrico en sectores serranos y periserranos de Tandilia. El objetivo general fue la profundización del análisis hidrológico ambiental en la región, basado en los antecedentes del grupo de investigación. Los objetivos específicos fueron: analizar la calidad, dinámica y gestión del recurso superficial; evaluar el manejo del agua subterránea en la región identificando sus principales limitaciones y potencialidades; y el análisis comparativo del sistema hídrico subterráneo en las cuencas de los arroyos Langueyú y Del Azul. Se parte de una visión integral, considerando al agua como un componente del sistema ambiental. Para cada objetivo se aplicaron metodologías específicas, que incluyeron técnicas y herramientas de las ciencias naturales y sociales. Los principales resultados mostraron las variaciones de caudal y calidad en el arroyo Langueyú desde su cabecera hacia aguas abajo, así como de la calidad del agua y del hábitat en el balneario del arroyo Chapaleofú en Rauch. Los avances en la caracterización hidrológica del embalse del Lago del Fuerte muestran la importancia del carácter efluente de sus tributarios y la afectación por vuelcos antrópicos. Tanto en la gestión del agua superficial en la cuenca del Langueyú como en el balneario de Rauch, uno de los principales problemas detectados es la escasa o nula participación de los usuarios del recurso. El análisis en sectores periurbanos y rurales identificó también esta debilidad, y coincidió en la falta de una visión integral y de una política institucional clara. Además, de la comparación de la hidrología subterránea en las cuencas del Langueyú y Del Azul se desprende que las principales diferencias se hallan en el manejo antrópico. Se concluyó que la gestión posee falencias en las diferentes escalas de trabajo analizadas, que repercuten en la calidad y dinámica de los recursos hídricos. AbstractThe work shows the progresses achieved on the environmental studies carried out on the water resource, in hills and foothills sectors of Tandilia region. The main objective was to know in depth the environmental hydrological analysis in the region, based on the research group background studies. The specific objectives were: to analyze the quality, dynamic and management of surface resources; to evaluate the groundwater management in the region, identifying its main limitations and strengths; and the comparative analysis of the groundwater system in the Langueyú and Del Azul basins. The study starts from an integral approach, considering water as a component of the environmental system. For each objective, specific methodologies were applied, including techniques and tools of natural and social sciences. The main results showed the flow and quality variations in the Langueyú stream from its headwaters to downstream, as well as the water and habitat quality at the Chapaleofú recreation area in Rauch. The advances in the Lago del Fuerte hydrological characterization showed the importance of the relation between groundwater and surface water and the affectation by effluent discharges. Regarding to the management of surface water in the Langueyú basin and the recreation zone in Rauch, one of the main problems detected is the low or null participation by the resource’s users. The peri-urban and rural sectors analysis also identified this weakness, and the lack of a systemic approach and a strong institutional policy. Moreover, the comparison of groundwater hydrology in the Langueyú and Del Azul basins shows that the main differences are found in human management. It was concluded that water management has shortcomings in the different work levels analyzed, which have an impact on water resources quality and dynamic.

La calidad ecológica de los ecosistemas está determinada por la interacción de dos ejes principales: la calidad del hábitat y la calidad del agua. Esta interacción determina la calidad biótica del sistema, reflejada en la estructura y función de las asociaciones de macroinvertebrados, según la intensidad de cada uno de los factores que intervienen. El objetivo general de este trabajo de tesis fue evaluar la importancia del hábitat físico de arroyos de llanura de la Provincia de Buenos Aires para el establecimiento y persistencia de las poblaciones de macroinvertebrados y el mantenimiento de la calidad ecológica de los sistemas lóticos. Para esta finalidad, primeramente se analizaron los cambios fisicoquímicos (nutrientes, turbidez, DBO5, DQO, OD, pH, conductividad, temperatura y metales pesados) de tres arroyos que discurren por zonas urbanas y periurbanas (A° Martín, A° Baldovinos y A° Don Carlos) y están sometidos a diferentes modificaciones como dragados, desmalezados y canalizaciones. En cada arroyo se determinaron 3 sitios de muestreo. Luego, se realizó un análisis físico del hábitat considerando una escala de tramo y los hábitats funcionales presentes en este tipo de ambientes. En cada sitio de muestreo se registró el uso del suelo en la zona a partir del empleo de imágenes satelitales y observaciones de campo, y el tipo de modificación hidráulica en cada sitio. También se realizó un relevamiento de las plantas acuáticas presentes y su cobertura, y medidas de parámetros del cauce tales como ancho mojado, profundidad, velocidad de corriente, caudal y sustrato disponible. Dentro de cada tramo del arroyo, fueron evaluados dos mesohábitats principales: las macrófitos (emergentes, flotantes arraigadas y flotantes libres) y los sedimentos del fondo del cauce (sedimento centro y ribera). El sustrato fue clasificado de acuerdo a su granulometría como grava (> 500 μm), arena (62.5 – 500 μm), limo (3.9 – 62.5 μm) y arcilla (< 3.9 μm); también se determinó el contenido de materia orgánica en cada sitio de muestreo. Además, se aplicó un índice para la valoración del hábitat a nivel de tramo siguiendo a Barbour & Stribling (1991, 1994), quienes seleccionaron parámetros para la evaluación de arroyos de alta y baja pendiente. Este índice fue modificado para sistemas lóticos de la llanura pampeana.

