Physiological reactions in plants visualized by ¹⁴C: The impact of sea spray on radiocarbon analyses of terrestrial plants in coastal regions quantified by a greenhouse study

Abstract Marine aerosols can enter the terrestrial environment via sea spray which is known to affect the stable isotope fingerprint of coastal samples (plants, animals/humans), including δ 13 C. However, the impact of sea spray on 14 C dating of terrestrial organisms at coastal sites has not been investigated so far. Besides a direct effect, sea spray is accompanied by physiological effects, e.g., due to salinity. In an artificial sea spray experiment in the greenhouse, the effect of sea spray on 14 C in plant tissue was investigated. Beach grass was sprayed with mineral salt solutions containing only traces of NaCl or with brackish water from the Schlei inlet or the Baltic Sea. These plants should give a 14 C signal close to the modern atmospheric 14 CO 2 composition. However, three treatment groups showed variable radiocarbon concentrations. Plants sprayed with water from the Schlei inlet, Baltic Sea water, or with a mineral salt solution with very high HCO 3 – concentration are depleted in 14 C content relative to contemporary atmospheric composition. While δ 13 C reflects physiological effects in the plants, caused either by salinity (NaCl) or HCO 3 – stress, resulting in decreased discrimination against 13 C, the uptake of high amounts of 14 C (ca. 53–67%) from DIC (dissolved inorganic carbon) partly masks the underlying physiological reactions, as is visible in the radiocarbon signature of the plant tissues. This preliminary study indicates that sea spray effects on plant tissue could potentially influence faunal tissue 14 C composition at coastal sites. Further research is required to better understand the observed reservoir effect.