Nutrient uptake in a stream affected by hydropower plants: comparison between stream channels and diversion canals

12 páginas, 3 figuras, 4 tablas.Small hydropower plants divert part of the water from wide and physically complex stream channels with active hyporheic areas to narrow and hydraulically simple concrete canals, and thus, might affect nutrient dynamics. We compared nutrient uptake in diversion canals and in stream channels in the Leitzaran Stream (Basque Country, northern Spain). We predicted that simple morphology in diversion canals will result in lower nutrient uptake in canals than in stream channels. Periphytic chlorophyll and biomass did not differ significantly between reach types. Water was significantly deeper and faster in canals than in stream channels, but the transient storage zone did not differ significantly between reach types. There were no significant differences between uptake length for neither phosphate nor ammonium between reach types. Uptake length in both stream channels and diversion canals decreased with discharge, in a pattern similar to that previously described for pristine rivers across the world. Uptake velocity and uptake rate for phosphate did not differ signifi- cantly between reach types, but in the case of ammonium both retention metrics were significantly larger in the diversion canals. Results suggest that although hydropower schemes have minor effects on nutrient retention, these depend on the proportion of flow diverted.This research has been funded by the Spanish Department of Science and Technology, the University of the Basque Country, and the European Regional Development Fund, through projects 9/UPV00118.310-14476/ 2002 and BOS2003-04466.Peer reviewe

Pilot3 D5.2 - Verification and validation report

The deliverable provides the outcomes from the verification and validation activities carried during the course of work package 5 of the Pilot3 project, and according to the verification and validation plan defined in deliverable D5.1 (Pilot3 Consortium, 2020c). Firstly, it presents the main results of the verification activities performed during the development and testing of the different software versions. Then, this deliverable reports on the results of internal and external validation activities, which aimed to demonstrate the operational benefit of the Pilot3 tool, assessing the research questions and hypothesis that were defined at the beginning of the project. The Agile principle adopted in the project accompanying with the five five-level hierarchy approach on the definition of scenarios and case studies enabled the flexibility and tractability in the selection of experiments through different versions of prototype development. As a result of this iterative development of the tool, some of the research questions initially defined have been revisited to better reflect the validation results. The deliverable also reports the feedback received from the experts during the internal and external meetings, workshops and dedicated (on-line) site visits. During the validation campaign, both subjective qualitative information and objective quantitative data were collected and analysed to assess the Pilot3 tool. The document also summarises the results of the survey that were distributed to the external experts to assess the human-machine interface (HMI) mock-up developed in the project

Trends in stream nitrogen concentrations for forested reference catchments across the USA

To examine whether stream nitrogen concentrations in forested reference catchments have changed over time and if patterns were consistent across the USA, we synthesized up to 44 yr of data collected from 22 catchments at seven USDA Forest Service Experimental Forests. Trends in stream nitrogen presented high spatial variability both among catchments at a site and among sites across the USA. We found both increasing and decreasing trends in monthly flow-weighted stream nitrate and ammonium concentrations. At a subset of the catchments, we found that the length and period of analysis influenced whether trends were positive, negative or non-significant. Trends also differed among neighboring catchments within several Experimental Forests, suggesting the importance of catchment-specific factors in determining nutrient exports. Over the longest time periods, trends were more consistent among catchments within sites, although there are fewer long-term records for analysis. These findings highlight the critical value of long-term, uninterrupted stream chemistry monitoring at a network of sites across the USA to elucidate patterns of change in nutrient concentrations at minimally disturbed forested sites

Ecosystem respiration increases with biofilm growth and bed forms: Flume measurements with resazurin

In a set of streamside mesocosms, stream ecosystem respiration (ER) increased with biofilm biomass and flow heterogeneity (turbulence) generated by impermeable bed forms, even though those bed forms had no hyporheic exchange. Two streamside flumes with gravel beds (single layer of gravel) were operated in parallel. The first flume had no bed forms, and the second flume had 10 cm high dune-shaped bed forms with a wavelength of 1.0 m. Ecosystem respiration was measured via resazurin reduction to resorufin in each flume at three different biomass stages during biofilm growth. Results support the hypothesis that ER increases with flow heterogeneity generated by bed forms across all biofilm biomass stages. For the same biofilm biomass, ER was up to 1.9 times larger for a flume with 10 cm high impermeable bed forms than for a flume without the bed forms. Further, the amount of increase in ER associated with impermeable bed forms was itself increased as biofilms grew. Regardless of bed forms, biofilms increased transient storage by a factor of approximately 4.Keywords: bed forms, respiration, transient storage, biofilm, metabolism, resazuri