Resumen extendido de la tesis elaborada para acceder al grado de “Licenciado en Diagnóstico y Gestión Ambiental” de la Facultad de Ciencias Humanas de la Universidad Nacional del Centro de la Provincia de Buenos Aires (entregada en diciembre del 2016). El trabajo tuvo como objetivo realizar un diagnóstico ambiental del uso recreativo del arroyo Chapaleofú, situado en el partido de Tandil (provincia de Buenos Aires), con el propósito de contribuir a su gestión sustentable.

The aim of the present work was to study the effect of the pyrethroid cypermethrin (CYP) on the non-target freshwater snail Chilina parchappi. Initially, the sensitivity of adult snails to CYP was evaluated via the 96-h LC50 test. Then, snails were exposed to subtethal CYP concentrations (0.1 and 10 mg/l) for 1, 4 and 10 days and the digestive glands were dissected for biomarkers analyses. Enzymatic activity of catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), as well as total glutathione reduced (GSH) levels, were determined. Histological analyses of morphology, intracellular accumulation of lipofucsins and neutral lipids accumulation in the digestive gland were also evaluated. As compared to other molluscs, C. parchappi showed high resistance to CYP exposure evidenced by the 96-h LC50 value (44.59 mg/l). Snails exposed to sublethal CYP concentrations showed a statistically significant increase (p

The critical factor in restoration and conservation of urban streams and their catchments is the human population, however the most of studies of urban ecosystems do not present social descriptors as concrete variables of analysis. The objective of this study is to perform an environmental diagnosis from a social-ecological perspective by considering both ecological and urban development descriptors of an urban basin. We selected 12 sampling sites of the Langueyu upper basin where social and ecological descriptors were determined. We arranged sampling sites according to their physicochemical characteristics (pre-urban, urban and post-urban sites). An ecological index was defined from habitat and biological descriptors: vegetation cover, richness and total density of invertebrates and organic matter. The index determined that urban and post-urban sites showed similar characteristics, and pre-urban sites presented the best habitat and biological conditions. An urbanisation index was defined from urban development descriptors: distance to the stormwater drainage network, number of industries, distance to a house without sewage, impervious surface and housing density. The results showed that the pre-urban and post-urban sites share a greater similarity in relation to the urban descriptors but with different impact in ecological quality. The headwaters in the hills (pre-urban zone) still presents a very good ecological condition (although threatened by urbanisation and tourism); however, once it crosses the dense urban area, no >5 km distance, the environmental degradation is alarming. We were able to determine that the structural measures associated with greater urbanisation, added to illegally connected sewer pipes and illegally industrial connections, produce the ecological degradation of the stream. This environmental diagnosis allowed us a deep understanding of the urbanisation impact on the ecological integrity of an urban stream in a developing country which, like many others, doesn't have monitoring programs or an integrated vision of water resources.

