The Environmental Sample Processor (ESP) filtered seawater sequentially through 5.0 um and 0.2 um pore size polyvinylidene fluoride filters. Seawater was evacuated from filters and followed twice with a 2 minute incubation with 1 ml of RNAlater™. RNAlater was evacuated, and filters were stored in the ESP until they were transferred to -80 C upon instrument recovery. 

Grab samples for sequencing while the ESP was not deployed were taken using Niskin bottles that collected seawater at the same depth and location of the ESP. Water was transferred to a low-density polyethylene cubitainer and maintained at ambient temperature until return to lab within 30 min. Seawater was filtered as above with vacuum filtration and preserved immediately in liquid nitrogen and transferred to -80 C.

Single-cell sequencing: Seawater was transferred directly from the Niskin bottle to a 50 ml Falcon tube and placed on ice until brought back to lab. Each sampling day, 3 x 1 ml of seawater was preserved in cryovials using 100 ul of glyTe (5 ml glycerol, 3 ml Milli-Q H2O, 1 ml 100 x TE pH 8.0, 0.2 um filter sterilized after mixing the above, and stored in -20 C freezer). Preserved samples were then placed in a -80 C freezer. Samples were processed and sequenced at JGI