The Response of Heterotrophic Prokaryote and Viral Communities to Labile Organic Carbon Inputs Is Controlled by the Predator Food Chain Structure

Factors controlling the community composition of marine heterotrophic prokaryotes include organic-C, mineral nutrients, predation, and viral lysis. Two mesocosm experiments, performed at an Arctic location and bottom-up manipulated with organic-C, had very different results in community composition...

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Bibliographic Details
Published in:Viruses
Main Authors: Ruth-Anne Sandaa, Bernadette Pree, Aud Larsen, Selina Våge, Birte Töpper, Joachim P. Töpper, Runar Thyrhaug, Tron Frede Thingstad
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2017
Subjects:
marine viral diversity
viral–host interaction
high latitude microbes
minimum food web model
copepods
ciliates
nutrient limitation
trophic cascade
Microbiology
QR1-502
Arctic
Copepods
Online Access:https://doi.org/10.3390/v9090238
https://doaj.org/article/8e00caa562b547c2a58a7d4be07b930c
Description
Summary:Factors controlling the community composition of marine heterotrophic prokaryotes include organic-C, mineral nutrients, predation, and viral lysis. Two mesocosm experiments, performed at an Arctic location and bottom-up manipulated with organic-C, had very different results in community composition for both prokaryotes and viruses. Previously, we showed how a simple mathematical model could reproduce food web level dynamics observed in these mesocosms, demonstrating strong top-down control through the predator chain from copepods via ciliates and heterotrophic nanoflagellates. Here, we use a steady-state analysis to connect ciliate biomass to bacterial carbon demand. This gives a coupling of top-down and bottom-up factors whereby low initial densities of ciliates are associated with mineral nutrient-limited heterotrophic prokaryotes that do not respond to external supply of labile organic-C. In contrast, high initial densities of ciliates give carbon-limited growth and high responsiveness to organic-C. The differences observed in ciliate abundance, and in prokaryote abundance and community composition in the two experiments were in accordance with these predictions. Responsiveness in the viral community followed a pattern similar to that of prokaryotes. Our study provides a unique link between the structure of the predator chain in the microbial food web and viral abundance and diversity.

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