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Research article - Peer-reviewed, 2022

Current water quality guidelines across North America and Europe do not protect lakes from salinization

Hintz, William D.; Arnott, Shelley E.; Symons, Celia C.; Greco, Danielle A.; McClymont, Alexandra; Brentrup, Jennifer A.; Canedo-Arguelles, Miguel; Derry, Alison M.; Downing, Amy L.; Gray, Derek K.; Melles, Stephanie J.; Relyea, Rick A.; Rusak, James A.; Searle, Catherine L.; Astorg, Louis; Baker, Henry K.; Beisner, Beatrix E.; Cottingham, Kathryn L.; Ersoy, Zeynep; Espinosa, Carmen;
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Human-induced salinization caused by the use of road deicing salts, agricultural practices, mining operations, and climate change is a major threat to the biodiversity and functioning of freshwater ecosystems. Yet, it is unclear if freshwater ecosystems are protected from salinization by current water quality guidelines. Leveraging an experimental network of land-based and in-lake mesocosms across North America and Europe, we tested how salinization-indicated as elevated chloride (C-) concentration-will affect lake food webs and if two of the lowest Cl- thresholds found globally are sufficient to protect these food webs. Our results indicated that salinization will cause substantial zooplankton mortality at the lowest Cl- thresholds established in Canada (120 mg Cl-/L) and the United States (230 mg Cl-/L) and throughout Europe where Cl- thresholds are generally higher. For instance, at 73% of our study sites, Cl- concentrations that caused a >= 50% reduction in cladoceran abundance were at or below Cl thresholds in Canada, in the United States, and throughout Europe. Similar trends occurred for copepod and rotifer zooplankton. The loss of zooplankton triggered a cascading effect causing an increase in phytoplankton biomass at 47% of study sites. Such changes in lake food webs could alter nutrient cycling and water clarity and trigger declines in fish production. Current Cl- thresholds across North America and Europe clearly do not adequately protect lake food webs. Water quality guidelines should be developed where they do not exist, and there is an urgent need to reassess existing guidelines to protect lake ecosystems from human-induced salinization.


biodiversity; climate change; environmental policy; land use; water quality

Published in

Proceedings of the National Academy of Sciences of the United States of America
2022, volume: 119, number: 9, article number: e2115033119

Authors' information

Hintz, William D.
University of Toledo
Arnott, Shelley E.
Queens University - Canada
Symons, Celia C.
University of California Irvine
Greco, Danielle A.
Queens University - Canada
McClymont, Alexandra
Queens University - Canada
Brentrup, Jennifer A.
Dartmouth College
Canedo-Arguelles, Miguel
University of Barcelona
Derry, Alison M.
University of Quebec Montreal
Downing, Amy L.
Ohio Wesleyan University
Gray, Derek K.
Wilfrid Laurier University
Melles, Stephanie J.
Ryerson University
Relyea, Rick A.
Rensselaer Polytechnic Institute
Rusak, James A.
Queens University - Canada
Searle, Catherine L.
Purdue University West Lafayette Campus
Astorg, Louis
University of Quebec Montreal
Baker, Henry K.
University of California San Diego
Beisner, Beatrix E.
University of Quebec Montreal
Cottingham, Kathryn L.
Dartmouth College
Ersoy, Zeynep
University of Evora
Espinosa, Carmen
Universitat de Vic - Universitat Central de Catalunya (UVic-UCC)
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Sustainable Development Goals

SDG6 Clean water and sanitation
SDG15 Life on land

UKÄ Subject classification

Oceanography, Hydrology, Water Resources

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