We assessed the effects of nutrient enrichment on three stream ecosystems running through distinct biomes (Mediterranean, Pampean and Andean). We increased the concentrations of N and P in the stream water 1.6–4-fold following a before–after control–impact paired series (BACIPS) design in each stream, and evaluated changes in the biomass of bacteria, primary producers, invertebrates and fish in the enriched (E) versus control (C) reaches after nutrient addition through a predictive-BACIPS approach. The treatment produced variable biomass responses (2–77% of explained variance) among biological communities and streams. The greatest biomass response was observed for algae in the Andean stream (77% of the variance), although fish also showed important biomass responses (about 9–48%). The strongest biomass response to enrichment (77% in all biological compartments) was found in the Andean stream. The magnitude and seasonality of biomass responses to enrichment were highly site specific, often depending on the basal nutrient concentration and on windows of ecological opportunity (periods when environmental constraints other than nutrients do not limit biomass growth). The Pampean stream, with high basal nutrient concentrations, showed a weak response to enrichment (except for invertebrates), whereas the greater responses of Andean stream communities were presumably favored by wider windows of ecological opportunity in comparison to those from the Mediterranean stream. Despite variation among sites, enrichment globally stimulated the algal-based food webs (algae and invertebrate grazers) but not the detritus-based food webs (bacteria and invertebrate shredders). This study shows that nutrient enrichment tends to globally enhance the biomass of stream biological assemblages, but that its magnitude and extent within the food web are complex and are strongly determined by environmental factors and ecosystem structure

Presentamos el primer registro de Batrachochytrium dendrobatidis infectando poblaciones amenazadas del sapito de panza roja de Tandil (Melanophryniscus aff. montevidensis). Obtuvimos muestras de hisopados de piel de 32 individuos cuyos resultados indicaron una prevalencia del 35.5% y niveles de infección que variaron entre 0.34-915 equivalentes genómicos de Batrachochytrium dendrobatidis. Este hallazgo representa una nueva amenaza que, conjuntamente con la alta fragmentación del hábitat, podría estar afectando la viabilidad de las poblaciones estudiadas. We present the first record of Batrachochytrium dendrobatidis (Bd) infecting endangered populations of the Tandilean Red-belly toad (Melanophryniscus aff. montevidensis). We obtained skin swab samples of 32 individuals. The prevalence was 35.5% and the infection levels varied between 0.34 and 915 Bd-genomic equivalents. This finding represents a new threat that could be affecting, in conjunction with the high habitat fragmentation, the viability of the studied populations. Fil: Agostini, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Cortelezzi, Agustina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Berkunsky, Igor. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Soler, Gabriela. Instituto Superior de Formación Docente y Técnica Nº 10 “Dr. Osvaldo Zarini”; Argentina Fil: Burrowes, Patricia. Universidad de Puerto Rico; Puerto Rico

The objective of this work was assessing the sensitivity of leeches to several water quality attributes in lowlands streams.Weused occupancymodelling that account explicitly for detectability, to estimate the influence of four variables (dissolved oxygen, 5-days biochemicals oxygen demand, conductivity, and dissolved inorganic nitrogen) affecting nine species. We described the sensitivity as a change in the occupancy along the range of water quality attributes.We found at least one species of Helobdella in 81% of sites and Helobdella, as genus, was detected along the entire gradient of each attribute. However, differences in the sensitivitywere observed between species. For example, if we analyse the sensitivity of the genus Helobdella to dissolved oxygen, we can say that it is very tolerant. However, if we analyse the response to dissolved oxygen of each one of the species of Helobdella,wewill realize that H. michaelseni, and H. simplex showed a high occupancy at high levels of dissolved oxygen; while H. hyalina and H. triserialis lineata showed high occupancy at low levels. Describe the sensitivity of the species in terms of occupancy, offers a new methodology to understand how the species behave along a stressor gradient., Instituto de Limnología "Dr. Raúl A. Ringuelet", Facultad de Ciencias Naturales y Museo

The objective of the present article is to propose an index that allows the assessment of the fluvial habitat quality in lowland streams that run through urbanized areas, by the use of metrics related to the quality of the watercourse, the river banks, the riparian zone and the fluvial geomorphology. The metrics retained in the index (USHI, Urban Stream Habitat Index) include the cover percentage and quality of the aquatic vegetation; the main features of the river banks; the presence of exotic trees, of litter, of permanent structures (such as buildings) in the riparian zone and other major geomorphological alterations, such as dredging or channelization. The index is related to physical-chemical parameters that are linked to water quality, the imperviousness of the watershed and to other biotic descriptors, particularly the macroinvertebrate and diatom assemblages. The values of the index for the sites in the studied area revealed that 41.2% have a bad or very bad habitat quality, 27.8% a moderate habitat quality, while 31% have a good or very good habitat quality. The main issue detected in the studied sites involved the dredging or partial channelization of the reaches. Unlike other indices that evaluate the quality of the physical habitat through the use of the diatoms or macroinvertebrate communities, the USHI can be interpreted as a measure of the overall quality of the habitat, and uses indicators that do not require the identification of taxa, making it more accessible to non-specialists. Therefore it provides with a tool to evaluate the fluvial habitat quality of lowland streams that can be easily applied, particularly by professionals that take part in the management and decision making process regarding urbanized watersheds., Instituto de Limnología "Dr. Raúl A. Ringuelet"

