Reproducing the virus‐to‐copepod link in Arctic mesocosms using host fitness optimization

T Frede Thingstad,Selina Våge,Jorun Egge,Jens Christian Nejstgaard,Ruth‐Anne Sandaa,Gunnar Bratbak,Aud Larsen

doi:10.1002/lno.11549

Abstract

AbstractBy shunting material out of the predatory pathway toward detritus and dissolved material, viruses are believed to have an important impact on biogeochemical functions of the pelagic microbial food web. To include viruses as a single plankton functional type (PFT) in dynamic food web models is, however, not trivial since they will then compete with predators for the same host/prey community as a shared limiting resource. As recently shown, one can solve this problem by introducing adaptation in the defensive and competitive traits of the host (prey) community. We here show how this can reproduce central aspects of viral dynamics as observed in a set of Arctic mesocosm experiments. In these experiments, contrasting microbial trophodynamics have previously been linked to the trophic cascades generated by seasonal vertical migration of large Arctic copepods. This approach thus produces a quantitative theory for the mechanisms regulating virus‐to‐prokaryote and lysis‐to‐predation ratios, and integrates this with a central role of predator top‐down control in pelagic microbial food webs.

Highlights

It is in principle possible to combine this minimum model with a dynamic description of viruses that resolves the prokaryote community to species or even to strain level (Thingstad et al 2014; Våge et al 2016), but gives a substantial increase in the number of plankton functional types (PFTs) and model complexity, reducing the conceptual transparency
With a model able to capture central aspects of microbial food web trophodynamics, we wanted here to explore whether the observed variations in viral abundances (Sandaa et al 2017) could be reproduced using the technique with an adaptive bacterial community
To prevent predation from reducing bacterial abundance too much, and thereby creating unrealistically high virus-tobacteria ratio (VBR) values, a lower prey limit (Blim, Table 1) for predation on bacteria is added to the minimum model

Summary

Introduction

With a model able to capture central aspects of microbial food web trophodynamics, we wanted here to explore whether the observed variations in viral abundances (Sandaa et al 2017) could be reproduced using the technique with an adaptive bacterial community. To prevent predation from reducing bacterial abundance too much, and thereby creating unrealistically high virus-tobacteria ratio (VBR) values, a lower prey limit (Blim, Table 1) for predation on bacteria is added to the minimum model.

Results

Conclusion