Targeted and comparative viral community genomics of the Eastern North Pacific

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Two climatically and biogeochemically important features characterize the Eastern North Pacific (ENP). This region encompasses one of the planet's largest oxygen minimum zones, and annually hosts a phytoplankton bloom that leads to some of the highest dimethyl sulfide (DMS) concentrations observed. Oxygen minimum zones (OMZs) play integral roles in marine biogeochemical cycles, as major sinks for nitrogen and sources for climatologically active trace gases including methane and nitrous oxide. There is increasing evidence that projected ocean warming and circulation changes is decreasing dissolved oxygen concentrations within the coastal and interior regions of the ENP, causing lateral and vertical OMZ expansion. This will have a direct effect on coastal benthic ecosystems and the productivity of marine fisheries, as well as potentially positive climatalogical feedbacks. In addition, the DMS produced in the ENP is a potential negative feedback for atmospheric warming through its role in atmospheric cloud formation, while it also accounts for approximately half of the planet's total biogenic sulfur flux. The PI of this project has collaborated with Dr. Steven Hallam (UBC) since June 2008 to archive viral community DNA, paired with high molecular weight genomic DNA from microbial biomass (since June 2006) and a rich synoptic oceanographic metadataset, along defined redox gradients in the ENP as part of the Canadian-funded Line P time series program. The viral samples focus on open-ocean station OSP and span surface waters, hypoxic interior, and upper and lower oxichypoxic transition zones. Microbial investigations, ongoing since 2006, have examined community diversity and population structure of indigenous microbial groups in the ENP. Time-series analyses have revealed dynamic seasonal changes, consistent with changing light, temperature, and nutrient conditions. However, little is known about the role that co-occurring viral communities play in modulating microbial community dynamics and responses to both water column hypoxia and massive DMS production and sulfur cycling. Marine viruses are responsible for the largest flux of carbon in the oceans by lysing microbial cells, while also encoding "host" metabolic genes. In the case of marine cyanobacteria, phage directly impact global carbon cycling by encoding ~60% of the core reaction center genes in surface water photosystems. Understanding coupled viral, microbiological and biogeochemical processes the ENP is critical to understand, predict, or one day possibly mitigate changes in productivity and trace gas cycling associated with OMZ expansion and changing DMS production. This project will investigate viral community diversity and metabolic capacity through viral metagenomes sampled along defined spatiotemporal gradients in the ENP. The endeavor is highly leveraged with funding already secured for sequencing 20 viral metagenomes, and their co-occurring microbial communities at high phylogenetic resolution using 16S hypervariable sequence tagging through the DOE JGI Community Sequencing Program and the Moore Foundation viral sequencing initiative. This project will identify relevant patterns of viral-host interaction with profound ecological and evolutionary consequences.Broader impacts: The microbial and viral sampling effort will be performed by post-docs and graduate students in the context of a 50+ year oceanographic sampling effort that allows these trainees see the vast biogeochemical and physical oceanographic measurements required to "survey" an ocean community. This project will expose undergraduates and high school students to the excitement of field-based oceanographic research through a combination of direct involvement in research, a Biosphere 2 "hands-on sampling training", and a new course at Tucson High School entitled "Ocean viruses: From isolates to genomes and metagenomes".