Diversity, evolutionary contribution and ecological roles of aquatic viruses.

Aquatic viruses include infected viruses in aquatic animals, plants and microorganisms, and free-floating viruses (virioplankton) in water environments. In the last three decades, a huge number of aquatic viruses, especially diverse free-floating viruses, including cyanophages, phycoviruses, archaea viruses, giant viruses, and even virophages, have been identified by virological experiments and metagenomic analyses. Based on a comprehensive introduction of aquatic virus classification and their morphological and genetic diversity, here, we summarize and outline main virus species, their evolutionary contribution to aquatic communities through horizontal gene transfer, and their ecological roles for cyanobacterial bloom termination and global biogeochemical cycling in freshwater and marine ecosystems. Thereby, some novel insights of aquatic viruses and virus-host interactions, especially their evolutionary contribution and ecological rolesin diverse aquatic communities and ecosystems, are highlighted in this review.