This dissertation represents a culmination of field work, computational analyses, and laboratory experiments investigating the virome of echinoderms with a particular focus on densoviruses that infect sea stars. The field work was conducted primarily on the East and West coasts of the United States in a collaborative effort to sample sea star tissues from a variety of species across a large geographical range. The tissue samples collected were used for viral analysis to uncover the diversity of viruses associated with sea stars, assess their tissue tropism, and document their biogeography. The computational analyses were performed on metagenomic data generated for this thesis and publicly available transcriptomic data for viral discovery, and the laboratory experiments are an ongoing effort to build an animal model system for culturing marine invertebrate viruses and testing their pathogenicity. These approaches were taken to pair observed patterns of infection in the field with an experimental model to understand the impacts of viral infection at the cellular and whole-animal scale. This work was conducted to (1) examine hypotheses related to the association of a densovirus, SSaDV, with Sea Star Wasting Syndrome (SSWS) observed in the Northeast Pacific and Northwest Atlantic coasts, (2) document the diversity of RNA viruses associated with echinoderms, and (3) culture SSaDV to experimentally test the impacts of viral infection in echinoderms. Field-based surveys show that densoviruses are pervasive and genetically diverse in sea star populations which challenges the SSaDV viral etiology hypothesis. This hypothesis was further examined through a comprehensive survey of RNA viruses associated sea stars which did not result in any RNA virus strongly associated with diseased individuals. In addition to the improved understanding of viral-host ecology and echinoderm viral diversity, this dissertation includes a demonstration of a plasmid-based reverse genetics approach to culture viruses in sea urchin embryos. This approach was taken using a plasmid clone of SSaDV to test the permissibility of sea urchin embryos and validate the biological function and infectivity of the viral clone. Collectively, this work attempts to bridge the gap between in silico and in vivo approaches to study host-virus associations in marine invertebrates