SEDIMENT BIOMARKER RECORDS OF PHYTOPLANKTON PRODUCTIVITY AND COMMUNITY STRUCTURE CHANGES OF THE NORTH YELLOW SEA AND ITS IMPLICATIONS FOR CLIMATE CHANGE AND ANTHROPOGENIC ACTIVITIES OVER THE LAST 130 YEARS

Biomarkers are now widely used in reconstruction of marine phytoplankton productivity and community structure changes. However, there are few biomarker records in the North Yellow Sea (NYS) and the Bohai Sea (BS). In this study, contents and ratios of various biomarkers for a ²¹⁰Pb dated core B25 from the North Yellow Sea are applied for the reconstruction of changes in phytoplankton productivity and community structure over the last 130 years. The results indicate that phytoplankton productivity increased gradually over the last 130 years and increased rapidly after 1975. From 1965 to 1990, the relative contribution of dinoflagellates increased and the relative contribution of diatoms decreased, but the trend was opposite since 1990. It suggests that the strengthened East Asia Winter Monsoon (EAWM) and increased terrestrial inputs caused higher phytoplankton productivity. The phytoplankton community structure changes are attributed to both anthropogenic activities and climate changes.