Distribution of dinoflagellate cysts in surface sediments of Tongyeong, South Korea: Application of a next generation sequencing method

Abstract

To characterise the distribution of dinoflagellate cysts, we used next generation sequencing (NGS) after sampling surface sediments of the Tongyeong coastal lines of South Korea. Sampling was divided into two seasons: a no red tide winter (52 sites, in December 2013) and a red tide summer (44 sites, in September 2014). The surface sediment samples were stored at 4 °C in a dark refrigerator for at least 6 months to allow decomposition of organic matter (such as living phytoplankton). The NGS analysis revealed 5,270&#8211 13,979 read counts and 175&#8211 273 operational taxonomic units (OTUs) with 97% sequence similarity obtained after quality filtering that included the selection of >500 base pairs. Based on the NGS results, the Stramenopiles-Alveolata-Rhizaria (SAR) was the most abundant group (90.10% and 80.16% of the total analysed read counts of 2013 and 2014, respectively). The Alveolata in the SAR group represented the most dominant subgroup&#8212 within Alveolata, however, the Dinophyta was the most abundant subgroup (90.39% and 77.25% for 2013 and 2014, respectively). Identified species in the Dinophyta totalled 32 taxa consisting of 17 genera, 29 species, and 3 unidentified organisms. The common taxa, Pentapharsodinium tyrrhenicum, Alexandrium tamarense, Alexandrium andersonii, Gonyaulax spinifera, Gymnodinium aureolum, and Woloszynskia cincta, were the predominant species. These results represent the first 52 sites, in December 2013) and a red tide summer (44 sites, in September 2014). The surface sediment samples were stored at 4 °C in a dark refrigerator for at least 6 months to allow decomposition of organic matter (such as living phytoplankton). The NGS analysis revealed 5,270&#8211 13,979 read counts and 175&#8211 273 operational taxonomic units (OTUs) with 97% sequence similarity obtained after quality filtering that included the selection of >500 base pairs. Based on the NGS results, the Stramenopiles-Alveolata-Rhizaria (SAR) was the most abundant group (90.10% and 80.16% of the total analysed read counts of 2013 and 2014, respectively). The Alveolata in the SAR group represented the most dominant subgroup&#8212 within Alveolata, however, the Dinophyta was the most abundant subgroup (90.39% and 77.25% for 2013 and 2014, respectively). Identified species in the Dinophyta totalled 32 taxa consisting of 17 genera, 29 species, and 3 unidentified organisms. The common taxa, Pentapharsodinium tyrrhenicum, Alexandrium tamarense, Alexandrium andersonii, Gonyaulax spinifera, Gymnodinium aureolum, and Woloszynskia cincta, were the predominant species. These results represent the first