TY - JOUR A1 - Weitere, Markus A1 - Altenburger, Rolf A1 - Anlanger, Christine A1 - Baborowski, Martina A1 - Bärlund, Ilona A1 - Beckers, Liza-Marie A1 - Borchardt, Dietrich A1 - Brack, Werner A1 - Brase, Lisa A1 - Busch, Wibke A1 - Chatzinotas, Antonis A1 - Deutschmann, Björn A1 - Eligehausen, Jens A1 - Frank, Karin A1 - Graeber, Daniel A1 - Griebler, Christian A1 - Hagemann, Jeske A1 - Herzsprung, Peter A1 - Hollert, Henner A1 - Inostroza, Pedro A. A1 - Jäger, Christoph G. A1 - Kallies, René A1 - Kamjunke, Norbert A1 - Karrasch, Bernhard A1 - Kaschuba, Sigrid A1 - Kaus, Andrew A1 - Klauer, Bernd A1 - Knöller, Kay A1 - Koschorreck, Matthias A1 - Krauss, Martin A1 - Kunz, Julia V. A1 - Kurz, Marie J. A1 - Liess, Matthias A1 - Mages, Margarete A1 - Müller, Christin A1 - Muschket, Matthias A1 - Musolff, Andreas A1 - Norf, Helge A1 - Pöhlein, Florian A1 - Reiber, Lena A1 - Risse-Buhl, Ute A1 - Schramm, Karl-Werner A1 - Schmitt-Jansen, Mechthild A1 - Schmitz, Markus A1 - Strachauer, Ulrike A1 - von Tümpling, Wolf A1 - Weber, Nina A1 - Wild, Romy A1 - Wolf, Christine A1 - Brauns, Mario T1 - Disentangling multiple chemical and non-chemical stressors in a lotic ecosystem using a longitudinal approach JF - Science of the Total Environment N2 - Meeting ecological and water quality standards in lotic ecosystems is often failed due to multiple stressors. However, disentangling stressor effects and identifying relevant stressor-effect-relationships in complex environmental settings remain major challenges. By combining state-of-the-art methods from ecotoxicology and aquatic ecosystem analysis, we aimed here to disentangle the effects of multiple chemical and non-chemical stressors along a longitudinal land use gradient in a third-order river in Germany. We distinguished and evaluated four dominant stressor categories along this gradient: (1) Hydromorphological alterations: Flow diversity and substrate diversity correlated with the EU-Water Framework Directive based indicators for the quality element macroinvertebrates, which deteriorated at the transition from near-natural reference sites to urban sites. (2) Elevated nutrient levels and eutrophication: Low to moderate nutrient concentrations together with complete canopy cover at the reference sites correlated with low densities of benthic algae (biofilms). We found no more systematic relation of algal density with nutrient concentrations at the downstream sites, suggesting that limiting concentrations are exceeded already at moderate nutrient concentrations and reduced shading by riparian vegetation. (3) Elevated organic matter levels: Wastewater treatment plants (WWTP) and stormwater drainage systems were the primary sources of bioavailable dissolved organic carbon. Consequently, planktonic bacterial production and especially extracellular enzyme activity increased downstream of those effluents showing local peaks. (4) Micropollutants and toxicity-related stress: WWTPs were the predominant source of toxic stress, resulting in a rapid increase of the toxicity for invertebrates and algae with only one order of magnitude below the acute toxic levels. This toxicity correlates negatively with the contribution of invertebrate species being sensitive towards pesticides (SPEARpesticides index), probably contributing to the loss of biodiversity recorded in response to WWTP effluents. Our longitudinal approach highlights the potential of coordinated community efforts in supplementing established monitoring methods to tackle the complex phenomenon of multiple stress. KW - Multiple stress KW - Running waters KW - Indicators KW - Ecological functions KW - Effect based analyses Y1 - 2021 UR - https://doi.org/10.1016/j.scitotenv.2020.144324 VL - 769 SP - 144324 ER - TY - JOUR A1 - Dupas, R. A1 - Musolff, A. A1 - Jawitz, J. W. A1 - Rao, P. S. C. A1 - Jäger, Christoph G. A1 - Fleckenstein, J. H. A1 - Rode, M. A1 - Borchardt, D. T1 - Carbon and nutrient export regimes from headwater catchments to downstream reaches JF - Biogeosciences N2 - Excessive amounts of nutrients and dissolved organic matter in freshwater bodies affect aquatic ecosystems. In this study, the spatial and temporal variability in nitrate (NO3−), dissolved organic carbon (DOC) and soluble reactive phosphorus (SRP) was analyzed in the Selke (Germany) river continuum from three headwaters draining 1–3 km2 catchments to two downstream reaches representing spatially integrated signals from 184–456 km2 catchments. Three headwater catchments were selected as archetypes of the main landscape units (land use  ×  lithology) present in the Selke catchment. Export regimes in headwater catchments were interpreted in terms of NO3−, DOC and SRP land-to-stream transfer processes. Headwater signals were subtracted from downstream signals, with the differences interpreted in terms of in-stream processes and contributions from point sources. The seasonal dynamics for NO3− were opposite those of DOC and SRP in all three headwater catchments, and spatial differences also showed NO3− contrasting with DOC and SRP. These dynamics were interpreted as the result of the interplay of hydrological and biogeochemical processes, for which riparian zones were hypothesized to play a determining role. In the two downstream reaches, NO3− was transported almost conservatively, whereas DOC was consumed and produced in the upper and lower river sections, respectively. The natural export regime of SRP in the three headwater catchments mimicked a point-source signal (high SRP during summer low flow), which may lead to overestimation of domestic contributions in the downstream reaches. Monitoring the river continuum from headwaters to downstream reaches proved effective to jointly investigate land-to-stream and in-stream transport, and transformation processes. KW - Running water systems Y1 - 2017 UR - https://doi.org/10.5194/bg-14-4391-2017 VL - 14 IS - 18 SP - 4391 EP - 4407 ER -