Shift from Carbon Flow through the Microbial Loop to the Viral Shunt in Coastal Antarctic Waters during Austral Summer

The relative flow of carbon through the viral shunt and the microbial loop is a pivotal factor controlling the contribution of secondary production to the food web and to rates of nutrient remineralization and respiration. The current study examines the significance of these processes in the coastal...

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Bibliographic Details
Published in:Microorganisms
Main Authors: Claire Evans, Joost Brandsma, Michael P. Meredith, David N. Thomas, Hugh J. Venables, David W. Pond, Corina P. D. Brussaard
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2021
Subjects:
prokaryotes
Antarctica
viruses
heterotrophic nanoflagellates
microbial loop
viral shunt
Biology (General)
QH301-705.5
Antarctic
Austral
The Antarctic
Antarc*
Online Access:https://doi.org/10.3390/microorganisms9020460
https://doaj.org/article/7e0d7cd9bfb24dd99db216e80c5aa81c
Description
Summary:The relative flow of carbon through the viral shunt and the microbial loop is a pivotal factor controlling the contribution of secondary production to the food web and to rates of nutrient remineralization and respiration. The current study examines the significance of these processes in the coastal waters of the Antarctic during the productive austral summer months. Throughout the study a general trend towards lower bacterioplankton and heterotrophic nanoflagellate (HNF) abundances was observed, whereas virioplankton concentration increased. A corresponding decline of HNF grazing rates and shift towards viral production, indicative of viral infection, was measured. Carbon flow mediated by HNF grazing decreased by more than half from 5.7 µg C L −1 day −1 on average in December and January to 2.4 µg C L −1 day −1 in February. Conversely, carbon flow through the viral shunt increased substantially over the study from on average 0.9 µg C L −1 day −1 in December to 7.6 µg C L −1 day −1 in February. This study shows that functioning of the coastal Antarctic microbial community varied considerably over the productive summer months. In early summer, the system favors transfer of matter and energy to higher trophic levels via the microbial loop, however towards the end of summer carbon flow is redirected towards the viral shunt, causing a switch towards more recycling and therefore increased respiration and regeneration.

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