title: Metagenomic sequencing library of seawater from Yap trench: Yap500
design: The seawater sample was collected at Yap trench region by CTD SBE911plus (Sea-Bird Electronics) during the 37th Dayang cruise (4 June 2016 to 12 July 2016). Seawater (8 l per sample) was filtered through a 0.22-m-mesh membrane filter immediately after recovery, on board. The membrane was then cut into approximately 0.2-cm2 pieces with flame-sterilized scissors and added to a PowerBead Tube (MO BIO) and the subsequent steps were implemented according to the manufacturers protocol to extract DNA. The DNA was amplified in five separate reactions using REPLI-g Single Cell Kits (Qiagen) following the manufacturers protocol, given the challenging nature of sample retrieval and DNA recovery. The products were pooled and purified using QIAamp DNA Mini Kit (Qiagen) according to the manufacturers recommendations. Parallel blank controls were set for sampling, DNA extraction and amplification with 0.22-m-mesh membrane filtering Milli-Q water (18.2 M; Millipore)