Trends in stream nitrogen concentrations for forested reference catchments across the USA

To examine whether stream nitrogen concentrations in forested reference catchments have changed over time and if patterns were consistent across the USA, we synthesized up to 44 yr of data collected from 22 catchments at seven USDA Forest Service Experimental Forests. Trends in stream nitrogen presented high spatial variability both among catchments at a site and among sites across the USA. We found both increasing and decreasing trends in monthly flow-weighted stream nitrate and ammonium concentrations. At a subset of the catchments, we found that the length and period of analysis influenced whether trends were positive, negative or non-significant. Trends also differed among neighboring catchments within several Experimental Forests, suggesting the importance of catchment-specific factors in determining nutrient exports. Over the longest time periods, trends were more consistent among catchments within sites, although there are fewer long-term records for analysis. These findings highlight the critical value of long-term, uninterrupted stream chemistry monitoring at a network of sites across the USA to elucidate patterns of change in nutrient concentrations at minimally disturbed forested sites.Keywords: forested catchment, nitrate, trends, stream, reference catchments, ammoniumKeywords: forested catchment, nitrate, trends, stream, reference catchments, ammoniu

Shifting stoichiometry: Long-term trends in stream-dissolved organic matter reveal altered C:N ratios due to history of atmospheric acid deposition

Este artículo contiene 17 páginas, 6 figuras, 2 tablas.Dissolved organic carbon (DOC) and nitrogen (DON) are important energy and nutrient sources for aquatic ecosystems. In many northern temperate, freshwater systems DOC has increased in the past 50 years. Less is known about how changes in DOC may vary across latitudes, and whether changes in DON track those of DOC. Here, we present long-term DOC and DON data from 74 streams distributed across seven sites in biomes ranging from the tropics to northern boreal forests with varying histories of atmospheric acid deposition. For each stream, we examined the temporal trends of DOC and DON concentrations and DOC:DON molar ratios. While some sites displayed consistent positive or negative trends in stream DOC and DON concentrations, changes in direction or magnitude were inconsistent at regional or local scales. DON trends did not always track those of DOC, though DOC:DON ratios increased over time for ~30% of streams. Our results indicate that the dissolved organic matter (DOM) pool is experiencing fundamental changes due to the recovery from atmospheric acid deposition. Changes in DOC:DON stoichiometry point to a shifting energynutrient balance in many aquatic ecosystems. Sustained changes in the character of DOM can have major implications for stream metabolism, biogeochemical processes, food webs, and drinking water quality (including disinfection by-products). Understanding regional and global variation in DOC and DON concentrations is important for developing realistic models and watershed management protocols to effectively target mitigation efforts aimed at bringing DOM flux and nutrient enrichment under control.National Institute of Food and Agriculture, Grant/Award Number: 1016163, 1019522 and 1022291; Natural Environment Research Council, Grant/Award Number: NE/K010689/1; NSF EPSCoR, Grant/ Award Number: EPS-1929148; Division of Environmental Biology, Grant/ Award Number: 1545288 and 1556603; European Regional Development Fund, Grant/Award Number: RTI2018-094521- B-100 and RYC-2017-22643Peer reviewe

Gradients of anthropogenic nutrient enrichment alter N Composition and DOM stoichiometry in freshwater ecosystems

