Scott D. Tiegs, David M. Costello, Mark W. Isken, Guy Woodward, Peter B. McIntyre, Mark O. Gessner, Eric Chauvet, Natalie A. Griffiths, Alex S. Flecker, Vicenc Acuna, Ricardo Albarino, Daniel C. Allen, Cecilia Alonso, Patricio Andino, Clay Arango, Jukka Aroviita, Marcus V. M. Barbosa, Leon A. Barmuta, Colden V. Baxter, Thomas D. C. Bell, Brent Bellinger, Luz Boyero, Lee E. Brown, Andreas Bruder, Denise A. Bruesewitz, Francis J. Burdon, Marcos Callisto, Cristina Canhoto, Krista A. Capps, Maria M. Castillo, Joanne Clapcott, Fanny Colas, Checo Colon-Gaud, Julien Cornut, Veronica Crespo-Perez, Wyatt F. Cross, Joseph M. Culp, Michael Danger, Olivier Dangles, Elvira de Eyto, Alison M. Derry, Veronica Diaz Villanueva, Michael M. Douglas, Arturo Elosegi, Andrea C. Encalada, Sally Entrekin, Rodrigo Espinosa, Diana Ethaiya, Veronica Ferreira, Carmen Ferriol, Kyla M. Flanagan, Tadeusz Fleituch, Jennifer J. Follstad Shah, Andre Frainer, Nikolai Friberg, Paul C. Frost, Erica A. Garcia, Liliana Garcia Lago, Pavel Ernesto Garcia Soto, Sudeep Ghate, Darren P. Giling, Alan Gilmer, Jose Francisco Goncalves, Rosario Karina Gonzales, Manuel A. S. Graca, Mike Grace, Hans-Peter Grossart, Francois Guerold, Vlad Gulis, Luiz U. Hepp, Scott Higgins, Takuo Hishi, Joseph Huddart, John Hudson, Samantha Imberger, Carlos Iniguez-Armijos, Tomoya Iwata, David J. Janetski, Eleanor Jennings, Andrea E. Kirkwood, Aaron A. Koning, Sarian Kosten, Kevin A. Kuehn, Hjalmar Laudon, Peter R. Leavitt, Aurea L. Lemes da Silva, Shawn J. Leroux, Carri J. Leroy, Peter J. Lisi, Richard MacKenzie, Amy M. Marcarelli, Frank O. Masese, Brendan G. Mckie, Adriana Oliveira Medeiros, Kristian Meissner, Marko Milisa, Shailendra Mishra, Yo Miyake, Ashley Moerke, Shorok Mombrikotb, Rob Mooney, Tim Moulton, Timo Muotka, Junjiro N. Negishi, Vinicius Neres-Lima, Mika L. Nieminen, Jorge Nimptsch, Jakub Ondruch, Riku Paavola, Isabel Pardo, Christopher J. Patrick, Edwin T. H. M. Peeters, Jesus Pozo, Catherine Pringle, Aaron Prussian, Estefania Quenta, Antonio Quesada, Brian Reid, John S. Richardson, Anna Rigosi, Jose Rincon, Geta Risnoveanu, Christopher T. Robinson, Lorena Rodriguez-Gallego, Todd V. Royer, James A. Rusak, Anna C. Santamans, Geza B. Selmeczy, Gelas Simiyu, Agnija Skuja, Jerzy Smykla, Kandikere R. Sridhar, Ryan Sponseller, Aaron Stoler, Christopher M. Swan, David Szlag, Franco Teixeira-de Mello, Jonathan D. Tonkin, Sari Uusheimo, Allison M. Veach, Sirje Vilbaste, Lena B. M. Vought, Chiao-Ping Wang, Jackson R. Webster, Paul B. Wilson, Stefan Woelfl, Marguerite A. Xenopoulos, Adam G. Yates, Chihiro Yoshimura, Catherine M. Yule, Yixin X. Zhang, Jacob A. Zwart

• River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.