A Marine Groundwater Spring in Stoupa, Greece: Shallow Water Instrumentation Comparing Radon and Ambient Sound with Discharge Rate

This work describes the combination of two autonomous in-situ systems, one using the measurements of radon progenies and the other one using underwater ambient sound, for monitoring submarine groundwater discharge (SGD). The sensors were co-located on a platform and deployed in a SGD point source at Stoupa, Messinia, Greece. Long-term monitoring of radon progenies concentration as well as acoustic measurements are presented. The radon progeny data were correlated with the flow rate during one of the deployments. The ambient sound levels apparently responded to changes in the physical structure of the spring, but not in a predictable manner. The measuring platform can be easily applied to oceanographic survey activities, such as monitoring of gases and fluxes on submarine groundwater discharges, pockmarks, volcanoes, submarine faults, as well as to the measurement of rainfall freshwater flux at the ocean surface.