Effects of ultraviolet radiation on marine virus–phytoplankton interactions

Abstract

Ambient ultraviolet radiation (UVR) is harmful to many biological systems and increased UVR, due to a reduced ozone layer, may have many unforeseen consequences. Viruses are the most abundant biological particles in the sea and are thought to play an important role in the structure and functioning of aquatic ecosystems. Although an increasing number of studies have been published during the last 15 years, aquatic viral ecology is still in its infancy and little is known about the effect of environmental factors on virus life cycle and host-virus interactions. Using flow cytometry, we have investigated the effect of UVR (UVB intensity: 0.22 W m(-2) and UVA/UVB ratio approximately 30) on five different cultured marine phytoplankton host-virus systems (CeV-Chrysochromulina ericina, EhV-Emiliania huxleyi, MpV-Micromonas pusilla, PpV-Phaeocystis pouchetii and PoV-Pyramimonas orientalis). Viruses appear to be susceptible to UV, but also they might provide some protection to their hosts. It is shown that (i) some of the investigated microalgae that have been co-cultured with viruses are less sensitive (e.g. P. pouchetii, M. pusilla) to UVB stress compared to susceptible microalgae (i.e. virus-free cultures), (ii) different viruses have different sensitivities to UVB in terms of both their abundance patterns (no effect for most of them except EhV) and infectivity (from no effect for PoV, to complete inactivation for PpV), (iii) UVA has no effect on host-virus interactions. Our results show UVB to be a potentially important factor in the regulation of virus-host interactions in surface waters.

Estimates of virus- vs. grazing induced mortality of picophytoplankton in the North Sea during summer

“…(5) The absence of viral lysis could be caused by a reduced viral infectivity. In the surface layer of the ocean environmental factors such as high solar radiation, and particularly UV radiation (UVR), can severely alter the infectivity of algal viruses (Cottrell & Suttle 1995, Garza & Suttle 1998, Jacquet & Bratbak 2003. It is noteworthy that viral lysis was detected exclusively in light attenuated environments in the present study.…”

Seasonal determinations of algal virus decay rates reveal overwintering in a temperate freshwater pond

“…Exposure to UV radiation and PAR can deactivate viruses (Cottrell and Suttle, 1995;Furuta et al, 1997;Jacquet and Bratbak, 2003;Baudoux et al, 2012), yet some algal viruses encode genetic machinery to repair light-induced DNA damage. Many, but not all, genomes of chloroviruses, including ATCV-1 and CVM-1, contain homologs of a UV repair gene, denV, which encodes a UV-specific DNA glycosylasepyrimidine lyase (Fitzgerald et al, 2007;Jeanniard et al, 2013) known to be functional in the strain PBCV-1 (Furuta et al, 1997).…”

Phaeocystis and its interaction with viruses

“…Ways of removal can include passive adsorption of viruses onto the abundant organic aggregates (TEP) that are grazed upon, or onto inorganic colloids (clay, sand) that are removed from the euphotic zone by sinking (Kapuscinski and Mitchell 1980;Brussaard et al 2005b). Other factors aVecting the loss of the virus particles or infectivity are grazing by protozoa, enzymatic hydrolysis, and UV radiation as it damages the viral nucleic acids (Kapuscinski and Mitchell 1980;Suttle and Chen 1992;González and Suttle 1993;Noble and Fuhrman 1997;Jacquet and Bratbak 2003). Despite the dynamic nature and the substantial losses of PgV, phenotypic characterization and molecular analysis of PgV isolates collected one year apart from the same area revealed identical sequences, indicating considerable stability of these PgV populations Baudoux and Brussaard 2005).…”

“…UV-B radiation strongly inhibited viral infectivity, whereas UV-A radiation had no eVect (Jacquet and Bratbak 2003). A fascinating additional Wnding was the reduced sensitivity to UV-B stress of P. pouchetii cells that previously escaped viral infection.…”