Submarine Groundwater Discharge (SGD) is not only a potential fresh waterresource, it also represents an important pathway for matter transfer from land to coastalseas. Here we investigate the SGD at Cabbé, a location near Monaco where groundwaterfrom a karst aquifer discharges to the Mediterranean Sea. The discharge was monitoredfor 24 hours and several parameters ( 222 Rn, 223 Ra, 224 Ra, 228 Ra, 226 Ra, salinity, tidal range,nitrate) were measured. The flux of nitrate associated with the SGD to the seawateroff Cabbé amounts to ～26.4 mmol · day -1 · m -1 representing an important nitrate sourcefor the local coastal environment. In contrast to 222 Rn, radium isotope concentrationsdo not vary with the tidal range indicating that the SGD is not a source of radium atCabbé. We therefore assume that radium isotopes may not be valuable tracers for SGDin cases of focused groundwater discharge from a karst aquifer. Along two ship transectsin the Bay of Roquebrune we measured an increase of 222 Rn landwards towards Cabbéreflecting the influence of SGD on the composition of local seawater.
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