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.

海底地下水排放（SGD）连接着陆地和海洋系统，但由于难以量化，因此经常在沿海养分预算中被忽略。在本综述中，我们研究了全球200多个地点的SGD营养通量，解释了它们对生物地球化学的影响，并讨论了更广泛的管理意义。在约60％的研究地点中，SGD养分通量超过了河流的输入量，其中溶解态无机氮的总SGD通量中位数为每天6.0 mmol m ^-2，溶解态无机磷的日均SGD通量为每天0.1 mmol m ^-2和6.5 mmol m ^-2。每天用于溶解的硅酸盐。SGD的氮输入（主要是铵和溶解的有机氮形式）通常可以减轻沿海水域的氮限制，因为SGD倾向于具有相对于磷高的氮浓度（76％的研究表明N：P值高于Redfield比率）。值得注意的是，尽管它们具有不同的性质，但大多数研究并未区分盐水和新鲜的SGD。盐水SGD是普遍存在的，分散的途径，向全球沿海水域释放大部分再循环的养分，而新鲜的SGD有时是新养分的局部，局部来源。在水质管理计划中必须考虑源自SGD的养分通量，因为如果管理不当，这些投入会促进富营养化。