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AGRHYDROM. A timely look at effects of agriculture on fluvial DOM: the role of hydrology

During the last years, various projects as 1000 Intermittent Rivers Project, Dryflux, EuroRun or DOMIPEX, have demonstrated how collaborative experiments based on simple and inexpensive methodologies can successfully answer ecological questions that require a broad spatial coverage. In this context, in 2016, the Iberian Association of Limnology (AIL) launched its second call for Collaborative Projects among young researchers with the double aim of funding original research and promoting networking among the young researchers. During the Limnologia 2018 meeting in Coimbra, we will present the preliminary results of the awarded project: AGRHYDROM. A timely look at effects of agriculture on fluvial DOM: the role of hydrology.

Owing to the current scenario of global change, which predicts an increase in both flow intermittency and agricultural practices, in the AGRHYDROM project, we examined the combined effect of seasonal hydrological fluctuations and agriculture on nutrient concentration and dissolved organic matter (DOM) quantity and composition. We analysed the concentration of dissolved organic carbon (DOC) and nutrients (nitrogen and phosphorous), and the DOM composition by fluorescence and absorbance metrics, in 24 agricultural streams and 24 forested streams across the Iberian Peninsula and Europe (Spain, Portugal, Switzerland and Germany) thanks to a team of 66 researchers from more than 20 institutions. Moreover, to understand how flow variations modulated the influence of land use on nutrients and DOM properties, the selected streams were sampled in three phases of the hydrological cycle: base flow, contraction and expansion phases.

We hypothesize a strong interaction between hydrological variations and land use that will modulate the influence of agriculture on fluvial nutrients, DOC and DOM properties through two possible mechanisms: through changes in the buffering capacity of streams, or through the alteration of the connectivity between the streams and their catchments. The results of this project will significantly contribute to a better understanding of the effects of agricultural practices, especially on highly fluctuating small rivers, and will help to design more specific management strategies aimed to avoid the impact of agriculture on streams at times of high sensitivity.