Metavirome Insights into the Diversity and Potential Pathogenic Infection of Chlamys farreri in the Coastal Seas of the Republic of Korea

<i>Chlamys farreri</i> is primarily cultivated in Japan, China, and South Korea. Although mass mortality of scallops has been occurring recently, likely caused by high temperatures or infectious diseases, the underlying cause remains unclear. Little is known regarding the viral diseases affecting them. Therefore, we explored DNA virus diversity in the mid-gut gland of <i>C. farreri</i> and compared it with that of seawater. <i>C. farreri</i> was cultivated at depths below 5 m from the sea surface in the coastal waters of South Korea and sampled from May to August 2018. Different DNA viral communities were observed in both <i>C. farreri</i> and seawater. In <i>C. farreri</i>, prevalent groups included <i>Mimiviridae</i> (7%), <i>Poxviridae</i> (6%), and <i>Phycodnaviridae</i> (5%). Conversely, the dominant groups in seawater were <i>Autographiviridae</i> (20%), <i>Kyanoviridae</i> (12%), and <i>Zobellviridae</i> (10%). We identified <i>C. farreri</i>-specific viral communities and potentially infectious viruses, such as <i>Ostreid herpesvirus 1</i> and Abalone herpesvirus Victoria/AUS/2009. Furthermore, <i>C. farreri</i> acts as a reservoir for various viruses, which impact microbial community dynamics and disease transmission in marine ecosystems. Understanding these viral communities is crucial to protecting and restoring coastal ecosystems by highlighting their role in the transmission of potential avian- and bivalve-specific viruses.