16S library from the picoplankton fraction of surface seawater
Prefiltered surface seawater was successively filtered through membrane filters of decreasing pore sizes (20, 10, 5 and 0.22 µm) to separate the different cell size fractions. The picoplankton was therefore immobilized onto the 0.22 µm membranes. The picoplankton DNA was extracted from the 0.22 µm filters and 16S sequences were amplified using universal primers 27F and 1492R and pyrosequenced with barcode-tagged 27F primer.