Plain language summary Ammonium and nitrate in freshwaters have received considerable attention due to their clear ecological and health effects. A comprehensive assessment of N in freshwaters that includes DON is lacking. Including DON in studies of surface water chemistry is important because it can cause eutrophication and certain forms can be rapidly removed by microbial communities. Here, we document how elevated levels of TDN impact the concentrations and relative proportions of all three forms of dissolved N and the stoichiometry of DOM. Our results suggest that human activities fundamentally alter the composition of the dissolved nitrogen pool and the stoichiometry of DOM. Results also highlight feedbacks between the C and N cycles in freshwater ecosystems that are poorly studied.A comprehensive cross-biome assessment of major nitrogen (N) species that includes dissolved organic N (DON) is central to understanding interactions between inorganic nutrients and organic matter in running waters. Here, we synthesize stream water N chemistry across biomes and find that the composition of the dissolved N pool shifts from highly heterogeneous to primarily comprised of inorganic N, in tandem with dissolved organic matter (DOM) becoming more N-rich, in response to nutrient enrichment from human disturbances. We identify two critical thresholds of total dissolved N (TDN) concentrations where the proportions of organic and inorganic N shift. With low TDN concentrations (0–1.3 mg/L N), the dominant form of N is highly variable, and DON ranges from 0% to 100% of TDN. At TDN concentrations above 2.8 mg/L, inorganic N dominates the N pool and DON rarely exceeds 25% of TDN. This transition to inorganic N dominance coincides with a shift in the stoichiometry of the DOM pool, where DOM becomes progressively enriched in N and DON concentrations are less tightly associated with concentrations of dissolved organic carbon (DOC). This shift in DOM stoichiometry (defined as DOC:DON ratios) suggests that fundamental changes in the biogeochemical cycles of C and N in freshwater ecosystems are occurring across the globe as human activity alters inorganic N and DOM sources and availability. Alterations to DOM stoichiometry are likely to have important implications for both the fate of DOM and its role as a source of N as it is transported downstream to the coastal ocean

Effect of different flooding intensities on the macroinvertebrate community of the River Matarranya (Ebro basin, Spain)

12 páginas, 6 figuras, 6 tablas.[EN]In October 2000, the Matarranya River suffered an extraordinary flood with a measured flow rate of approximately 450 m3/s in the town of Vall-de-roures and a return period of about 500 years, according to the Ebro Hydrographic Confederation. The objective of this study was to determine the influence of the consequent perturbation on the structure and composition of the macroinvertebrate community and its subsequent recovery. To this end, two sites in the headwaters of the river, about which information from previous studies was available, were chosen as sampling sites. The Parrissal station, 8 km from the source with a practically natural flow regime, and at Vall-de-roures, 18 km from the source and from which part of the flow has been deviated, to be returned in summer from the waters collected in the reservoir on the Pena River. Sampling was carried out one, five and fifteen months after the flood and the data was compared with that obtained before the perturbation, (December, 1998 and February, 1999). On the other hand, we analized the effects of smaller floods occurring in October 1984 (Parrissal) and June 1986 (Vall-de-roures). The results point to different patterns of recovery in the two sampling points after the 2000 flood, the community density recovering more rapidly in the site less affected by anthropic intervention (Parrissal), while the biological quality of the stretch studied in Vall-de-roures involved increased taxonomic richness and greater structuring of the community. The flood events of lesser magnitude did not seem to affect the community structure in Parrissal, while in Vall-deroures the abundance of the predominant groups varied.[ES]El río Matarranya padeció en octubre de 2000 una riada extraordinaria, que alcanzó un caudal aproximado de 450 m3/s en la población de Vall-de-roures, con un período de retorno estimado de 500 años según la Confederación Hidrográfica del Ebro. El objetivo del presente estudio es determinar la incidencia de esta perturbación sobre la estructura y la composición de la comunidad de macroinvertebrados y su posterior recuperación. Con dicho fin se han muestreado dos estaciones de la cabecera del río de las que se posee información de estudios precedentes. La estación de Parrissal a 8 km de distancia del nacimiento es una estación con un régimen de caudales prácticamente natural y la estación de Vall-de-roures a 18 km del nacimiento, esta última ha sufrido la derivación de parte de su caudal, el cual le es retornado durante el periodo estival a través de los aportes del embalse del río Pena. Los muestreos se han realizado un mes, cinco y quince meses después de la riada y se han comparado con los datos obtenidos en dos muestreos previos a dicha perturbación (diciembre de 1998 y febrero de 1999). Por otra parte se han analizado los efectos de crecidas de menor magnitud ocurridas en octubre de 1984 en Parrissal y junio de 1986 en Vall-de-roures. Los resultados nos muestran pautas de recuperación de densidades distintas para las dos estaciones después de la riada de 2000, siendo más rápidas para la estación con un régimen de caudal natural y poca presión antrópica (estación de Parrissal), mientras que los efectos de la riada de mayor magnitud en la estación de Vall-de-roures han comportado una recuperación de la calidad biológica del tramo que ha supuesto un aumento de la riqueza taxonómica y una mayor estructuración de la comunidad. Las riadas de menor magnitud en cambio, parecen no afectar la estructura de la comunidad en Parrissal mientras que en Vall-de-roures se aprecia la variación de las abundancias de los grupos dominantes.Peer reviewe