Biotic descriptors — both taxonomic (diversity indices, species richness, and indicator species) and nontaxonomic (biomass, oxygen consumption/production, and anatomical deformities) — are useful tools for measuring a stream's ecological condition. Nontaxonomic parameters detect critical effects not reflected taxonomically. We analyzed changes in Chironomidae populations as taxonomic parameters and mentum deformities as a nontaxonomic parameter for evaluating a South-American-plains stream (Argentina). We performed samplings seasonally (March, June, September, and December; 2005) and physical and chemical measurements at three sampling sites of the stream (DC1 at river source, through DC3 downstream). The specimens collected in sediment and vegetation were analyzed to investigate mouth deformities in Chironomidae larvae. We identified a total of 9 taxa from Chironomidae and Orthocladiinae subfamilies. Shannon's diversity index for Chironomidae decreased from 1.6 bits ind − 1 (DC1) to 0.3 bits ind − 1 (DC3). The total density of the Chironomidae exhibited a great increase in abundance at site DC3, especially that of Chironomus calligraphus. Chironomidae taxonomic composition also changed among the three sites despite their spatial proximity: C. calligraphus , Goeldichironomus holoprasinus , Parachironomus longistilus , and Polypedilum were present at all three; Corynoneura and Paratanytarsu at DC1 only; Cricotopus at DC1 and DC3; Apedilum elachistus notably at DC2 and DC3; and Parametriocnemus only at DC2. C. calligraphus individuals from DC1 showed no mentum deformities; only 2 from DC2 exhibited mouth-structure alterations; while specimens from DC3 presented the most abnormalities, especially during autumn and late winter. Type-II deformities (supernumerary teeth and gaps) were the most common. Anatomical deformities are sublethal effects representing an early alert to chemically caused environmental degradation. Mentum deformities in benthic-Chironomidae larvae constitute an effective biological-surveillance tool for detecting adverse conditions in sediments and evaluating sediment-quality-criteria compliance. Taxonomic (community composition) and nontaxonomic (condition of larval mouth parts) descriptors, used together, can indicate a stream's ecological state.

The objectives of the present study were to describe the species composition, diversity and distribution of the zoobenthic assemblages, to estimate the abundance and biomass of the dominant species, and to identify the main environmental factors determining the distribution patterns of the invertebrates from a freshwater to an estuarine zone in a temperate estuary of South America. The Río de la Plata estuary is a microtidal system characterized by a high concentration of suspended solids. Fifty-three taxa of meso- and macro-invertebrates were identified in the samples collected during November and December 2001. Molluscs, annelids, crustaceans and nematodes were found at 90% of the sampling sites. Molluscs comprised up to about 90% of the total zoobenthos biomass: the remaining percentage corresponded mainly to annelids and less to nematodes and crustaceans. An ecocline along the salinity gradient could be observed for the benthic assemblages from the freshwater to the estuarine zone in Rio de la Plata. A Canonical Correspondence Analysis shows that results from sampling sites in the outer zone were strongly related to salinity, depth and pH and less to oxygen and percentage of clay. The results from stations in the inner zone, and part of the middle zone, were mainly related to the occurrence of sand and contents of NH4+–N, NO3−–N, and PO43−–P. Fil: Cortelezzi, Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología ; Argentina Fil: Rodrigues Capitulo, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología ; Argentina Fil: Boccardi, Lucía. Universidad de la República. Facultad de Ciencias; Uruguay Fil: Arocena, Rafael. Universidad de la República. Facultad de Ciencias; Uruguay

