Local and regional drivers of headwater streams metabolism: insights from the first AIL collaborative project

espanolLos ecosistemas fluviales tienen un papel relevante en los ciclos biogeoquimicos globales, ya que procesan el material de la cuenca y lo transportan rio abajo. Sin embargo, los factores que afectan al metabolismo, especialmente aquellos que actuan en una escala espacial mas amplia, todavia no se conocen completamente. Ademas, el metabolismo fluvial puede variar a causa de cambios hidrologicos relacionados con la estacionalidad; lo que tambien hace importante incluir la variabilidad temporal para entender el funcionamiento de los rios. Mediante el uso de un experimento distribuido y coordinado, estudiamos diez rios de cabecera localizados a lo largo de cinco ecoregiones europeas durante verano y otono del 2014. Se midio la magnitud y la variabilidad de la produccion primaria bruta (PPB) y la respiracion ecosistemica (RE) mediante el metodo de canal abierto. Asi mismo, se examinaron los factores climaticos, hidrologico s y fisico-quimicos que potencialmente pueden afectar las tasas metabolicas fl uviales. Las tasas diarias de metabolismo fluvial variaron considerablemente entre rios, con valores de PPB de entre 0.06 a 4.33 g O2 m–2 dia–1, y de RE de entre 0.72 a 14.20 g O2 m–2 dia–1. Todos los rios fueron altamente heterotroficos (P/R EnglishStreams play a key role in the global biogeochemical cycles, processing material from adjacent terrestrial systems and transporting it downstream. However, the drivers of stream metabolism, especially those acting at broad spatial scales, are still not well understood. Moreover, stream metabolism can be affected by hydrological changes associated with seasonality, and thus, assessing the temporality of metabolic rates is a key question to understand stream function. This study aims to analyse the geographical and temporal patterns in stream metabolism and to identify the main drivers regulating the wholeecosystem metabolic rates at local and regional scales. Using a coordinated distributed experiment, we studied ten headwaters streams located across five European ecoregions during summer and fall 2014.We characterized the magnitude and variability of gross primary production (GPP) and ecosystem respiration (ER) with the open-channel method. Moreover, we examined several climatic, geographical, hydrological, morphological, and physicochemical variables that can potentially control stream metabolic rates. Daily rates of stream metabolism varied considerately across streams, with GPP and ER ranging from 0.06 to 4.33 g O2 m–2 d–1 and from 0.72 to 14.20 g O2 m–2 d–1, respectively. All streams were highly heterotrophic (P/R