Sedimentary dinoflagellate cyst records of human-induced environmental changes in Daya Bay, the northern South China Sea

Abstract

High resolution dinocyst records were established in sediment core to detect human-induced environmental changes in Daya Bay, the South China Sea. The grain was homogeneous except at depths of 17–18 cm, where the clay proportion increased dramatically from ∼40% to ∼80%. The 210Pb activity varied from 25.1 Bq kg−1 to 78.5 Bq kg−1 and showed temporary interruption at depths 17–18 cm associated with 1978, while dinocysts showed no obvious hiatus. Totally 36 cyst species were identified, with the highest species richness (20) and cyst abundance (900 cysts g−1) occurring at 7-cm depth, associating with severe blooms of Scrippsiella acuminate from 1998 to 2000 in Daya Bay. Cyst assemblages showed high similarity (>70%), especially in the interrupted and upper layers, indicating similar marine-originated for these intervals. Moreover, autotrophic and heterotrophic cysts dominated alternately before and after 1978, indicating high potential of the cysts to trace human-induced environmental changes in Daya Bay.