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Disentangling multiple chemical and non-chemical stressors in a lotic ecosystem using a longitudinal approach

  • 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.

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Author:Markus Weitere, Rolf Altenburger, Christine Anlanger, Martina Baborowski, Ilona Bärlund, Liza-Marie Beckers, Dietrich Borchardt, Werner Brack, Lisa Brase, Wibke Busch, Antonis Chatzinotas, Björn Deutschmann, Jens Eligehausen, Karin Frank, Daniel Graeber, Christian Griebler, Jeske Hagemann, Peter Herzsprung, Henner Hollert, Pedro A. Inostroza, Christoph G. JägerORCiD, René Kallies, Norbert Kamjunke, Bernhard Karrasch, Sigrid Kaschuba, Andrew Kaus, Bernd Klauer, Kay Knöller, Matthias Koschorreck, Martin Krauss, Julia V. Kunz, Marie J. Kurz, Matthias Liess, Margarete Mages, Christin Müller, Matthias Muschket, Andreas Musolff, Helge Norf, Florian Pöhlein, Lena Reiber, Ute Risse-Buhl, Karl-Werner Schramm, Mechthild Schmitt-Jansen, Markus Schmitz, Ulrike Strachauer, Wolf von Tümpling, Nina Weber, Romy Wild, Christine Wolf, Mario Brauns
URL:https://doi.org/10.1016/j.scitotenv.2020.144324
Parent Title (English):Science of the Total Environment
Document Type:Article (peer reviewed)
Language:English
Publication Year:2021
Tag:Ecological functions; Effect based analyses; Indicators; Multiple stress; Running waters
Volume:769
First Page:144324
Peer reviewed:Ja
faculties / departments:Zentrum für Forschung, Entwicklung und Transfer