Pathogens and Passengers: Roles for Crustacean Zooplankton Viruses in the Global Ocean

Abstract

Viruses infect all living organisms, but the viruses of most marine animals are largely unknown. Crustacean zooplankton are a functional lynchpin in marine food webs, but very few have been interrogated for their associated viruses despite the profound potential effects of viral infection. Nonetheless, it is clear that the diversity of viruses in crustacean zooplankton is enormous, including members of all realms of RNA viruses, as well as single- and double-stranded DNA viruses, in many cases representing deep branches of viral evolution. As there is clear evidence that many of these viruses infect and replicate in zooplankton species, we posit that viral infection is likely responsible for a significant portion of unexplained non-consumptive mortality in this group. In turn, this infection affects food webs and alters biogeochemical cycling. In addition to the direct impacts of infection, zooplankton can vector economically devastating viruses of finfish and other crustaceans. The dissemination of these viruses is facilitated by the movement of zooplankton vertically between epi- and mesopelagic communities through seasonal and diel vertical migration (DVM) and across long distances in ship ballast water. The large potential impact of viruses on crustacean zooplankton emphasises the need to clearly establish the relationships between specific viruses and the zooplankton they infect and investigate disease and mortality for these host–virus pairs. Such data will enable investigations into a link between viral infection and seasonal dynamics of host populations. We are only beginning to uncover the diversity and function of viruses associated with crustacean zooplankton.

Viruses of Plankton: On the Edge of the Viral Frontier

“…viruses to enter the food web (Figure1; blue arrows; viral loop), but also modifies our conception of trophic interactions within food webs [16,17]. The articles by Roberts and Suttle [9] and Al-Ameeli et al [13] expand upon our understanding of the myriad of ways in which viruses and zooplankton interact in aquatic environments (Figure 1; gray arrow and the viral loop). Metagenomics has advanced our understanding of virus diversity in aquatic systems and illuminated the mechanisms through which viruses interact with their hosts [18].…”

“…Viruses infect all living organisms, but in general, viruses infecting zooplankton are understudied [ 9 ]. This is primarily due to the scarcity of symptomatological studies of viral diseases in plankton and the absence of definitive links to host mortality in many marine species.…”

“…This is primarily due to the scarcity of symptomatological studies of viral diseases in plankton and the absence of definitive links to host mortality in many marine species. The review in this Special Issue by Roberts & Suttle [ 9 ] provides an overview of the current knowledge of viral pathogens of crustacean zooplankton and their effects on marine food webs. The authors establish the plausibility for viral infection to be responsible for a significant portion of unexplained non-consumptive mortality of crustacean zooplankton and the potential for these hosts to serve as vectors of disease.…”

“…Significant prevalence of virovory in aquatic environments not only alters our view of carbon flow through marine food webs by introducing a new pathway for viruses to enter the food web ( Figure 1 ; blue arrows; viral loop), but also modifies our conception of trophic interactions within food webs [ 16 , 17 ]. The articles by Roberts and Suttle [ 9 ] and Al-Ameeli et al [ 13 ] expand upon our understanding of the myriad of ways in which viruses and zooplankton interact in aquatic environments ( Figure 1 ; gray arrow and the viral loop).…”