Inverse relationship between salinity and n-alkane δD values in the mangrove Avicennia marina

► We measured D/H fractionation in mangrove leaf wax n-alkanes along an estuary. ► D/H fractionation in leaf waxes increases by ∼1.5‰ per salinity unit. ► This relationship is the opposite of that observed in phytoplankton. ► Complicates paleoclimate interpretation of leaf wax δD in regions with mangroves. ► Suggests that δD of a mangrove specific biomarker could be a paleosalinity proxy.