Abstract
The encounter and capture of bacteria and phytoplankton by microbial predators and parasites is fundamental to marine ecosystem organization and activity. Here, we combined biophysical models with published laboratory measurements to infer functional traits, including encounter kernel and capture efficiency, for a wide range of marine viruses and microzooplankton grazers. Despite virus particles being orders of magnitude smaller than microzooplankton grazers, virus encounter kernels and adsorption rates were in many cases comparable in magnitude to grazer encounter kernel and clearance, pointing to Brownian motion as a highly effective method of transport for viruses. Inferred virus adsorption efficiency covered many orders of magnitude, but the median virus adsorption efficiency was between 5 to 25% depending on the assumed host swimming speed. Uncertainty on predator detection area and swimming speed prevented robust inference of grazer capture efficiency, but sensitivity analysis was used to identify bounds on unconstrained processes. These results provide a common functional trait framework for understanding marine host-virus and predator-prey interactions, and highlight the value of theory for interpreting measured life-history traits.
Highlights
Marine ecosystems include diverse microbial communities whose interactions mediate and drive biogeochemical cycles
Theoretical encounter kernel predictions demonstrate the influence of physics on microbial transport and encounter
The flow of carbon from microbial prey to viruses and grazers is controlled by additional phenomena that determine whether each encounter leads to successful capture (Equations 1 to 3)
Summary
Marine ecosystems include diverse microbial communities whose interactions mediate and drive biogeochemical cycles. Within these systems, photosynthetic primary producers, and heterotrophic bacteria are infected by viruses, and preyed upon by microzooplankton grazers (Dussart, 1965; Landry and Hassett, 1982; Bergh et al, 1989; Fuhrman and Noble, 1995; Sunagawa et al, 2015). Marine ecosystem models are increasingly resolving the diversity of metabolisms and traits that influence ecosystem function (Bruggeman and Kooijman, 2007; Follows et al, 2007; Stock et al, 2014; Weitz, 2015; Coles et al, 2017), but questions remain about how to empirically parameterize key interactions. Understanding viral and grazer impacts on microbial ecosystems requires a common framework connecting key traits that underly their mortality-inducing behaviors
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