This study presents a genomic analysis of two uncultured marine viral communities, focusing on their diversity and composition. The researchers isolated viral DNA from surface seawater samples collected from Scripps Pier and Mission Bay, using differential filtration and density-dependent gradient centrifugation. They then constructed a linker-amplified shotgun library (LASL) to sequence the viral community DNA. Over 65% of the sequences were not similar to previously reported sequences, indicating significant uncharacterized diversity. The most common hits among known sequences were to viruses, including representatives from major families of dsDNA tailed phages and some algal viruses. Mathematical models based on the observed number of contigs predicted that the most abundant viral genome comprised 2-3% of the total population in both communities, with an estimated range of 374 to 7,114 viral types. The results highlight the extremely high diversity of marine viral communities and suggest that it is feasible to sequence the entire genome of an uncultured marine viral community.This study presents a genomic analysis of two uncultured marine viral communities, focusing on their diversity and composition. The researchers isolated viral DNA from surface seawater samples collected from Scripps Pier and Mission Bay, using differential filtration and density-dependent gradient centrifugation. They then constructed a linker-amplified shotgun library (LASL) to sequence the viral community DNA. Over 65% of the sequences were not similar to previously reported sequences, indicating significant uncharacterized diversity. The most common hits among known sequences were to viruses, including representatives from major families of dsDNA tailed phages and some algal viruses. Mathematical models based on the observed number of contigs predicted that the most abundant viral genome comprised 2-3% of the total population in both communities, with an estimated range of 374 to 7,114 viral types. The results highlight the extremely high diversity of marine viral communities and suggest that it is feasible to sequence the entire genome of an uncultured marine viral community.