Diel And Tidal Dynamics Of Marine Virus-host Interactions

Viruses are key players in marine ecosystem not only because they are the most.abundant and diverse biological entities but also they are the nanoscale drivers in the global biogeochemical cycle.The dynamics of the virus-host interactions will cause the switching of viral lytic and lysogenic infection,as well as the viral decay rate.Moreover,the dynamics of the virus-host interactions are able to affect the material circulation and energy flowing in marine microbial loop.However,the short-term dynamics of virus-host interactions over a diel and a tidal cycle are far less understood.To access the diel and tidal patterns of viral infection and decay facing the changing environmental and biotic parameters,we conducted the time series studies in the South China Sea and Jiulong estuary,Xiamen respectively.The main conclusions include:In the South China Sea,there were no obvious diel change of viral infection and decay rate blow the euphotic layer,but distinct diel patterns were detected in the surface and sub-surface.The frequency of viral lytic infection(FIC)was generally higher during the night but lower at the daytime in the surface,and FIC in the sub-surface showed an oppositely pattern.Surface FIC at oceanic station SEATS and offshore station J4 reached the peak on 02:00(4.59%and 10.46%,respectively);Sub-surface FIC at SEATS had a maximum at 18:00(5.44%)but a minimum at 02:00(1.16%).This difference mainly caused by the viral infection in the surface under the control of sunlight than host activities,but viral infection in the sub-surface just be affected by the host's activities.In addition,the stronger mixing at the offshore masked the diel change of viral infection.Furthermore,we found a positive relationship between the viral lytic and lysogenic infection over the diel cycle.The diel changes of environmental and biotic conditions leaded a significant dynamic viral decay.In this study,the virus-host interactions showed a diel pattern indicated that viruses can affect the microbial community composition and the marine biogeochemical cycle at a short time scale.A significant tidal pattern of microbial abundances was detected in Jiulong estuary,the higher abundances were generally found at high tide.The tidal dynamics caused a distinct change of frequency of viral lytic infection.FIC varied from 3.30 to 22.42%at the estuary station S03,1.5 to 6.04%and 0.42 to 4.01%at the distant station S05 and S07,respectively.The tidal mixing of freshwater and seawater as well as the changing salinity also caused the switching of viral infection strategies.The low salinity leaded a higher frequency of lysogenic infection and viral decay rate.Moreover,we found a positive relationship between the viral lytic and lysogenic infection over the tidal cycle.Our results showed that the tidal mixing and changing salinity caused the pattern of tidal virus-host interactions and the trade-off of viral strategies,which in turn affect the microbial activities and ecological functions in the estuary.