Marine virus predation by non-host organisms

Viruses are the most abundant biological entities in marine environments, however, despite its potential ecological implications, little is known about virus removal by ambient non-host organisms. Here, we examined the effects of a variety of non-host organisms on the removal of viruses. The marine algal virus PgV-07T (infective to Phaeocystis globosa) can be discriminated from bacteriophages using flow cytometry, facilitating its use as a representative model system. Of all the non-host organisms tested, anemones, polychaete larvae, sea squirts, crabs, cockles, oysters and sponges significantly reduced viral abundance. The latter four species reduced viral abundance the most, by 90, 43, 12 and 98% over 24 h, respectively. Breadcrumb sponges instantly removed viruses at high rates (176 mL h−1 g tissue dry wt−1) which continued over an extended period of time. The variety of non-host organisms capable of reducing viral abundance highlights that viral loss by ambient organisms is an overlooked avenue of viral ecology. Moreover, our finding that temperate sponges have the huge potential for constant and effective removal of viruses from the water column demonstrates that natural viral loss has, thus far, been underestimated.