Submarine groundwater discharge impacts on coastal nutrient biogeochemistry

Isaac R. Santos*, Xiaogang Chen, Alanna L. Lecher, Audrey H. Sawyer, Nils Moosdorf, Valentí Rodellas, Joseph Tamborski, Hyung Mi Cho, Natasha Dimova, Ryo Sugimoto, Stefano Bonaglia, Hailong Li, Mithra Christin Hajati, Ling Li

*Corresponding author for this work

Research output: Contribution to journalReview articleResearchpeer-review

43 Citations (Scopus)


Submarine groundwater discharge (SGD) links terrestrial and marine systems, but has often been overlooked in coastal nutrient budgets because it is difficult to quantify. In this Review, we examine SGD nutrient fluxes in over 200 locations globally, explain their impact on biogeochemistry and discuss broader management implications. SGD nutrient fluxes exceed river inputs in ~60% of study sites, with median total SGD fluxes of 6.0 mmol m−2 per day for dissolved inorganic nitrogen, 0.1 mmol m−2 per day for dissolved inorganic phosphorus and 6.5 mmol m−2 per day for dissolved silicate. SGD nitrogen input (mostly in the form of ammonium and dissolved organic nitrogen) often mitigates nitrogen limitation in coastal waters, since SGD tends to have high nitrogen concentrations relative to phosphorus (76% of studies showed N:P values above the Redfield ratio). It is notable that most investigations do not distinguish saline and fresh SGD, although they have different properties. Saline SGD is a ubiquitous, diffuse pathway releasing mostly recycled nutrients to global coastal waters, whereas fresh SGD is occasionally a local, point source of new nutrients. SGD-derived nutrient fluxes must be considered in water quality management plans, as these inputs can promote eutrophication if not properly managed.

Original languageEnglish
Pages (from-to)307-323
Number of pages17
JournalNature Reviews Earth and Environment
Issue number5
Publication statusPublished - May 2021


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