Suchergebnisse

River regulation has fundamentally altered large sections of the world's river networks. The effects of dams on the structural properties of downstream reaches are well documented, but less is known about their effect on river ecosystem processes. We investigated the effect of dams on river nutrient cycling by comparing net uptake of total dissolved nitrogen (TDN), phosphorus (TDP) and organic carbon (DOC) in river reaches located upstream and downstream from three reservoir systems in the Ebro River basin (NE Iberian Peninsula). Increased hydromorphological stability, organic matter standing stocks and ecosystem metabolism below dams enhanced the whole-reach net uptake of TDN, but not that of TDP or DOC. Upstream from dams, river reaches tended to be at biogeochemical equilibrium (uptake. ≈. release) for all nutrients, whereas river reaches below dams acted as net sinks of TDN. Overall, our results suggest that flow regulation by dams may cause relevant N cycling discontinuities in rivers. Higher net N uptake capacity below dams could lead to reduced N export to downstream ecosystems. Incorporating these discontinuities could significantly improve predictive models of N cycling and transport in complex river networks ; This research was financially supported by the Spanish Ministry of Economy and Competitiveness and FEDER through the project SCARCE (Consolider-Ingenio CSD2009-00065), and by the European Union through the FP7 project GLOBAQUA (Grant agreement No 603629)

River regulation has fundamentally altered large sections of the world's river networks. The effects of dams on the structural properties of downstream reaches are well documented, but less is known about their effect on river ecosystem processes. We investigated the effect of dams on river nutrient cycling by comparing net uptake of total dissolved nitrogen (TDN), phosphorus (TDP) and organic carbon (DOC) in river reaches located upstream and downstream from three reservoir systems in the Ebro River basin (NE Iberian Peninsula). Increased hydromorphological stability, organic matter standing stocks and ecosystem metabolism below dams enhanced the whole-reach net uptake of TDN, but not that of TDP or DOC. Upstream from dams, river reaches tended to be at biogeochemical equilibrium (uptake. ≈. release) for all nutrients, whereas river reaches below dams acted as net sinks of TDN. Overall, our results suggest that flow regulation by dams may cause relevant N cycling discontinuities in rivers. Higher net N uptake capacity below dams could lead to reduced N export to downstream ecosystems. Incorporating these discontinuities could significantly improve predictive models of N cycling and transport in complex river networks ; This research was financially supported by the Spanish Ministry of Economy and Competitiveness and FEDER through the project SCARCE (Consolider-Ingenio CSD2009-00065), and by the European Union through the FP7 project GLOBAQUA (Grant agreement No 603629)

River regulation has fundamentally altered large sections of the world's river networks. The effects of dams on the structural properties of downstream reaches are well documented, but less is known about their effect on river ecosystem processes. We investigated the effect of dams on river nutrient cycling by comparing net uptake of total dissolved nitrogen (TDN), phosphorus (TDP) and organic carbon (DOC) in river reaches located upstream and downstream from three reservoir systems in the Ebro River basin (NE Iberian Peninsula). Increased hydromorphological stability, organic matter standing stocks and ecosystem metabolism below dams enhanced the whole-reach net uptake of TDN, but not that of TDP or DOC. Upstream from dams, river reaches tended to be at biogeochemical equilibrium (uptake. ≈. release) for all nutrients, whereas river reaches below dams acted as net sinks of TDN. Overall, our results suggest that flow regulation by dams may cause relevant N cycling discontinuities in rivers. Higher net N uptake capacity below dams could lead to reduced N export to downstream ecosystems. Incorporating these discontinuities could significantly improve predictive models of N cycling and transport in complex river networks ; This research was financially supported by the Spanish Ministry of Economy and Competitiveness and FEDER through the project SCARCE (Consolider-Ingenio CSD2009-00065), and by the European Union through the FP7 project GLOBAQUA (Grant agreement No 603629)

