title: Viruses and the microbial loop.
abstract: The abundance of viral-like particles in marine ecosystems ranges from <104 ml(-1) to >10(8) ml(-1). Their distribution in time and space parallels that of other biological parameters such as bacterial abundance and chlorophyll a. There is a lack of consensus between methods used to assess viral activity, i.e., rate of change in viral abundance (increase or decrease). The highest rates, 10-100 days(-1), are observed in experiments with short sampling intervals (0.2-2 h), while lower rates, on the order of 1 day(-1), are observed in experiments with longer sampling intervals (days). Few studies have been carried out, but viruses appear, at least in some cases, to have a significant impact on carbon and nutrient flow in microbial food webs. Viruses have also been demonstrated to exert a species specific control of both bacteria and phytoplankton populations in natural waters.
authors.affiliation: Department of Microbiology, University of Bergen, Jahnebakken 5, N-5020, Bergen, Norway.
authors.forename: G
authors.initials: G
authors.lastname: Bratbak
authors.forename: F
authors.initials: F
authors.lastname: Thingstad
authors.forename: M
authors.initials: M
authors.lastname: Heldal