Nutrient enrichment effect on macroinvertebrates in a lowland stream of Argentina

Abstract

ABSTRACT. 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.KEYWORDS. Phosphorus, nitrogen, fertilization, invertebrate abundance, climate change.RESUMEN. 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 aument...

Variation in the distribution of Corbicula species (Mollusca: Bivalvia: Corbiculidae) after 25 years of its introduction in the Río de la Plata, Argentina

“…Also, it should be noted that there are environmental differences between the Río de la Plata and the tributary streams. Cortelezzi et al (2015) described the Argentinian pampean region streams as having: low slope (<1%), slow speed of flow, high turbidity, abundant organic matter, and elevated content of suspended solids. Their streambed consists of fine sediments (primarily silt and clay) and few stones or pebbles.…”

Impacto de agroquímicos en arroyos de cuencas rurales

“…Scheibler (2008) evaluó la composición faunística de la comunidad de invertebrados de zonas áridas en Mendoza según características propias del ambiente. Rodrigues Capítulo estudió las comunidades bentónicas de arroyos y ríos de distintas áreas de la región Pampeana afectados principalmente por efluentes urbanos e industriales (Rodrigues Capítulo et al 2003Capítulo et al , 2001Gómez et al 2008;Ocón et al 2004), como así también por el efecto de enriquecimiento de nutrientes (Cortelezzi et al 2015) y relacionadas con características del hábitat (Rodrigues Capítulo et al 2002).…”