Multi-domain temporal patterns reveal stable community membership but dynamic interactions in the coastal microbiome

Marine microbial communities drive global biogeochemical cycles and oceanic food webs, yet our understanding of their holistic temporal dynamics remains limited, particularly in the South China Sea. Most studies have focused on specific taxonomic groups or single temporal scales, leaving a gap in comprehensive, multi-domain, and multi-timescale analyses.

Using an integrated multi-omics approach that combined metagenomic, metatranscriptomic, and metaviromic analyses, we conducted time-series sampling over 48-h periods during winter and summer to investigate microbial community dynamics in the coastal South China Sea. Seasonal transitions were identified as the primary drivers of community shifts, with diel variations playing a secondary role across all taxonomic domains. Within seasons, diel changes followed a progressive trajectory rather than recurring cyclic patterns. Eukaryotic communities exhibited the most pronounced temporal fluctuations, while prokaryotic and viral communities displayed remarkable stability. Unlike previous coastal studies, viral communities maintained high similarity between seasons, suggesting the presence of a persistent viral reservoir in this region. Gene expression analysis revealed dynamic population shifts in photosynthetic microorganisms, with Mamiellophyceae green algae and their associated Prasinovirus displaying pronounced seasonal and diel rhythmicity.

This study provides novel insights into the temporal dynamics of microbial communities and host-virus interactions in the South China Sea. The stability of viral communities, coupled with synchronised host-virus activities, highlights potential mechanisms supporting ecosystem resilience in this coastal region. These findings enhance our understanding of marine ecosystem processes and establish a robust framework for exploring microbial responses to environmental changes on both diel and seasonal scales.