Water phase of unfiltered seawater
Samples were filtered through 0.2 µm Sterivex polyvinylidene fluoride (PVDF) filters (Millipore, Billerica, MA, USA) and extracted by hot phenol-chloroform-isoamylalcohol extraction. Genomic DNA was fragmented by sonication (Covaris™ S220 Sonicator; Covaris, Inc., Woburn, MA) to approximately 300 base pairs (bp), and fragments used to synthesize indexed sequencing libraries using the TruSeq DNA Sample Prep Kit V2 (Illumina, Inc., San Diego, CA), according to manufacturer’s recommended protocol.  Cluster generation was performed on the cBOT using the TruSeq PE Cluster Kit v3 – cBot – HS (Illumina).  Libraries were sequenced with an Illumina HiSeq 2000 using the TruSeq SBS Kit v3 reagents (Illumina) for paired end sequencing with read lengths of 100 bp (200 cycles).