Dr Satoshi Nagai

Dr Satoshi Nagai

National Research Institute of Fisheries Science,Japan

Title: Plankton metagenomics in Okhotsk Sea in Japan


Satoshi Nagai has completed his PhD at the age of 29 years from Kyoto University, and started to work as a permanent resercher at Fisheries Research Agency of Japan. He is the group leader of metagenome research group at the research center for aquatic genomics. He has published more than 110 papers in reputed journals and has been serving as an editorial board member of Plankton & Benthos Research and BMC genomics


We have conducted a monitoring of eukaryote biodiversity by using massively parallel sequencing (MPS)-based technology one a week for nearly three years in Mombetsu city, Hokkaido, Japan. In this study, we analyzed the biodiversity of some samples (n = 32) as a preliminary study and succeeded in detecting several hundreds of operational taxonomic units (OTUs) from 500 mL seawaters. In the NMDS analysis, samples taken at the same month but in different dates were more closely plotted and also the samples of closest months were located in the closest positions, showing the consecutive transition of species composition and the clear seasonal pattern of eukaryote species in Okhotsk Sea. The relative abundance of identified OTUs at the supergroup levels at the four groups was compared. The relative abundance of Alveolata or Stramenopiles was highest, and the third highest groups were Opisthokonta, or Viridiplantae, which varied depending on the samples, and they accounted for 77.1-86.4% of the total. The relative abundance of Stramenopiles was 37.6% at Jan-Mar group and the highest among the groups, reflecting the conspicuous diatom spring blooms. The lowest water temperature during diatom spring blooms in Okhotsk Sea is nearly -2 oC, but 8-9 oC in the Seto Inland Sea. Diatom species isolated from western Japan cannot grow below 5 oC under laboratory conditions. The MPS-based technology also enabled to detect conspicuous diatom spring blooms and sudden blooms, which occurred irregularly, caused by dinoflagellate, ciliate or metazoa species, strongly suggesting the effectiveness of the monitoring by the MPS-based technology.