MEPS 494:65-72 (2013)  -  DOI: https://doi.org/10.3354/meps10575

ABSTRACT: Circular replication initiator protein (rep)-encoding ssDNA (CRESS-DNA) viruses have been widely reported in viral metagenomic surveys and in association with invertebrate zooplankton in freshwater and marine habitats. However, there have been no systematic or quantitative studies of their distribution in marine waters. We investigated the distribution of CRESS-DNA viruses in net plankton (>64 µm) collected from geographically widespread locations, using quantitative PCR that targets viral genotypes previously recovered from soil, freshwater and estuarine free-living viruses, and viruses associated with arthropod tissues. We detected CRESS-DNA viruses in most net plankton samples except for a sample containing only the cyanobacterium Trichodesmium. Soil and freshwater plankton CRESS-DNA viruses were detected only at sites with substantial freshwater and runoff effects, while 2 CRESS-DNA viruses recovered from plankton of the Chesapeake Bay were detected in most net plankton tested. CRESS-DNA viruses recovered from marine copepods, the freshwater cladoceran Daphnia and the freshwater amphipod Diporeia were primarily detected in habitats where similar hosts were observed in zooplankton counts. Our data suggest that CRESS-DNA viruses previously recovered from invertebrate tissues and from virioplankton may be widely distributed in plankton >64 µm, providing evidence for a zooplankton origin of this viral group.

KEY WORDS: Virioplankton · Circovirus · Zooplankton · Copepods · Amphipods · Daphnia