Impacts of multiple stressors on freshwater biota across spatial scales and ecosystems

Birk, Sebastian
Chapman, Daniel
Carvalho, Laurence
Spears, Bryan M.
Andersen, Hans Estrup
Argillier, Christine
Auer, Stefan
Baattrup-Pedersen, Annette
Banin, Lindsay
Beklioğlu, Meryem
Bondar-Kunze, Elisabeth
Borja, Angel
Branco, Paulo
Bucak, Tuba
Buijse, Anthonie D.
Cardoso, Ana Cristina
Couture, Raoul-Marie
Cremona, Fabien
de Zwart, Dick
Feld, Christian K.
Ferreira, M. Teresa
Feuchtmayr, Heidrun
Gessner, Mark O.
Gieswein, Alexander
Globevnik, Lidija
Graeber, Daniel
Graf, Wolfram
Gutierrez-Canovas, Cayetano
Hanganu, Jenica
Iskin, Ugur
Jarvinen, Marko
Jeppesen, Erik
Kotamaki, Niina
Kuijper, Marijn
Lemm, Jan U.
Lu, Shenglan
Solheim, Anne Lyche
Mischke, Ute
Moe, S. Jannicke
Noges, Peeter
Noges, Tiina
Ormerod, Steve J.
Panagopoulos, Yiannis
Phillips, Geoff
Posthuma, Leo
Pouso, Sarai
Prudhomme, Christel
Rankinen, Katri
Rasmussen, Jes J.
Richardson, Jessica
Sagouis, Alban
Santos, Jose Maria
Schaefer, Ralf B.
Schinegger, Rafaela
Schmutz, Stefan
Schneider, Susanne C.
Schuelting, Lisa
Segurado, Pedro
Stefanidis, Kostas
Sures, Bernd
Thackeray, Stephen J.
Turunen, Jarno
Uyarra, Maria C.
Venohr, Markus
von der Ohe, Peter Carsten
Willby, Nigel
Hering, Daniel
Climate and land-use change drive a suite of stressors that shape ecosystems and interact to yield complex ecological responses (that is, additive, antagonistic and synergistic effects). We know little about the spatial scales relevant for the outcomes of such interactions and little about effect sizes. These knowledge gaps need to be filled to underpin future land management decisions or climate mitigation interventions for protecting and restoring freshwater ecosystems. This study combines data across scales from 33 mesocosm experiments with those from 14 river basins and 22 cross-basin studies in Europe, producing 174 combinations of paired-stressor effects on a biological response variable. Generalized linear models showed that only one of the two stressors had a significant effect in 39% of the analysed cases, 28% of the paired-stressor combinations resulted in additive effects and 33% resulted in interactive (antagonistic, synergistic, opposing or reversal) effects. For lakes, the frequencies of additive and interactive effects were similar for all spatial scales addressed, while for rivers these frequencies increased with scale. Nutrient enrichment was the overriding stressor for lakes, with effects generally exceeding those of secondary stressors. For rivers, the effects of nutrient enrichment were dependent on the specific stressor combination and biological response variable. These results vindicate the traditional focus of lake restoration and management on nutrient stress, while highlighting that river management requires more bespoke management solutions.