Atmospheric lightning has been the focus of many studies in atmospheric physics and chemistry. In previous studies we have shown that the intensity of electrical sparks discharged into natural and artificial saline solutions are strongly influenced by their salinity and pH. In this study we tested the effect of changes in the total alkalinity (TA) of Mediterranean seawater on its lightning flash intensity (LFI) by addition of concentrated HCl and NaOH. These experiments showed that the LFI was positively correlated with TA and varied by 40% between the lower and upper limit of our experimental range. These results imply that TA together with salinity and pH of natural waters, may also be a significant predictor of LFI, especially in oceanic regions where TA diverges positively from its conservation with salinity because of external inputs such as rivers and groundwater or upwelling of TA and CO2 enriched (low pH) deep waters.