Background/Question/Methods While our understanding of the ecology of viruses in planktonic marine systems has expanded over the past 2 decades, research into the role of viruses in freshwater systems lags well behind. In marine environments, the role of viruses as regulators of carbon and nutrient recycling as well as microbial community structure has been a focus of numerous labs, yet in freshwater the role of viruses in biogeochemical cycles remains largely unstudied. Recent data from virus production assays suggest that viruses play an equally important role in large lake biogeochemical cycles, particularly as drivers of organic-P regeneration. The application of innovative molecular approaches by marine microbial ecologists has further provided significant insight into the diversity of specific viral populations that researchers are just beginning to explore in freshwater ecosystems.

Results/Conclusions .   New data on the molecular diversity and activity of viruses in freshwaters not only suggests that marine and freshwater viruses are genetically related and in similar ecological niches, but that viruses in marine and freshwater systems have become differentiated enough to be phylogenetically resolved using new molecular tools. Combined with insights on the role of viruses in biogeochemical cycles, the  observations to be discussed highlite the importance of including viruses in aquatic  food web models.