Viral-Mediated Microbe Mortality Modulated by Ocean Acidification and Eutrophication: Consequences for the Carbon Fluxes Through the Microbial Food Web

• Published in: Frontiers in Microbiology
• Main Authors: Malits, Andrea, Boras, Julia A., Balagué, Vanessa, Calvo, Eva María, Gasol, Josep M., Marrasé, Cèlia, Pelejero, Carles, Pinhassi, Jarone, Sala, M. Montserrat, Vaqué, Dolors
• Other Authors: Ministerio de Economía y Competitividad (España), Generalitat de Catalunya, Ministerio de Educación (España), Agencia Estatal de Investigación (España)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media 2021
• Subjects: Ocean acidification; Eutrophication; Microbial food web; Viral shunt; Carbon fluxes
• Online Access: http://hdl.handle.net/10261/239040; https://doi.org/10.3389/fmicb.2021.635821; https://doi.org/10.13039/501100011033; https://doi.org/10.13039/501100002809; https://doi.org/10.13039/501100003329

19 pages, 4 figures, 4 tables, supplementary material https://doi.org/10.3389/fmicb.2021.635821.-- The original contributions presented in the study are included in the article/Supplementary Materials, further inquiries can be directed to the corresponding authors Anthropogenic carbon emissions are causing changes in seawater carbonate chemistry including a decline in the pH of the oceans. While its aftermath for calcifying microbes has been widely studied, the effect of ocean acidification (OA) on marine viruses and their microbial hosts is controversial, and even more in combination with another anthropogenic stressor, i.e., human-induced nutrient loads. In this study, two mesocosm acidification experiments with Mediterranean waters from different seasons revealed distinct effects of OA on viruses and viral-mediated prokaryotic mortality depending on the trophic state and the successional stage of the plankton community. In the winter bloom situation, low fluorescence viruses, the most abundant virus-like particle (VLP) subpopulation comprising mostly bacteriophages, were negatively affected by lowered pH with nutrient addition, while the bacterial host abundance was stimulated. High fluorescence viruses, containing cyanophages, were stimulated by OA regardless of the nutrient conditions, while cyanobacteria of the genus Synechococcus were negatively affected by OA. Moreover, the abundance of very high fluorescence viruses infecting small haptophytes tended to be lower under acidification while their putative hosts' abundance was enhanced, suggesting a direct and negative effect of OA on viral–host interactions. In the oligotrophic summer situation, we found a stimulating effect of OA on total viral abundance and the viral populations, suggesting a cascading effect of the elevated pCO2 stimulating autotrophic and heterotrophic production. In winter, viral lysis accounted for 30 ± 16% of the loss of bacterial standing stock per day (VMMBSS) under increased pCO2 compared to 53 ± 35% in the control treatments, ...