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

GUERRA LOPEZ JOSE; ANSELMO JULIETA HILDA; CLAUDIA FEIJOÓ; FALABELLA A; LAURA MESSETA; DI FRANCO LEONARDO; CECILIA HEGOBURU

Coimbra

Congreso; XIX Congreso de la Asociación Ibérica de Limnología. Coimbra, Portugal; 2018

Universidad de Coimbra

In the last two decades, the Pampean region is undergoing a processof agricultural intensification that can potentially impact stream waterquality. In this study, we compared nitrate (NO3) and soluble reactivephosphorus (SRP) concentrations in 41 streams of the Buenos Airesprovince between 2003 and 2015. In addition, we analyzed changesin land use and cover in stream basins during the same period. Thepercentage of agricultural land use in the basins increased between2003 and 2015, while the percentage of land used assigned to cattlebreeding was reduced, but these differences were not significant.SRP concentration significantly increased in the streams in 2015compared to 2003, and this increase was not associated to changesin flow or agricultural cover but to the decrease of pH and carbonateconcentrations during the same period. This suggest that adsorptionof phosphorus to mineral particles may be an important processcontrolling SRP concentration in stream water. On the contrary, NO3concentrations were not significantly different between 2003 and2015, and their variability was best explained by regional features andagricultural land use in the basins. Considering that phosphorus isthe limiting nutrient in streams of the Pampean region, it is importantto elucidate the causes of SRP increase to implement measures forlessening the risk of eutrophication in Pampean waterbodies.