Paleoenvironmental analyses of surface sediments from the Bohai Sea, China, using diatoms and silicoflagellates

Three distinct biofacies representing the Laizhou Bay, Central Bohai Sea and Bohai Strait were classified after principal component analysis. The dominant species along the salinity gradient shifted from Paralia sulcata in the Bohai Strait to Cyclotella stylorum and Dictyocha messanensis in the Laizhou Bay, while a mixing zone existed in the Central Bohai Sea. The canonical correspondence analysis between major species and environmental factors indicated a relationship between P. sulcata and the Yellow Sea intrusion, with significant positive correlations being observed between salinity gradient, water depth and autumn temperature. In comparison, C. stylorum and D. messanensis were related to the discharge of the Yellow River, having significant positive correlations with the low-salinity and nutrient-rich environment.