Seawater was collected from surface to abyssopelagic zone throughout a year at St. S1 (30N, 145E) in 2010-2011. Samples for DNA analysis from each depth were sequentially size fractionated through a 3 um pholycabonate filters (Whatman, Maidstone, UK) followed by filtration onto a 0.2 um Millipore Sterivex filter unit (EMD Milipore, Dermstadt, Germany). The filter samples were frozen immediately and stored at -80 ?C until onshore analysis. Total DNA was extracted and partial 18S rRNA gene of eukaryotes was amplified and sequenced using Illumina Miseq.