Transplanting macrophytes as a rehabilitation technique for lowland streams and their influence on macroinvertebrate assemblages.

Lowland streams are usually affected by river engineering works that produce the loss of habitat heterogeneity. Our aim was to assess the transplantation of macrophytes with different complexity into a lowland stream which was dredged and widened. Stuckenia pectinata and Hydrocleys nymphoides were collected at an extraction site and installed at a transplant site. The growth and coverage of macrophytes beds were quantified. Taxonomic richness, Shannon-Wiener diversity, abundance, composition and proportion of functional feeding groups of the macroinvertebrate assemblage presented in macrophyte beds were assessed between sites and species. The growth of both macrophytes did not differ significantly between sites and the coverage of transplanted beds increased, therefore they established at the transplant site within a short period. Regarding to macroinvertebrate assemblage, only the functional feeding groups did not show differences between sites. Moreover, the proportion of predators presented differences between macrophytes at the same site, with H. nymphoides having a higher proportion. Our study showed that this technique is suitable for reintroducing these species and is applicable in rehabilitation projects that promote the restoration of habitat heterogeneity deteriorated by river engineering works. Also, we highlight the importance of incorporate macroinvertebrate functional traits to assess the ecological status after rehabilitation.

Ecology of the non-native snail Sinotaia cf quadrata (Caenogastropoda: Viviparidae). A study in a lowland stream of South America with different water qualities.

Sinotaia quadrata is a snail native from Asia recorded for the first time in South America in 2009 in central Argentina. In 2015, this species was also found in a lowland stream with different water qualities. Our aims were to contribute to the knowledge of its population ecology and to compare the individuals from the two locations anatomically. Snails were searched at 6 sites, where physicochemical and hydraulic parameters were measured. Biological samples were also taken at two sites (S3 and S4) to study the population traits of S. cf quadrata (density, size structure, fecundity and sex ratio) and to assess the water quality through macroinvertebrates' biological indices (richness, diversity and IBPamp). Physicochemical and biological parameters allowed us classifying sites as "moderately polluted" (S3) and "heavily polluted" (S4). At S4, the population showed a lower density, larger individuals, higher fecundity and a scarce representation of young snails. The differences observed in the radula and mantle border of snails from the two geographical regions might be attributed to environmental differences. We conclude that this species is tolerant to a wide range of environmental variables which, along with its high fecundity and morphological plasticity, could allow this species to colonize neighbor streams.

Ecology of the non-native snail Sinotaia cf quadrata (Caenogastropoda: Viviparidae). A study in a lowland stream of South America with different water qualities

ABSTRACT Sinotaia quadrata is a snail native from Asia recorded for the first time in South America in 2009 in central Argentina. In 2015, this species was also found in a lowland stream with different water qualities. Our aims were to contribute to the knowledge of its population ecology and to compare the individuals from the two locations anatomically. Snails were searched at 6 sites, where physicochemical and hydraulic parameters were measured. Biological samples were also taken at two sites (S3 and S4) to study the population traits of S. cf quadrata (density, size structure, fecundity and sex ratio) and to assess the water quality through macroinvertebrates' biological indices (richness, diversity and IBPamp). Physicochemical and biological parameters allowed us classifying sites as "moderately polluted" (S3) and "heavily polluted" (S4). At S4, the population showed a lower density, larger individuals, higher fecundity and a scarce representation of young snails. The differences observed in the radula and mantle border of snails from the two geographical regions might be attributed to environmental differences. We conclude that this species is tolerant to a wide range of environmental variables which, along with its high fecundity and morphological plasticity, could allow this species to colonize neighbor streams.

Nutrient enrichment effect on macroinvertebrates in a lowland stream of Argentina / Efecto del enriquecimiento de nutrientes en macroinvertebrados en un arroyo pampeano de Argentina

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.(AU)

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.(AU)

Nutrient enrichment effect on macroinvertebrates in a lowland stream of Argentina / Efecto del enriquecimiento de nutrientes en macroinvertebrados en un arroyo pampeano de Argentina

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.

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.