In this study, we analyse spatial patterns of macrobenthic communities of the Río de la Plata system, and assess the species turnover or beta diversity and its relationship with environmental gradients. Macrobenthic samples and physico-chemical parameters were collected from 20 sampling sites along a transect of 560 km, including the freshwater (FW), estuarine (ES) and marine (MA) sectors. Three main assemblages corresponding to the above mentioned sectors were defined with multivariate analysis (cluster, MDS). In total 134 taxa were recorded, 81 in MA, 33 in FW and 38 in ES, represented mainly by polychaete, mollusc and crustacean species. Depth, salinity and %clay showed the strongest correlation with the observed faunal patterns (ρw=0.62; BIO-ENV analysis). Beta diversity varied between dominant taxonomic groups and was positively correlated with changes in salinity. The high variability in the composition of assemblages was reflected in beta diversity, reaching its highest values at the boundaries between the defined sectors. This study suggests that beta diversity represents a useful tool to define ecological boundaries for benthic communities in the Río de la Plata.

The selection of breeding sites in response to temporary pond characteristics has been frequently documented in several anuran species. Small and shallow temporary ponds are usually preferred. The Tandilean red-belly toad, Melanophryniscus aff. montevidensis, is an endemic species that breeds in temporary ponds of remnants of highland grasslands in Tandilia mountain system, Buenos Aires Province, Argentina. The goals of this work are to characterize breeding sites of Tandilean red-belly toad, and to assess the availability of potential breeding sites at remnants of highland grasslands. Tandilean red-belly toad was observed using ponds and temporary creeks in valleys and slopes of mountains. The median of dimensions for the breeding sites was 8m length, 4m wide and 10cm depth (n = 40). The majority of the breeding sites were circular and of natural origin. The dominant breeding site substrates were mud and vegetation. We found 115 potential breeding sites in grassland remnants of surroundings of Tandil city, giving a density of 7.1 potential breeding sites/km2. The density of potential breeding sites in highland grasslands of Tandilia Mountains was similar in most surveyed remnants. Therefore, our results suggest that size of remnant is not affecting the breeding habitat availability., Facultad de Ciencias Naturales y Museo

One of the most important effects derived from the intensive land use is the increase of nutrient concentration in the aquatic systems due to superficial drainage. Besides, the increment of precipitations in South America connected to the global climate change could intensify these anthropic impacts due to the changes in the runoff pattern and a greater discharge of water in the streams and rivers. The pampean streams are singular environments with high natural nutrient concentrations which could be increased even more if the predictions of global climate change for the area are met. In this context, the effect of experimental nutrient addition on macroinvertebrates in a lowland stream is studied. Samplings were carried out from March 2007 to February 2009 in two reaches (fertilized and unfertilized), upstream and downstream from the input of nutrients. The addition of nutrients caused an increase in the phosphorus concentration in the fertilized reach which was not observed for nitrogen concentration. From all macroinvertebrates studied only two taxa had significant differences in their abundance after fertilization: Corbicula fluminea and Ostracoda. Our results reveal that the disturbance caused by the increase of nutrients on the benthic community depends on basal nutrients concentration. The weak response of macroinvertebrates to fertilization in the pampean streams could be due to their tolerance to high concentrations of nutrients in relation to their evolutionary history in streams naturally enriched with nutrients. Further research concerning the thresholds of nutrients affecting macroinvertebrates and about the adaptive advantages of taxa in naturally eutrophic environments is still needed. This information will allow for a better understanding of the processes of nutrient cycling and for the construction of restoration measures in natural eutrophic ecosystems., Uno de los efectos más importantes derivados del uso intensivo de la tierra es el aumento de la concentración de nutrientes en los sistemas acuáticos debido al escurrimiento superficial. Además, el incremento de las precipitaciones en América del Sur vinculado al cambio climático global podría intensificar estos impactos antrópicos debido a los cambios en los patrones de escurrimiento y una mayor descarga de agua en los arroyos y ríos. Los arroyos pampeanos son ambientes particulares, con altas concentraciones basales de nutrientes, que podrían incrementarse aún más si las predicciones del cambio climático global se cumplen. En este contexto, se estudió el efecto de la adición experimental de nutrientes en un arroyo pampeano sobre los macroinvertebrados. Los muestreos se llevaron a cabo entre marzo de 2007 y febrero de 2009 en dos tramos seleccionados, aguas arriba y aguas abajo de la entrada de nutrientes. La adición de nutrientes causó un aumento en la concentración de fósforo en el tramo fertilizado, lo que no se observó para la concentración de nitrógeno. De todos los macroinvertebrados estudiados sólo dos taxa tuvieron diferencias significativas en su abundancia después de la fertilización: Corbicula fluminea y ostrácodos. Nuestros resultados revelaron que la perturbación causada por el aumento de nutrientes en una comunidad bentónica depende de la concentración basal de nutrientes. La respuesta débil de macroinvertebrados a la fertilización en las corrientes pampeanas podría ser debido a su tolerancia a altas concentraciones de nutrientes de acuerdo a su historia evolutiva en arroyos enriquecidos naturalmente con nutrientes. Se necesitan nuevas investigaciones sobre los umbrales a partir de los cuales los macroinvertebrados podrían verse afectados y sobre las ventajas adaptativas de los taxones en ambientes eutróficos naturales. Esta información nos permitirá comprender mejor los procesos de reciclaje de nutrientes y así poder pensar medidas de restauración de ecosistemas eutróficos naturales., Facultad de Ciencias Naturales y Museo, Instituto de Limnología "Dr. Raul A. Ringuelet"

