동중국해 북부해역과 한국 남해안의 표층퇴적물에서 와편모조류 시스트 분포

Abstract

Chapter 1. Although the morphological characteristics and distribution 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 remains limited. To investigate the diversity and distribution of dinoflagellate cysts, surface sediment samples were collected at 27 stations 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 granifera and Thoracosphaera heimii. 5 potentially harmful species were widely distributed: 3 potentially toxic species (Alexandrium catenlla complex, Lingulodinium polyedra and Protoceratium reticulatum) 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. Based on the results of RDA, the northern East China Sea and Korean coastal area were classified into 2 groups, A group with high water temperature and salinity, and B group with high nutrient, low water temperature and salinity. The A group seems to be affected by Kuroshio Water characterized by high water temperature and salinity, and in this group the dominant species were T. heimii, C. levantinum and L. granifera. The B group was dominated by S. trochoidea, Ensiculifea carinata, Spiniferities spp. and Brigantedinium spp., which is likely to be affected by the Yellow Sea Cold Water characterized by low water temperature, high nutrients in winter and Changjiang Diluted Water characterized by low salinity and high nutrient in summer.

Chapter 2. Surface sediment samples were collected at 12 stations in the northern ECS and quantitatively prepared using the traditional hydrochloric and hydrofluoric acid based palynological preparation technique and non-acid procedure (sieving) to compare the effectiveness of both methods. Using technique, Only 9 organic-walled cyst taxa were identified in the acid based palynological treated samples. The cyst assemblages in the acid treated samples were dominated by Spiniferities spp. (52.9%), Brigantedinium spp. (30.1%), Tuberculodinium vancampoae (3.4%). By contrast, high cyst diversity was observed in the non-acid treated samples. Organic-walled cysts was identified in 8 genera, 11 species and calcareous-walled cysts were also found in 5 genera, 6 species. The calcareous-walled cysts (e.g. T. heimii, C. levantinum and L. granifera) were dominated in the non-acid treated samples. These results indicated that calcareous-walled cysts were deformed or lost, mainly because the heavy acid used for the preparation of samples, caused the dissolution of the outer calcareous layer of the cysts. Therefore the non-acid technique is deemed to be both safer and more effective than the acid based palynological preparation technique for study on the cyst morphotypes and their distribution in surface sediments.