Project: Unraveling the Ecological and Evolutionary Drivers of Marine Giant Virus Community Dynamics

Viruses are key players in modulating marine biogeochemical processes and populations of numerous microorganisms. Nucleocytoplasmic Large DNA Viruses (NCLDVs), commonly known as ‘giant viruses’, have garnered increased attention given their remarkable phylogenomic and functional diversity in the ocean. NCLDVs infect microbial eukaryotes (protists) with diverse life-strategies, highlighting their multifaceted role within the microbial food web. Despite significant advances in cataloging NCLDV diversity, the ecological drivers and evolutionary mechanisms shaping their community dynamics remain poorly understood. This study aims to elucidate the ecological and evolutionary determinants of marine NCLDV community structure through a comprehensive, year-long time-series analysis at a model coastal site, Quantuck Bay, NY. This research will consider a range of drivers that include extrinsic, abiotic factors; and intrinsic factors shaped by evolutionary processes - such as phylogenetic and functional diversity, host range and ecological strategies. Genome-resolved metagenomics over a year-long period will be employed to comprehensively map out the genomic diversity and metabolic capacities of NCLDVs. Next, using high-temporal resolution sampling of metagenomics and metatranscriptomics over three months, we will evaluate how NCLDV ecological strategies underpinning the observed community composition and dynamics vary across the phylogeny. Concurrently, we will assess how abiotic factors like nutrients shape the abundance and activity dynamics of the NCLDV lineages. Finally, host associations of the NCLDVs will be revealed using co-occurrence networks and genomic signatures. This research will provide critical insights into the ecological roles of NCLDVs in marine systems and their potential responses to environmental changes, with implications for marine biogeochemical cycles and food web processes.