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 (Basel) 2021-02, Vol.9 (2), p.460
Main Authors: Evans, Claire, Brandsma, Joost, Meredith, Michael P, Thomas, David N, Venables, Hugh J, Pond, David W, Brussaard, Corina P D
Format: Article
Language:English
Subjects:
Antarctica
Bacteria
Bacterioplankton
Carbon
Coastal processes
Coastal waters
Food chains
Food webs
Grazing
heterotrophic nanoflagellates
Infections
microbial loop
Microorganisms
Plankton
Pore size
prokaryotes
Regeneration
Remineralization
Respiration
Seawater
Secondary production
Trophic levels
Viral infections
viral shunt
Viruses
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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 day on average in December and January to 2.4 µg C L day in February. Conversely, carbon flow through the viral shunt increased substantially over the study from on average 0.9 µg C L day in December to 7.6 µg C L day 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.
ISSN:2076-2607
2076-2607
DOI:10.3390/microorganisms9020460