Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Communications Biology 420 [8 p.] EQUATEUR ANDES ZONE TROPICALE MONDE CAYAMBE COCA PARC NATIONAL CHALPI GRANDE BASSIN VERSANT 2022 fdi:010084756 ENG Communications Biology ISI:000791409700006 1 10.1038/s42003-022-03345-5 https://www.documentation.ird.fr/hor/fdi:010084756 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2022-06/010084756.pdf 5 Horizon (IRD) The growing threat of abrupt and irreversible changes to the functioning of freshwater ecosystems compels robust measures of tipping point thresholds. To determine benthic cyanobacteria regime shifts in a potable water supply system in the tropical Andes, we conducted a whole ecosystem-scale experiment in which we systematically diverted 20 to 90% of streamflow and measured ecological responses. Benthic cyanobacteria greatly increased with a 60% flow reduction and this tipping point was related to water temperature and nitrate concentration increases, both known to boost algal productivity. We supplemented our experiment with a regional survey collecting > 1450 flow-benthic algal measurements at streams varying in water abstraction levels. We confirmed the tipping point flow value, albeit at a slightly lower threshold (40-50%). A global literature review broadly confirmed our results with a mean tipping point at 58% of flow reduction. Our study provides robust in situ demonstrations of regime shift thresholds in running waters with potentially strong implications for environmental flows management. Experimental stream manipulation in a mountain river system in the tropical Andes initiates a regime shift of benthic cyanobacteria. This whole-ecosystem experiment in conjunction with a global synthesis reveal regime shift tipping points dependent upon freshwater streamflow. 036 ; 034 ; 021 UR251 Équateur