title: Oxygen minimum zones harbour novel viral communities with low diversity.
abstract: Oxygen minimum zones (OMZs) are oceanographic features that affect ocean productivity and biodiversity, and contribute to ocean nitrogen loss and greenhouse gas emissions. Here we describe the viral communities associated with the Eastern Tropical South Pacific (ETSP) OMZ off Iquique, Chile for the first time through abundance estimates and viral metagenomic analysis. The viral-to-microbial ratio (VMR) in the ETSP OMZ fluctuated in the oxycline and declined in the anoxic core to below one on several occasions. The number of viral genotypes (unique genomes as defined by sequence assembly) ranged from 2040 at the surface to 98 in the oxycline, which is the lowest viral diversity recorded to date in the ocean. Within the ETSP OMZ viromes, only 4.95% of genotypes were shared between surface and anoxic core viromes using reciprocal BLASTn sequence comparison. ETSP virome comparison with surface marine viromes (Sargasso Sea, Gulf of Mexico, Kingman Reef, Chesapeake Bay) revealed a dissimilarity of ETSP OMZ viruses to those from other oceanic regions. From the 1.4 million non-redundant DNA sequences sampled within the altered oxygen conditions of the ETSP OMZ, more than 97.8% were novel. Of the average 3.2% of sequences that showed similarity to the SEED non-redundant database, phage sequences dominated the surface viromes, eukaryotic virus sequences dominated the oxycline viromes, and phage sequences dominated the anoxic core viromes. The viral community of the ETSP OMZ was characterized by fluctuations in abundance, taxa and diversity across the oxygen gradient. The ecological significance of these changes was difficult to predict; however, it appears that the reduction in oxygen coincides with an increased shedding of eukaryotic viruses in the oxycline, and a shift to unique viral genotypes in the anoxic core.
authors.affiliation: Department of Biology, San Diego State University, San Diego, CA 92182, USA.
authors.forename: Noriko
authors.initials: N
authors.lastname: Cassman
authors.forename: Alejandra
authors.initials: A
authors.lastname: Prieto-Davó
authors.forename: Kevin
authors.initials: K
authors.lastname: Walsh
authors.forename: Genivaldo G Z
authors.initials: GG
authors.lastname: Silva
authors.forename: Florent
authors.initials: F
authors.lastname: Angly
authors.forename: Sajia
authors.initials: S
authors.lastname: Akhter
authors.forename: Katie
authors.initials: K
authors.lastname: Barott
authors.forename: Julia
authors.initials: J
authors.lastname: Busch
authors.forename: Tracey
authors.initials: T
authors.lastname: McDole
authors.forename: J Matthew
authors.initials: JM
authors.lastname: Haggerty
authors.forename: Dana
authors.initials: D
authors.lastname: Willner
authors.forename: Gadiel
authors.initials: G
authors.lastname: Alarcón
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Ulloa
authors.forename: Edward F
authors.initials: EF
authors.lastname: DeLong
authors.forename: Bas E
authors.initials: BE
authors.lastname: Dutilh
authors.forename: Forest
authors.initials: F
authors.lastname: Rohwer
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Dinsdale
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000145:classification / Q000235:genetics; D001435:Bacteriophages / Q000235:genetics / Q000502:physiology; D044822:Biodiversity; D002677:Chile; D005838:Genotype; D009584:Nitrogen / Q000378:metabolism; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010802:Phylogeny; D012623:Seawater / Q000821:virology*; D013455:Sulfur / Q000378:metabolism; D018406:Virus Physiological Phenomena; D014780:Viruses / Q000235:genetics
chemical_list: D013455:Sulfur; D009584:Nitrogen; D010100:Oxygen