Distribution of dinoflagellate cysts in surface sediments from the northern East China Sea and Korean coastal area

Abstract

Although the morphological characteristics and distribut ion of dinoflagellate cysts have been widely investigated in many coastal areas of the world, the knowledge-base in the northern East China Sea (ECS) and Korean coastal areas remainslimited. To investigate the diversity and distribution of dinoflagellate cysts, surface sediment samples were collected at 27 station s from the northern ECS and Korean coastal area in June 2015 and May 2017. Cyst morphology was examined with light microscopy and scanning electron microscopy . A total of 30 species belonging to 16 genera dinoflagellate cyst taxa were identified. 3 unrecorded speices were observed: Calciodinellum levantinum, Leonella gramfera and Thoracosphaera heimii. 5 potentially harmful species were widely distributed: 3 potentially toxic species (Alexandrium catenlla complex, Lingulodinium polyedra and Protoceratium reaticulatum) and 2 potentially bloom-forming species (Scrippsiella trochoidea complex and Gonyaulax spinifera complex). Cyst abundance ranged from 438 to 43,167 cysts g-1 dry weight, and was higher in the northern ECS than in the Korean coastal area. The cyst assemblages were dominated by T. heimii. Redundancy analysis was used to investigate the relatio nships between cyst abundance and envirorunental factors . The first axis significantly correlated with water temperature. The best positive fit for the first axis was the relative abundance of