Global subterranean estuaries modify groundwater nutrient loading to the ocean
Stephanie J. Wilson, Amy Moody, Tristan McKenzie, M. Bayani Cardenas, Elco Luijendijk, Audrey H. Sawyer, Alicia M. Wilson, Holly A. Michael, Bochao Xu, Karen L. Knee, Hyung‐Mi Cho, Yishai Weinstein, Adina Paytan, Nils Moosdorf, Chen‐Tung Aurthur Chen, Mélanie Beck, Cody V. Lopez, Dorina Murgulet, Guebuem Kim, Mathew A. Charette, Hannelore Waska, J. Severino P. Ibánhez, Gwénaëlle Chaillou, Till Oehler, Shin‐ichi Onodera, Mitsuyo Saito, Valentí Rodellas, Natasha Dimova, Daniel Montiel, Henrietta Dulai, Christina Richardson, Jinzhou Du, Eric Petermann, Xiaogang Chen, Kay L. Davis, Sébastien Lamontagne, Ryo Sugimoto, Guizhi Wang, Hailong Li, Américo Iadran Torres, Cansu Demir, Emily Bristol, Craig T. Connolly, J. W. McClelland, Brenno Januario da Silva, Douglas R. Tait, BSK Kumar, R. Viswanadham, V. V. S. S. Sarma, Emmanoel Vieira Silva-Filho, Alan M. Shiller, Alanna L Lecher, Joseph Tamborski, Henry Bokuniewicz, Carlos Rocha, Anja Reckhardt, Michael E. Böttcher, Shan Jiang, Thomas Stieglitz, Houégnon Géraud Vinel Gbewezoun, Céline Charbonnier, Pierre Anschutz, Laura Hernández‐Terrones, S. Suresh Babu, Beata Szymczycha, Mahmood Sadat‐Noori, Felipe Niencheski, K. A. Null, Craig Tobias, Bongkeun Song, Iris C. Anderson, Isaac R. Santos
Abstract
Abstract Terrestrial groundwater travels through subterranean estuaries before reaching the sea. Groundwater‐derived nutrients drive coastal water quality, primary production, and eutrophication. We determined how dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved organic nitrogen (DON) are transformed within subterranean estuaries and estimated submarine groundwater discharge (SGD) nutrient loads compiling > 10,000 groundwater samples from 216 sites worldwide. Nutrients exhibited complex, nonconservative behavior in subterranean estuaries. Fresh groundwater DIN and DIP are usually produced, and DON is consumed during transport. Median total SGD (saline and fresh) fluxes globally were 5.4, 2.6, and 0.18 Tmol yr −1 for DIN, DON, and DIP, respectively. Despite large natural variability, total SGD fluxes likely exceed global riverine nutrient export. Fresh SGD is a small source of new nutrients, but saline SGD is an important source of mostly recycled nutrients. Nutrients exported via SGD via subterranean estuaries are critical to coastal biogeochemistry and a significant nutrient source to the oceans.