Interactive effects of viral lysis and warming in a coastal ocean identified from an idealized ecosystem model

Marine viruses have been identified as key players in biogeochemical cycles and in the termination of phytoplankton blooms; however, most biogeochemical models have yet to resolve viral dynamics. Here, we incorporate a viral component into a 1D ecosystem model to explore the influence of viruses on ecosystem dynamics under current and future climatic conditions in a coastal ocean. Virus-phytoplankton interactions and zooplankton grazing were mechanistically described through size-based contact rates. The model demonstrated that the presence of viruses increased nutrient retention in the upper water column. This corresponded to a reduction in phytoplankton biomass, production of dead organic matter and transfer of biomass to higher trophic levels. Viral presence played a key role in deeper water layers, near the thermocline. While warming alone reversed these trends, the combination of warming and viral presence enhanced the effect of viruses, indicative of synergistic interaction. Our results highlight the need of incorporating viral dynamics in the existing marine ecosystem models to better predict ecosystem responses to climate change.