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.

中文翻译：

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全球地下河口改变了地下水对海洋的营养负荷


陆地地下水在到达大海之前穿过地下河口。地下水来源的营养物质影响沿海水质、初级生产和富营养化。我们确定了溶解性无机氮 (DIN)、溶解性无机磷 (DIP) 和溶解性有机氮 (DON) 在地下河口内的转化方式，并估算了海底地下水排放 (SGD) 养分负荷，编制了来自全球 216 个地点的超过 10,000 个地下水样本。营养物质在地下河口表现出复杂的、非保守的行为。通常会产生淡水地下水 DIN 和 DIP，而 DON 在运输过程中被消耗。 DIN、DON 和 DIP 的全球总 SGD（盐水和新鲜）通量中位数分别为 5.4、2.6 和 0.18 Tmol yr−1。尽管自然变化很大，SGD 总通量可能超过全球河流养分输出量。新鲜 SGD 是新营养物质的一小部分来源，但盐水 SGD 是大部分回收营养物质的重要来源。通过地下河口通过 SGD 输出的营养物质对于沿海生物地球化学至关重要，也是海洋的重要营养来源。