Genome-resolved viral ecology in a marine oxygen minimum zone (OMZ).

Oxygen minimum zones (OMZs) are critical to marine nitrogen cycling and global climate change. While OMZ microbial communities are relatively well-studied, little is known about their viruses. Here we assess the viral community ecology of 22 deeply sequenced viral metagenomes along a gradient of oxygenated to anoxic waters (< 0.02 μmol/L O2 ) in the Eastern Tropical South Pacific (ETSP) OMZ. We identified 46,127 viral populations (≥ 5 kb), which augments the known viruses from ETSP by 10-fold. Viral communities clustered into 6 groups that correspond to oceanographic features. Oxygen concentration was the predominant environmental feature driving viral community structure. Alpha and beta diversity of viral communities in the anoxic zone were lower than in surface waters, which parallels the low microbial diversity seen in other studies. ETSP viruses were largely endemic, with the majority of shared viruses (87%) also present in other OMZ samples. We detected 543 putative viral-encoded auxiliary metabolic genes (AMGs), of which some have a distribution that reflects physio-chemical characteristics across depth. Together these findings provide an ecological baseline for viral community structure, drivers and population variability in OMZs that will help future studies assess the role of viruses in these climate-critical environments. This article is protected by copyright. All rights reserved.