LAUSR

Table S1: 18S rRNA gene identity of the abundant ribotypes listed in Table 2 (main text). The reads are identified to the closest species match following a BLASTn search. Average percent of similarity of reads to the species, and functional category (Cat): Dinoflagellates (Dino); heterotrophic nanoflagellates (HNF); mixotrophic nanoflagellates (MNF), which are referred to as Nanoeuks in the main text; and photosynthetic picoplankton (PPP), which are referred to as Picoeuks in the main text. The Picozoa were the only heterotrophic pico flagellate (HPF) and the uncultivated alveolates that are classified as Syndinales groups were considered parasites (Para). The size and functional role of the Braarudosphaera-like OTU is uncertain.