Can viral induced mortality be represented with a quadratic mortality function?

The impact of viral induced mortality of algal and bacterial cells on elemental flow has been poorly quantified. Biogeochemical modelers have avoided explicitly resolving viral infection by assuming that phytoplankton mortality increases quadratically with cell density. Using a water-column model with a nutrient-phytoplankton-zooplankton-virus-detritus (NPZVD) configuration including an infected phytoplankton class, we ask whether the quadratic mortality function captures patterns of viral induced mortality. The quadratic function underpredicts viral mortality during shallow mixing when phytoplankton biomass is highest, and overpredicts mortality during deep mixing and beneath the mixed layer when phytoplankton biomass is lowest. We interpret these findings to be associated with the time-delay that arises between initial infection and host lysis, that requires an explicit representation of infected cells. We present initial assessments of the magnitude of error associated with quadratic mortality on integrated primary production and carbon export and discuss the implications of our findings for large-scale models of ocean biogeochemistry.

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Primary Presenter: Eric Carr, University of Tennessee (ecarr@utk.edu)

Authors:

David Talmy, University of Tennessee  (dtalmy@utk.edu)

Stephanie Dutkiewicz, Massachusetts Institute of Technology  (stephdut@mit.edu)

Eric Carr, University of Tennessee  (ecarr@utk.edu)