Community connectivity and potential functions of viruses along the particle size spectrum in the twilight zone

Viruses are the most abundant biological entities that play essential roles in the biogeochemical cycling in ocean. However, their composition, function and connectivity associated with sinking particles in the twilight zone remain poorly understood. We recovered a total of 5,016 viral OTUs from multiple particle sizes at different depths across three regions, which exhibited high novelty and diversity. Surface small particles harboured more lytic viruses, while deeper large particles hosted more temperate viruses and unclassified taxa. Over 1,000 vOTUs were linked to prokaryotic hosts, mainly Proteobacteria. Metabolic annotation identified 178 auxiliary metabolic genes (AMGs)and 12 carbohydrate-active enzymes families, primarily in temperate Caudoviricetes, providingfunctional complementation in virus-host interactions. Extensive co-occurrence of vOTUs across water layers was revealed, with surface-originated viruses being transported via particles to the twilight zone and beyond. These findings provide new insights into the roles of viruses in carbon cycling and vertical connectivity in the ocean.