Fig. 5. Diagram of key differences between surface and low-oxygen samples detected in this study. Total identified PFAMs, represented by the Euler diagram, were mostly ‘core’.

These also represent most of the total normalized abundance of identified PFAMs, as represented by the boxes. Of those AMGs that were predominantly found in the mixed layer samples, the most abundant were psbA/D and psbN, which are involved in photosynthesis, and GDCP which is involved in glycine synthesis. The most abundant core low-oxygen AMGs include spoVS and spoVG, involved in sporulation, and hisA/F which is involved in histidine synthesis. This supports the hypothesis that the dominant viral strategy in the ETNP surface mixed layer is to boost host metabolism to facilitate viral replication, whereas those in the oxycline and OMZ are more likely to facilitate host persistence long enough for viral replication to occur.