Preliminary results from a palynological study of the upper 70 meters of sediments recovered at DSDP Site 380 are presented herein. This drilling site is ideally located in the southwestern region of the Black Sea (42 degrees 05.94', 29 degrees 36.82'E) in proximity to the Bosphorus Strait, the only present-day connection between the Black Sea and the Aegean Sea. Organic-walled phytoplankton (dinoflagellate cysts, acritarchs, and fresh-water algae) are investigated to better constrain glacio-eustatic sea-level changes associated with extensive Pleistocene glacial episodes that resulted in interruption of water exchange between the Black Sea and the Aegean Sea. This study specifically focuses on quantifying changes in sea-surface salinity that are resulting from the interruption of communication between the two bodies of water. To this end, a high-precision analysis of morphological changes seen in the most abundant dinoflagellate cyst species present, Spiniferites cruciformis and Pyxidinopsis psilata, is undertaken to evaluate a possible morphological response of the cysts to changes in sea-surface salinity.