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The intergovernmental Panel on Climate Change (IPCC, 2012) predicts increases in the frequency of heavy precipitation in the 21st century over many areas of the globe. Thus, climate change will increase flood and drought frequencies, alter stream geomorphology and habitat availability, as well as increase water temperature, sediments, and nutrient concentration (Sabater & Tockner, 2010). Current models of climate changes from Latin America anticipate that changes could significantly affect the hydrological cycle, altering the intensity and temporal and spatial distribution of precipitation, surface runoff and groundwater recharge, with various impacts on different natural ecosystems and human activities (IPCC, 1997). Rainfall changes in the Pampas are consistent with patterns observed elsewhere in South America (Haylock et al. 2006). The rainfall increase has partly contributed to major changes in land use patterns resulting in a significant expansion of the area dedicated to agriculture (Paruelo et al. 2005). The greater discharge of water combined with changes in the land use (intensive and exclusive culture of soybeans) will lead to a greater input of nutrients and contaminants into streams and rivers (Rodrigues Capítulo et al. 2010). Especially P and N concentrations are routinely affected by human activities and are expected to increase in the future in the fluvial ecosystems (Ferreiro et al. 2011).This situation will increase markedly in recent years mainly in areas with agricultural potential where the land use is disproportionately near waterways and the humans modify riparian zones extensively (Sala et al. 2000). As part of the GlobRio project: Global changes in river systems: effects on biodiversity, food web and system functioning, we explore the effect of increase the concentration of nutrient on structure of benthic assemblages in a global climate change scenario. The objective was to analyze the effect of an experimental simulation of the increase in nutrients in a pampean stream on macroinvertebrates assemblages.
