Mechanisms of coexistence between photosynthetic marine microbes and their viral and micrograzer predators

Photosynthetic marine microbes, both bacterial and eukaryotic, play a crucial role in ocean biogeochemistry and ecology through primary productivity. These microbes are preyed upon by heterotrophic nanoflagellates, zooplankton, and viruses, which coexist despite their competition for the same microbial prey. Here, we develop population dynamics models to investigate mechanisms facilitating the coexistence of a virus and a grazer preying upon a photosynthetic algae, either bacterial or eukaryotic: (i) the inclusion of an infected class of the algae, potentially subject to intraguild predation, where grazers feed on virally infected microbes; (ii) heterogeneity in susceptibility to infection, where microbes vary in their resistance to the virus either intracellularly or extracellularly; and (iii) the inclusion of quadratic mortality terms for the predators. Our results show that each of these mechanisms can facilitate virus and zooplankton coexistence within a specific range of the  virulence spectrum of the virus, shifting toward more virulent strategies for larger microbes. Additionally, we observe strong sensitivity of the models, including shifts in infected cell percentages and the balance between virally and zooplankton-induced mortality. Finally, we identify parameter combinations in models that yield realistic ecological properties across various simplified marine environments such as oligotrophic, mesotrophic, and upwelling regions. In doing so, the study represents an enabling step toward integration of models of lytic viruses in large ecosystem models.

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Primary Presenter: Paul Fremont, University of Maryland (pfremont@umd.edu)

Authors:

Stephen Beckett, University of Maryland  (beckett@umd.edu)

David Demory, Oceanography Observatory of Banyuls-sur-Mer  (david.demory@obs-banyuls.fr)

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

Joshua Weitz, University of Maryland  (jsweitz@umd.edu)