Abstract: Microphytobenthos and sea ice algae comprise globally significant photosynthetic biofilms. While their microalgal and bacterial constituents are well characterized,there is very little information on their viral communities or on the virus-bacteria and virus-algae interactions within them. While high levels of interaction might be expected because of the high density of cells,infection rates,particularly of microalgae,have been found to be low. It remains unclear whether this is a result of environment characteristics,developed resistance or because of the small number of studies.