18S rDNA amplicon of filtered sea water
The sea water was collected on surface and filtered. DNA from the filters was extracted with the DNeasy PowerWater kit (QIAGEN). DNA from each filter were amplified with the V4F (5'-CCA GCA SCY GCG GTA ATT CC-3 ') (Stoeck et al., 2010) and V4RB (5'-ACT TTC GTT CTT GT YRR-3') (modified by Balzano et al. 2015) universal primers targeting the V4 region of the 18S rDNA. Amplicon sequencing was carried out on Illumina MiSeq.