Algal viruses and cyanophages have distinct distributions in Lake Erie sediments

Algal viruses and cyanophages infect primary producers and have wide-ranging effects upon the food web and biogeochemical cycles. However, little is known about the diversity and distribution of these viruses in freshwater sediments. To address this information gap, sediment core samples were collected from Lake Erie at 4 distinct sites across its 3 basins. PCR primers targeting porn gene sequences of phycodnaviruses and viral capsid assembly genes (g20) of cyanomyoviruses were used to examine the diversity of viral sequences. Additionally, quantitative PCR primers and probes were used to estimate the abundances of algal virus and cyanophage genes at each location. PCR and sequencing of porn and g20 genes revealed diverse assemblages of putative phycodnaviruses and cyanomyoviruses, uncovering novel viral gene sequences and some related to virus genes observed previously in water column samples. Wide abundance ranges of 11 different algal virus (from below detection to 1.43 x 10(6) gene copies per gram wet sediment) and cyanophage (from below detection to 2.39 x 10(4) gene copies per gram wet sediment) genes were detected using quantitative PCR. Abundance patterns were spatially variable and distinct for different virus genes. Algal viruses tended to be more abundant in the central and eastern basins, while cyanophages tended to be more abundant in the western basin. The observed diversity of viruses, coupled with the high abundances of several virus genes, suggests that aquatic sediments are an important environmental refugium for phytoplankton viruses and that their geographic patterns may reflect local host abundances.