The viral shunt in a stratified Northeast Atlantic Ocean
Mojica, K.D.A.; Brussaard, C.P.D. (2015). The viral shunt in a stratified Northeast Atlantic Ocean, in: Mojica, K.D.A. Viral lysis of marine microbes in relation to vertical stratification. pp. 207-222
In: Mojica, K.D.A. (2015). Viral lysis of marine microbes in relation to vertical stratification. PhD Thesis. Universiteit van Amsterdam: Amsterdam. ISBN 978-94-91407-20-8. 247 pp. hdl.handle.net/11245/1.487499, more
The flux of photosynthetic carbon (C) through the viral shunt affects nutrient cycling, system respiration, and food web dynamics. Yet, little is known about large-scale biogeographical patterns in the functioning of the viral shunt in marine systems. In the summer of 2009, we examined both the production and loss rates (i.e., grazing and viral lysis) of autotrophic as well as prokaryotic microbial populations along a north-south latitudinal gradient in the Northeast Atlantic Ocean. The upper water column located between 30 and 63°N was characterized by a strong temperature-induced vertical stratification, with oligotrophic regions extending to 45°N. Here we present the flow of C through the different components of the microbial food web in order to consider how these latitudinal changes affected the overall role of the viral shunt. Our results demonstrate that 33 and 80% of the photosynthetically fixed C moved through the viral shunt into the dead particulate and dissolved matter pool in the north and south, respectively, indicating a more prominent role of viruses in marine nutrient cycles than theorized previously by Wilhelm and Suttle in 1999. The flux of C was reduced 2-fold in the north, as a consequence of lower viral-induced morality of both phytoplankton and bacteria. Our results suggest that future shifts in the regional climate of the ocean surface layer are likely to increase the role of the viral shunt in marine microbial food webs, which may reduce the transfer of matter and energy up the food chain and thus affect the capacity of the North Atlantic to act as a long-term sink for CO2.
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