Influence of Irradiance and Temperature on the Virus MpoV-45T Infecting the Arctic Picophytoplankter Micromonas polaris.

Gonçalo Piedade,Douwe Maat,Corina Brussaard,Elena Montenegro-Borbolla,Ella Wesdorp

doi:10.3390/v10120676

Abstract

Arctic marine ecosystems are currently undergoing rapid changes in temperature and light availability. Picophytoplankton, such as Micromonas polaris, are predicted to benefit from such changes. However, little is known about how these environmental changes affect the viruses that exert a strong mortality pressure on these small but omnipresent algae. Here we report on one-step infection experiments, combined with measurements of host physiology and viability, with 2 strains of M. polaris and the virus MpoV-45T under 3 light intensities (5, 60 and 160 μmol quanta m−2 s−1), 2 light period regimes (16:8 and 24:0 h light:dark cycle) and 2 temperatures (3 and 7 °C). Our results show that low light intensity (16:8 h light:dark) delayed the decline in photosynthetic efficiency and cell lysis, while decreasing burst size by 46%. In contrast, continuous light (24:0 h light:dark) shortened the latent period by 5 h for all light intensities, and even increased the maximum virus production rate and burst size under low light (by 157 and 69%, respectively). Higher temperature (7 °C vs 3 °C) led to earlier cell lysis and increased burst size (by 19%), except for the low light conditions. These findings demonstrate the ecological importance of light in combination with temperature as a controlling factor for Arctic phytoplankton host and virus dynamics seasonally, even more so in the light of global warming.

Highlights

Viruses are important mortality agents of phytoplankton, exerting a substantial top-down control on their host populations [1,2,3,4,5,6,7]
Our results show that irradiance and temperature strongly affect interactions between M. polaris and MpoV-45T
Reduced light intensity (LL) prolonged the latent period, lowered maximum viral production rates, and subsequently diminished the burst size under all the temperature and light period conditions tested for both host strains

Summary

Introduction

Viruses are important mortality agents of phytoplankton, exerting a substantial top-down control on their host populations [1,2,3,4,5,6,7] They act as key modulators of the microbial food web and as such, biogeochemical cycling and trophic efficiency [8,9]. Viruses 2018, 10, 676 and to what extent the predicted global climate change-induced alterations in physicochemical variables impact the ecological role of marine viruses Polar regions, such as the Arctic, are subjected to strong seasonal variations in light, temperature, and salinity. Reduced ice cover, earlier and strengthened salinity-induced vertical stratification of the upper water column, increased sediment input from melting glaciers and increased coastal erosion and river flow will affect light availability in Arctic coastal waters [13,17]

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