Development of a “smart” tracer for the assessment of microbiological activity and sediment-water interaction in natural waters: the resazurin-resorufin system

10 Páginas ; 6 Figuras ; 2 Tablas (1a y 1b)A ‘‘smart’’ tracer is a tracer that provides, directly or through measurement of its concentration or in combination with another compound, at least one ‘‘bit’’ more of information about the environment through which it travels than a conservative tracer. In this study we propose and present the chemical compound resazurin as a smart tracer to assess the coupling between solute transport and microbiological activity in sediment-water interfaces in freshwaters. Resazurin is a weakly fluorescent redox-sensitive dye that undergoes an irreversible reduction to strongly fluorescent resorufin under mildly reducing conditions, most commonly in the presence of living microorganisms. To investigate the suitability of resazurin as a smart tracer, we characterized the decay, sorption, reaction, and transport behavior of resazurin and resorufin in various waters and sediments using laboratory experiments. Results show that resazurin irreversibly and rapidly reacts to resorufin in colonized sediment with pseudo-first-order behavior and a rate coefficient of 1.41 h 1. This reaction is 3 orders of magnitude faster than that in stream water alone, indicating the tracer is sensitive to microbiological activity and associated sediment-water interactions. The compounds are affected by significant sorption, with an approximately linear isotherm and a Kd of 6.63 mL/g for resorufin in sediment with 2.19% organic carbon. The compounds are stable over weeks in natural water, except in the presence of strong light where significant photochemical decay may occur more rapidly.This work was supported by sabbatical funding from the Ministerio de Educacio´n y Ciencia of Spain and Oregon State University, by funding from the NICON (MEC, Spain, ref: CGL2005– 7362) and EUROLIMPACS (EC 6th Framework Program, ref: GOCE-CT-2003-505540) projects, and by materials and conference support from the National Science Foundation (EAR 04– 09534).Peer reviewe

Resazurin as a “smart” tracer for quantifying metabolically active transient storage in stream ecosystems

14 Páginas ; 7 Figuras ; 2 Tablas[1] We propose the experimental use of resazurin (Raz) and develop a metabolically active transient storage (MATS) model to include processes that may provide additional information on transient storage from a biogeochemical perspective in stream ecosystems. Raz is a phenoxazine compound that reduces irreversibly to resorufin (Rru) in the presence of aerobic bacteria. Raz was added as a stream tracer to a 128-m reach of the forested second-order Riera de Santa Fe del Montseny (Catalonia, NE Spain), along with a conservative tracer, NaCl. Raz was transformed to Rru at a rate of 0.81 h 1 in the hyporheic zone and only at a rate of 9.9 10 4 h 1 in the stream surface channel. Raz transformation and decay and Rru production and decay were both correlated with O2 consumption measured at wells. The ratio of Raz to Rru concentration at the bottom of the reach was moderately correlated with instantaneous rates of net ecosystem production (NEP) measured over the whole reach. Data for Raz, Rru, and chloride were well fitted with the MATS model. The results from this study suggest that Raz transformation to Rru can be used as a ‘‘smart’’ tracer to detect metabolic activity, specifically aerobic respiration, associated with transient storage zones in stream ecosystems. Therefore, the Raz-Rru system can provide an assessment of the amount of transient storage that is metabolically active, an assessment that complements the physical characterization of transient storage obtained from conventional hydrologic tracers. The use of both physical and metabolic parameters of transient storage obtained with these tracers may increase our understanding of the relevance of transient storage on stream biogeochemical processes at whole reach scale, as well as the contribution of the different transient storage compartments to these processes.This work was supported by sabbatical funding from the Ministerio de Educacio´n y Ciencia of Spain and Oregon State University, by funding from the NICON (MEC, Spain, ref CGL2005–7362) and EUROLIMPACS (EC 6th Framework Program, ref GOCE-CT-2003-505540) projects, by STAMMT-L 3.0 code development from Sandia National Laboratories, and by support from the National Science Foundation (EAR 04-09534 and EAR 08-38338).Peer reviewe