We assessed the effects of nutrient enrichment on three stream ecosystems running through distinct biomes (Mediterranean, Pampean and Andean). We increased the concentrations of N and P in the stream water 1.6–4-fold following a before–after control–impact paired series (BACIPS) design in each stream, and evaluated changes in the biomass of bacteria, primary producers, invertebrates and fish in the enriched (E) versus control (C) reaches after nutrient addition through a predictive-BACIPS approach. The treatment produced variable biomass responses (2–77% of explained variance) among biological communities and streams. The greatest biomass response was observed for algae in the Andean stream (77% of the variance), although fish also showed important biomass responses (about 9–48%). The strongest biomass response to enrichment (77% in all biological compartments) was found in the Andean stream. The magnitude and seasonality of biomass responses to enrichment were highly site specific, often depending on the basal nutrient concentration and on windows of ecological opportunity (periods when environmental constraints other than nutrients do not limit biomass growth). The Pampean stream, with high basal nutrient concentrations, showed a weak response to enrichment (except for invertebrates), whereas the greater responses of Andean stream communities were presumably favored by wider windows of ecological opportunity in comparison to those from the Mediterranean stream. Despite variation among sites, enrichment globally stimulated the algal-based food webs (algae and invertebrate grazers) but not the detritus-based food webs (bacteria and invertebrate shredders). This study shows that nutrient enrichment tends to globally enhance the biomass of stream biological assemblages, but that its magnitude and extent within the food web are complex and are strongly determined by environmental factors and ecosystem structure., Instituto de Limnología "Dr. Raúl A. Ringuelet"

Our objective was to assess the effect of the physical habitat degradation in three lowland streams of Argentina that are subject to different land uses. To address this matter, we looked into some physical habitat alterations, mainly the water quality and channel changes, the impact on macrophytes’ community, and the structural and functional descriptors of the epipelic biofilm and invertebrate assemblages. As a consequence of physical and chemical perturbations, we differentiated sampling sites with different degradation levels. The low degraded sites were affected mainly for the suburban land use, the moderately degraded sites for the rural land use, and the highly degraded sites for the urban land use. The data shows that the biotic descriptors that best reflected the environmental degradation were vegetation cover and macrophytes richness, the dominance of tolerant species (epipelic biofilm and invertebrates), algal biomass, O₂ consumption by the epipelic biofilm, and invertebrates’ richness and diversity. Furthermore, the results obtained highlight the importance of the macrophytes in the lowland streams, where there is a poor diversification of abiotic substrates and where the macrophytes not only provide shelter but also a food source for invertebrates and other trophic levels such as fish. We also noted that both in benthic communities, invertebrates and epipelic biofilm supplied different information: the habitat’s physical structure provided by the macrophytes influenced mainly the invertebrate descriptors; meanwhile, the water quality mainly influenced most of the epipelic biofilm descriptors., Facultad de Ciencias Naturales y Museo, Instituto de Limnología "Dr. Raúl A. Ringuelet"

