Changes in land use and nutrient level in streams from a region subjected to agricultural intensification (Argentine Pampas) between 2003 y 2015

GOMEZ, ALICIA; MESSETTA, M. LAURA; GUERRA-LOPEZ, JOSÉ; DI FRANCO, LEONARDO; HEGOBURU, CECILIA; FALLABELA, A; ANSELMO, JULIETA; FEIJOO, CLAUDIA

Coimbra

Congreso; XIX Congreso de la Asociación Ibérica de Limnología; 2018

Universidad de Coimbra

In the last two decades, the Pampean region is undergoing a process of agricultural intensification that can potentially impact stream water quality. In this study, we compared nitrate (NO3) and soluble reactive phosphorus (SRP) concentrations in 41 streams of the Buenos Aires province between 2003 and 2015. In addition, we analyzed changes in land use and cover in stream basins during the same period. The percentage of agricultural land use in the basins increased between 2003 and 2015, while the percentage of land used assigned to cattle breeding was reduced, but these differences were not significant. SRP concentration significantly increased in the streams in 2015 compared to 2003, and this increase was not associated to changes in flow or agricultural cover but to the decrease of pH and carbonate concentrations during the same period. This suggest that adsorption of phosphorus to mineral particles may be an important process controlling SRP concentration in stream water. On the contrary, NO3 concentrations were not significantly different between 2003 and 2015, and their variability was best explained by regional features and agricultural land use in the basins. Considering that phosphorus is the limiting nutrient in streams of the Pampean region, it is important to elucidate the causes of SRP increase to implement measures for lessening the risk of eutrophication in Pampean waterbodies.