Viruses and Nutrient Cycles in the Sea: Viruses play critical roles in the structure and function of aquatic food webs

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Few of us may ever live on the sea or under it, but all of us are making increasing use of it either as a source of food and other materials, or as a dump. As our demands upon the ocean increase, so does our need to understand the ocean as an ecosystem. Basic to the understanding of any ecosystem is knowledge of its food web, through which energy and materials flow. (Pomeroy 1974, p. 499)

Viruses are typically viewed as pathogens that cause disease in animals and plants. In recent years, however, it has become increasingly clear that they play critical roles in the world's oceans. Of particular current interest is the influence of viruses on the cycling of nutrients and carbon in oceans. Viruses are abundant and dynamic members of marine systems (for reviews, see Borsheim 1993, Fuhrman and Suttle 1993, Bratbak et al. 1994), but they are sensitive to a variety of environmental stresses that can lead to their inactivation or destruction. It follows that maintaining abundant viral populations requires a high production rate of new viruses and the consequent destruction of a significant proportion of their natural hosts, primarily heterotrophic bacteria and phytoplankton.