Discovery of urchin-associated densoviruses (family Parvoviridae) in coastal waters of the Big Island, Hawaii. Echinoderms are important constituents of marine ecosystems, where they may influence the recruitment success of benthic flora and fauna, and are important consumers of detritus and plant materials. There are currently no described viruses of echinoderms. We used a viral metagenomic approach to examine viral consortia within three urchins - Colobocentrotus atratus, Tripneustes gratilla and Echinometra mathaei - which are common constituents of reef communities in the Hawaiian archipelago. Metagenomic libraries revealed the presence of bacteriophages and densoviruses (family Parvoviridae) in tissues of all three urchins. Densoviruses are known typically to infect terrestrial and aquatic arthropods. Urchin-associated densoviruses were detected by quantitative PCR in all tissues tested, and were also detected in filtered suspended matter (>0.2 µm) from plankton and in sediments at several locations near to where the urchins were collected for metagenomic analysis. To the best of our knowledge, this is the first report of echinoderm-associated viruses, which extends the known host range of parvoviruses.