A whole-ecosystem experiment reveals flow-induced shifts in a stream community.

Daniela Rosero-López, M Todd Walter, Alexander S Flecker, Bert De Bièvre, Rafael Osorio, Dunia González-Zeas, Sophie Cauvy-Fraunié, Olivier Dangles

Communications biology 2022 May 05

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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. © 2022. The Author(s).

Citation

Daniela Rosero-López, M Todd Walter, Alexander S Flecker, Bert De Bièvre, Rafael Osorio, Dunia González-Zeas, Sophie Cauvy-Fraunié, Olivier Dangles. A whole-ecosystem experiment reveals flow-induced shifts in a stream community. Communications biology. 2022 May 05;5(1):420