Quantitative estimation of Holocene surface salinity variation in the Black Sea using dinoflagellate cyst process length

Reconstruction of salinity in the Holocene Black Sea has been an ongoing debate over the past four decades. Here we calibrate summer surface water salinity in the Black Sea, Sea of Azov and Caspian Sea with the process length of the dinoflagellate cyst Lingulodinium machaerophorum. We then apply this calibration to make a regional reconstruction of paleosalinity in the Black Sea, calculated by averaging out process length variation observed at four core sites from the Black Sea with high sedimentation rates and dated by multiple mollusk shell ages. Results show a very gradual change of salinity from ∼14 ± 0.91 psu around 9.9 cal ka BP to a minimum ∼12.3 ± 0.91 psu around 8.5 cal ka BP, reaching current salinities of ∼17.1 ± 0.91 psu around 4.1 cal ka BP. The resolution of our sampling is about 250 years, and it fails to reveal a catastrophic salinization event at ∼9.14 cal ka BP advocated by other researchers. The dinoflagellate cyst salinity-proxy does not record large Holocene salinity fluctuations, and after early Holocene freshening, it shows correspondence to the regional sea-level curve of Brückner et al. (2010) derived from Balabanov (2007).

► A new salinity proxy is calibrated to summer salinity in the Caspian – Black Sea.
► This proxy uses process length of the dinocyst Lingulodinium machaerophorum.
► Molecular data of this species from Caspian, Black Sea and California is identical.
► Quantitative salinity is reconstructed for the Holocene Black Sea in 6 cores.
► The summer surface salinity increase was gradual: 12.3–17.1 psu (∼4.8 ± 0.91 psu).