Extent, patterns, and drivers of hypoxia in the world's streams and rivers

Hypoxia in coastal waters and lakes is widely recognized as a detrimental environmental issue, yet we lack a comparable understanding of hypoxia in rivers. We investigated controls on hypoxia using 118 million paired observations of dissolved oxygen (DO) concentration and water temperature in over 125,000 locations in rivers from 93 countries. We found hypoxia (DO < 2 mg L⁻¹) in 12.6% of all river sites across 53 countries, but no consistent trend in prevalence since 1950. High-frequency data reveal a 3-h median duration of hypoxic events which are most likely to initiate at night. River attributes were better predictors of riverine hypoxia occurrence than watershed land cover, topography, and climate characteristics. Hypoxia was more likely to occur in warmer, smaller, and lower-gradient rivers, particularly those draining urban or wetland land cover. Our findings suggest that riverine hypoxia and the resulting impacts on ecosystems may be more pervasive than previously assumed.

Presentation Preference: Oral

Primary Presenter: Alice Carter, University of Montana (alice.carter@flbs.umt.edu)

Authors:

Joanna Blaszczak, University of Nevada, Reno  (jblaszczak@unr.edu)

Lauren Koenig, United States Geological Survey  (lkoenigsnyder@usgs.gov)

Francine Mejia, United States Geological Survey  (fmejia@usgs.gov)

Lluís Gómez-Gener, Universitat Autònoma de Barcelona  (l.gomez@creaf.uab.cat)

Christopher Dutton, University of Florida  (duttonc@ufl.edu)

Alice Carter, University of Montana  (alice.carter@flbs.umt.edu)

Nancy Grimm, Arizona State University  (nbgrimm@asu.edu)

Judson Harvey, United States Geological Survey  (jwharvey@usgs.gov)

Matthew Cohen, University of Florida  (mjc@ufl.edu)