Large scale submarine groundwater discharge dominates nutrient inputs to China's coast

초록

Submarine groundwater discharge (SGD) is a nutrient source to coastal waters. However, most SGD estimates are restricted to a local scale and hardly distinguish contributions from fresh (FSGD) and recirculated (RSGD) SGD. Here, we compiled data on radium/radon of groundwater (n similar to 2000) and seawater (n similar to 10,000) samples along similar to 18,000 km of China's coastal seas to resolve large scale FSGD and RSGD and their associated nutrient loads. Nearshore-scale FSGD (similar to 3.56 x 10(8) m(3) d(-1)) was only 2% of the total SGD but comparable to RSGD in terms of nutrient loads. Despite large uncertainties quantified via Monte Carlo simulations, SGD was a dominant contributor to China's coastal nutrient budgets, with dissolved inorganic nitrogen, phosphorus and silicate fluxes of similar to 395, 2.9, and 581 Gmol a(-1), respectively. Total SGD accounted for 19-54% of nutrient inputs, exceeding inputs from atmospheric deposition and rivers. Overall, SGD helps sustaining primary production along one of the most human-impacted marginal seas on Earth.

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