Aim: This study evaluated the use of oligochaetes at different levels of taxonomic resolution as environmental indicators in Argentine lowland streams affected by different land uses. Methods: Sampling sites were grouped based on the physicochemical and habitat characteristics (low-, moderate-, and high-impact disturbance). Collection of the oligochaetes samples was carried out seasonally in sediment and vegetation habitats. Results: The increases in nutrients and organic matter produced elevated densities of the Oligochaeta, but when the disturbance also involved changes in the physical habitat or enhancements in toxic substances, the abundance decreased significantly to values even lower than those of non-impacted environments. The responses of Naidinae and Tubificinae were similar. The density of the Pristininae decreased with increasing impact, but those of the Enchytraeidae and Rhyacodrilinae increased at the most highly impacted sites. The Opistocystidae were not recorded in high-impact sites. Species richness and diversity (H’) were lower in high-impact sites and even lower in sediments. Some species presented no restrictions in the habitat type or with the contamination level: Limnodrilus hoffmeisteri, Dero furcatus, D. digitata, D. pectinata, Pristina longiseta, and P. aequiseta. Moreover, Trieminentia corderoi, Slavina appendiculata, and Aulodrilus pigueti exhibited the highest abundances at low-impact sites and were not registered in high‑impact sites. Conclusions: The Oligochaeta show a relatively wide ecological valence through their extensive number of species. Although lower taxonomic levels can give information about environmental status, test-species’ sensitivities to different types and degrees of contamination will be of utmost relevance to the evaluation of ecological quality., Objetivo: Este estudo analisou as uso de oligoquetos em diferentes níveis de resolução taxonômica como indicadores ambientais em rios de planície Argentina afetadas por diferentes usos da terra. Métodos: Os sítios de amostragem foram agrupados com base nas características físico-químicas e habitat (perturbação baixa, moderada ou alta). Amostras de oligoquetos foram coletadas sazonalmente em habitats de sedimentos e vegetação. Resultados: Os aumentos de nutrientes e matéria orgânica resultaram em densidades elevadas de Oligochaeta, mas quando a perturbação também envolveu mudanças no habitat físico ou incrementos em substâncias tóxicas, a abundância diminuiu de forma significativa para valores ainda mais baixos que os de ambientes naõ perturbados. As respostas dos Naidinae e Tubificinae foram semelhantes. A densidade de Pristininae diminuiu com o aumento da perturbação, mas as densidades de Enchytraeidae e Rhyacodrilinae aumentaram nos locais mais altamente perturbados. Os Opistocystidae não ocorreram em locais de alta perturbação. A riqueza de espécies e a diversidade (H’) foram menores em locais de perturbação elevada e ainda mais baixos nos sedimentos. Algumas espécies não apresentaram restrições no tipo de habitat ou com o nível de contaminação: Limnodrilus hoffmeisteri, Dero furcatus, D. digitata, D. pectinata, Pristina longiseta e P. aequiseta. Além disso, Trieminentia corderoi, Slavina appendiculata e Aulodrilus pigueti exibiram uma maior abundância em locais de baixa perturbação e não foram registrados em locais com elevadas perturbações. Conclusões: Os Oligochaeta apresentaram uma valência ecológica relativamente ampla, através de seu extensivo número de espécies. Embora os níveis taxonômicos mais baixos podem dar informações sobre o status ambiental, testes com espécies com diferentes sesibilidades para diferentes tipos e graus de contaminação serão da maior relevância para a avaliação da qualidade ecológica., Instituto de Limnología "Dr. Raúl A. Ringuelet"

We explored the effects of a textile industry effluent on water quality, habitat quality and structural and functional responses of benthic communities in a lowland stream. Two sampling sites were selected: site 1 was located 300 m upstream of the outflow from the textile factory and site 2 was 500 m downstream from the discharge point. Samples of water, microbenthos, invertebrates and aquatic plants were taken seasonally. The effluent from the textile industry modified the structure of the microbenthic assemblages downstream, increased the density of organisms and the biomass of primary producers, but diminished the species richness. The oxygen consumption of the microbenthic community was 3 x higher downstream of the effluent and abnormal frustules of diatoms were noticed. The richness and abundance of invertebrate taxa were lower at the impacted site. The invertebrate modes of existence and the functional feeding groups were also significantly affected. This study is an important baseline for assessment of lowland streams with high water residence time and a notable development of hydrophytes. It will also provide a baseline for the monitoring and restoration, or remediation, programs using the metrics of biotic integrity, particularly in South American countries where such metrics are rarely employed.