Viruses in the sea:
Distribution, dynamics, and consequences

Grieg Steward, Ph.D.
Monterey Bay Aquarium Research Institute

Friday, March 26, 1999
12:00 Noon—Pacific Forum
(Video Conference to UC Berkeley)

The oceans are teeming with viruses. These smallest of the microbes are numerically dominant in every oceanic environment from the surface all the way into the sediments. A liter of surface seawater from Monterey Bay typically contains 25 billion of them, twenty times more than the bacteria in the same volume. In addition to being abundant, it is now believed that these obligate, intracellular parasites are a major source of mortality for bacteria and, at least occasionally, for other planktonic organisms as well. It was once thought that consumption by protozoa was the predominant fate of bacteria in the ocean, but recent evidence suggests that lysis by viruses is comparable. This revelation is forcing a revision of conceptual and numerical models of carbon flow in marine food webs. In addition to acting as executioners, viruses can also cause non-lethal infections which influence the physiology or evolution of their hosts. Whether an infection is lethal or non-lethal, viruses typically target their hosts quite specifically. Therefore, understanding their genetic diversity will be essential to appreciate the ways in which viruses shape marine communities. Although the counting of viruses is now routine, we are only just beginning to reveal the complexity within marine viral assemblages.

In this talk I will summarize some of the major themes which have emerged from the past decade of research in marine viral ecology and describe some of the current efforts being made to characterize the dynamics and diversity of viruses in the sea.

Next: Reconstructing ocean circulation using coral 14C time series