Knowledge and implications of global change in the oceans for biology, ecology, and ecosystem services - Ocean Sustainability in the 21st Century - page 145

4.4 Effects of climate change on viruses and prokaryotes
The effects of global change will likely influence all ecosystem components and a broad
range of organisms including bacteria, Archaea, and Protista with diverse geographical dis-
tributions (Walther et al., 2001 ; Genner et al., 2004 ) . Viruses are the most numerous 'life-
forms' in aquatic systems (Suttle, 2005 ; 2007 ), numbering about 15 times the total numbers
of bacteria and Archaea. Recent studies revealed that viruses play a key role in deep-sea
metabolism and in global biogeochemical cycles (Danovaro et al., 2008b ) . Given that the
vast majority of the biomass OC in oceans consists of microorganisms, it is expected that
viruses and other prokaryotic and eukaryotic microorganisms will play important roles as
agents and recipients of global climate change. As viral replication and life cycle are closely
linked with host metabolism, increases in temperature will likely influence the interactions
between viruses and the cells they infect (Danovaro et al., 2011 ) . Recent analysis carried
out on a global scale reveals that the fraction of the total variance explained by the rela-
tionship between temperature and viruses is generally low, indicating that factors influen-
cing virioplankton distribution are more complex than those predicted by temperature alone
(Danovaro et al., 2011 ). Viruses have the potential to interact with the climate through their
contribution to the marine biogenic particles of the aerosol and by contributing to the re-
lease of DMS through lysis of their autotrophic hosts. These processes have to be quantified
and included in modelling studies dealing with ocean-atmosphere interactions. The oxygen
minimum zones are predicted to expand in the future ocean because of climate change, with
important consequences for biogeochemical cycling of nitrogen and phosphorus and for the
distribution of organisms. Because eukaryotic herbivores and bacterivores are more sensit-
ive than prokaryotes to the reduction in oxygen levels, it can be expected that virus-induced
mortality of prokaryotes will increase at the expense of protists and other bacterivores. The
effects of ocean acidification on marine viruses are uncertain, but we can anticipate that
the most dramatic changes will be due to the effects of pH on the host organisms that the
viruses rely on, bacteria, Archaea, protists, and metazoa, which are highly pH dependent.