Infection of phytoplankton by viruses and reduction of primary productivity

Abstract

NATURAL marine waters contain roughly 10⁶ to 10⁹ virus particles per ml, yet their role in aquatic ecosystems and the organisms that they infect remain largely unknown. Electron microscopy has been used to study interactions between viruses and their hosts, focusing mainly on pathogens to prokaryotic organisms^1–5. Here we demonstrate that viral pathogens infect a variety of important marine primary producers, including diatoms, cryptophytes, prasinophytes and chroococcoid cyanobacteria. Also, addition to sea water of particles in the 0.002–0.2 μm size range, concentrated from sea water by ultrafiltration, reduced primary productivity ([¹⁴C]bicarbonate incorporation) by as much as 78%. These results indicate that, in addition to grazing and nutrient limitation, infection by viruses could be a factor regulating phytoplankton community structure and primary productivity in the oceans.