Light and flow regimes regulate the metabolism of rivers

Emily S. Bernhardt, Phil Savoy, Michael J. Vlah, Alison P. Appling, Lauren E. Koenig, Robert O. Hall, Maite Arroita, Joanna R. Blaszczak, Alice M. Carter, Matt Cohen, Judson W. Harvey, James B. Heffernan, Ashley M. Helton, Jacob D. Hosen, Lily Kirk, William H. McDowell, Emily H. Stanley, Charles B. Yackulic, Nancy B. Grimm

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Mean annual temperature and mean annual precipitation drive much of the variation in productivity across Earth's terrestrial ecosystems but do not explain variation in gross primary productivity (GPP) or ecosystem respiration (ER) in flowing waters. We document substantial variation in the magnitude and seasonality of GPP and ER across 222 US rivers. In contrast to their terrestrial counterparts, most river ecosystems respire far more carbon than they fix and have less pronounced and consistent seasonality in their metabolic rates. We find that variation in annual solar energy inputs and stability of flows are the primary drivers of GPP and ER across rivers. A classification schema based on these drivers advances river science and informs management.

Original languageEnglish
Article numbere2121976119
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number8
StatePublished - Feb 22 2022


  • Flow regimes
  • Light regimes
  • Metabolism
  • River ecosystems


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