The effluents of wastewater treatment plants (WWTPs) include a complex mixture of nutrients and pollutants. Nutrients can subsidise autotrophic and heterotrophic organisms, while toxic pollutants can act as stressors, depending, for instance, on their concentration and interactions in the environment. Hence, it is difficult to predict the overall effect of WWTP effluents on river ecosystem functioning. We assessed the effects of WWTP effluents on river biofilms and ecosystem metabolism in one river segment upstream from a WWTP and three segments downstream from the WWTP and following a pollution gradient. The photosynthetic capacity and enzymatic activity of biofilms showed no change, with the exception of leucine aminopeptidase, which followed the pollution gradient most likely driven by changes in organic matter availability. The effluent produced mixed effects on ecosystem-scale metabolism. It promoted respiration (subsidy effect), probably as a consequence of enhanced availability of organic matter. On the other hand, and despite enhanced nutrient concentrations, photosynthesis-irradiance relationships showed that the effluent partly decoupled primary production from light availability, thus suggesting a stress effect. Overall, WWTP effluents can alter the balance between autotrophic and heterotrophic processes and produce spatial discontinuities in ecosystem functioning along rivers as a consequence of the mixed contribution of stressors and subsidisers ; This research was supported by the Spanish Ministry of Economy and Competitiveness and FEDER foundings through the SCARCE Consolider-Ingenio CSD2009-00065 and ABSTRACT CGL2012-35848 projects, and the European Communities 7th Framework Programme Funding under Grant agreement no. 603629-ENV-2013-6.2.1-Globaqua. We especially thank the people who assisted in the field and in the laboratory. A thorough review of the manuscript by Prof. Roger I. Jones and two unknown reviewers is deeply appreciated too. We also want to acknowledge financial support in terms of predoctoral grants from the University of the Basque Country (I. Aristi), the Basque Government (M. Arroita), as well as a postdoctoral grant 'Juan de la Cierva' (jci-2010-06397) (D. von Schiller) and a Marie Curie European Reintegration Grant (PERG07-GA-2010-259219) (V. Acuña). This work was partly supported by the Basque Government (Consolidated Research Group: Stream Ecology 7-CA-18/10)

The effluents of wastewater treatment plants (WWTPs) include a complex mixture of nutrients and pollutants. Nutrients can subsidise autotrophic and heterotrophic organisms, while toxic pollutants can act as stressors, depending, for instance, on their concentration and interactions in the environment. Hence, it is difficult to predict the overall effect of WWTP effluents on river ecosystem functioning. We assessed the effects of WWTP effluents on river biofilms and ecosystem metabolism in one river segment upstream from a WWTP and three segments downstream from the WWTP and following a pollution gradient. The photosynthetic capacity and enzymatic activity of biofilms showed no change, with the exception of leucine aminopeptidase, which followed the pollution gradient most likely driven by changes in organic matter availability. The effluent produced mixed effects on ecosystem-scale metabolism. It promoted respiration (subsidy effect), probably as a consequence of enhanced availability of organic matter. On the other hand, and despite enhanced nutrient concentrations, photosynthesis-irradiance relationships showed that the effluent partly decoupled primary production from light availability, thus suggesting a stress effect. Overall, WWTP effluents can alter the balance between autotrophic and heterotrophic processes and produce spatial discontinuities in ecosystem functioning along rivers as a consequence of the mixed contribution of stressors and subsidisers ; This research was supported by the Spanish Ministry of Economy and Competitiveness and FEDER foundings through the SCARCE Consolider-Ingenio CSD2009-00065 and ABSTRACT CGL2012-35848 projects, and the European Communities 7th Framework Programme Funding under Grant agreement no. 603629-ENV-2013-6.2.1-Globaqua. We especially thank the people who assisted in the field and in the laboratory. A thorough review of the manuscript by Prof. Roger I. Jones and two unknown reviewers is deeply appreciated too. We also want to acknowledge financial support in terms of predoctoral grants from the University of the Basque Country (I. Aristi), the Basque Government (M. Arroita), as well as a postdoctoral grant 'Juan de la Cierva' (jci-2010-06397) (D. von Schiller) and a Marie Curie European Reintegration Grant (PERG07-GA-2010-259219) (V. Acuña). This work was partly supported by the Basque Government (Consolidated Research Group: Stream Ecology 7-CA-18/10)