Ba/Ca in foraminifera shells as a proxy of submarine groundwater discharge

Abstract

Submarine groundwater discharge (SGD) can have a profound influence on marine environments and elemental biogeochemical cycles in coastal waters. We have explored the feasibility of using Ba/Ca ratios of benthic foraminiferal shells as a proxy of SGD. Dissolved barium (DBa) displayed enrichment behavior in bottom waters indicating that SGD is a major DBa source in the Changjiang (Yangtze) Estuary. Foraminifera that lived in bottom waters with elevated 222Rn activities (high SGD) showed a larger range of Ba/Ca ratios than those that lived under low bottom water 222Rn activities (low SGD). Our findings support the view that benthic foraminiferal Ba/Ca ratios could be treated as a qualitative proxy of SGD. We propose that in areas where SGD is the main source of DBa, foraminiferal Ba/Ca ratios could be applied for long-term historical SGD records.