Diversity of Dinoflagellate Cysts in Surface Sediments in the Yellow River Estuary and Its Adjacent Sea Area

Dinoflagellate cysts in the surface sediment were collected and analyzed at 16 stations in the Yellow River Estuary in 2022. Thirty-five dinoflagellate cyst taxa of thirteen genera and three uncertain taxa were identified from samples. The dominant taxa were Cyst A, Brigantedinium sp.1, Spiniferites spp., Brigantedinium spp., Operculodinium centrocarpum, Cyst C and Cyst B. Cyst richness index (d_Ma) ranged 3.66-5.91; species diversity index (H’) ranged 2.72-3.68; evenness index (J) ranged 0.53-0.73. The total cyst abundance ranged between 35 cysts/g and 921 cysts/g (in dry weight), and the average was 346 cysts/g (in dry weight). The results showed that the total abundance and diversity of dinoflagellate cysts displayed a gradually increase from both Yellow River Estuary and Laizhou Bay the central to the central Bohai Sea. The high ratio of heterotypic dinoflagellate cysts indicated a high degree of eutrophication in this sea area. The cysts of two toxic dinoflagellate species (Gonyaulax spinifera and Lingulodinium polyedrum), which produce Yessotoxin (YTX), and the cysts of three toxic dinoflagellate species (Alexandrium catenella, Alexandrium minutum and Gymnodinium catenatum ), which produce paralytic shellfish poisoning (PSP), were distributed widely in the Yellow River Estuary, but with relatively low abundance.