Viral lysis modifies seasonal phytoplankton dynamics and carbon flow in the Southern Ocean

Abstract Phytoplankton form the base of marine food webs and are a primary means for carbon export in the Southern Ocean, a key area for global pCO 2 drawdown. Viral lysis and grazing have very different effects on microbial community dynamics and carbon export, yet, very little is known about the r...

Full description

Bibliographic Details
Published in:The ISME Journal
Main Authors: Biggs, Tristan E. G., Huisman, Jef, Brussaard, Corina P. D.
Other Authors: Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Format: Article in Journal/Newspaper
Language:English
Published: Springer Science and Business Media LLC 2021
Subjects:
Online Access:http://dx.doi.org/10.1038/s41396-021-01033-6
https://www.nature.com/articles/s41396-021-01033-6.pdf
https://www.nature.com/articles/s41396-021-01033-6
Description
Summary:Abstract Phytoplankton form the base of marine food webs and are a primary means for carbon export in the Southern Ocean, a key area for global pCO 2 drawdown. Viral lysis and grazing have very different effects on microbial community dynamics and carbon export, yet, very little is known about the relative magnitude and ecological impact of viral lysis on natural phytoplankton communities, especially in Antarctic waters. Here, we report on the temporal dynamics and relative importance of viral lysis rates, in comparison to grazing, for Antarctic nano- and pico-sized phytoplankton of varied taxonomy and size over a full productive season. Our results show that viral lysis was a major loss factor throughout the season, responsible for roughly half (58%) of seasonal phytoplankton carbon losses. Viral lysis appeared critically important for explaining temporal dynamics and for obtaining a complete seasonal mass balance of Antarctic phytoplankton. Group-specific responses indicated a negative correlation between grazing and viral losses in Phaeocystis and picoeukaryotes, while for other phytoplankton groups losses were more evenly spread throughout the season. Cryptophyte mortality was dominated by viral lysis, whereas small diatoms were mostly grazed. Larger diatoms dominated algal carbon flow and a single ‘lysis event’ directed >100% of daily carbon production away from higher trophic levels. This study highlights the need to consider viral lysis of key Antarctic phytoplankton for a better understanding of microbial community interactions and more accurate predictions of organic matter flux in this climate-sensitive region.