Rhythms of lysis: Viral regulation of prokaryotic turnover across diel cycles

Abstract Diel rhythms structure microbial activity in the ocean, yet the role of viral lysis in driving short‐term community dynamics remains poorly understood. Here, we combined dilution experiments, high‐resolution microbiome sampling and extracellular ribosome sequencing to investigate diel virus–host interactions in the South China Sea. Viral lysis accounted for an average of 41% of Synechococcus and 24% of heterotrophic bacterial mortality at night. Overall, 74% of amplicon sequence variants (ASVs) showed lysis signals, with many displaying significant diel fluctuations. Notably, rare taxa comprised a large fraction of diel‐responsive ASVs, indicating high turnover among low‐abundance populations. Synechococcales exhibited tightly coupled nighttime peaks in abundance and lysis, while SAR11 and Flavobacteriales showed delayed lysis after late‐day growth. In addition, virus‐mediated mortality had a stronger influence on metabolically active and diel‐responsive ASVs. These findings highlight viral lysis as a temporally structured and taxon‐specific force sustaining microbial turnover and diversity in oligotrophic waters.