Department of Geography and Environment, Bar-Ilan University, Ramat-Gan, 52900 Israel.
Environ Sci Technol. 2011 Jun 15;45(12):5195-200. doi: 10.1021/es104394r. Epub 2011 May 25.
Submarine groundwater discharge (SGD) is a major process operating at the land-sea interface. Quantifying the SGD nutrient loads and the marine/terrestrial controls of this transport is of high importance, especially in oligotrophic seas such as the eastern Mediterranean. The fluxes of nutrients in groundwater discharging from the seafloor at Dor Bay (southeastern Mediterranean) were studied in detail using seepage meters. Our main finding is that the terrestrial, fresh groundwater is the main conveyor of DIN and silica to the coastal water, with loads of 500 and 560 mol/yr, respectively, per 1 m shoreline. Conversely, recirculated seawater is nutrient-poor, and its role is mainly as a dilution agent. The nutrient loads regenerated in the subterranean estuary (sub-bay sediment) are relatively small, consisting mostly of ammonium (24 mol/yr). On the other hand, the subterranean estuary at Dor Bay sequesters as much as 100 mol N/yr per 1 m shoreline, mainly via denitrification processes. These, and observations from other SGD sites, imply that the subterranean estuary at some coastal systems may function more as a sink for nitrogen than a source. This further questions the extent of nutrient contributions to the coastal water by some subterranean estuaries and warrants systematic evaluation of this process in various hydrological and marine trophic conditions.
海底地下水排泄 (SGD) 是陆海界面的主要作用过程。量化 SGD 的营养负荷以及这种输送的海洋/陆地控制因素非常重要，特别是在像地中海东部这样的贫营养海域。本研究使用渗流计详细研究了多里湾（地中海东南部）海底地下水排泄的营养物通量。我们的主要发现是，陆地淡地下水是 DIN 和硅向近岸水输送的主要载体，每 1 米海岸线的负荷分别为 500 和 560 摩尔/年。相反，再循环海水贫营养，主要起稀释剂的作用。地下河口（次海湾沉积物）中再生的营养负荷相对较小，主要由铵组成（24 摩尔/年）。另一方面，多里湾的地下河口每年每 1 米海岸线固定的氮多达 100 摩尔，主要通过反硝化过程。这些以及来自其他 SGD 地点的观测结果表明，在一些沿海系统中，地下河口的功能可能更多是作为氮的汇而不是源。这进一步质疑了一些地下河口对近岸水的营养物质贡献的程度，并需要在各种水文和海洋营养条件下对这一过程进行系统评估。
