AME 52:45-55 (2008)  -  DOI: https://doi.org/10.3354/ame01200

Predation pressure on bacteria increases along aquatic productivity gradients

Johanna Thelaus1,2,*, Pia Haecky3,5, Mats Forsman2, Agneta Andersson1,4

1Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden
2CBRN Defence and Security, Swedish Defence Research Agency, 901 82 Umeå, Sweden
3Botanical Institute, University of Copenhagen, Oster Farimagsgade 2D, 1353 Copenhagen K, Denmark
4Umeå Marine Sciences Centre, 910 20 Hörnefors, Sweden
5Present address: Bioras, Munkegårdsvej 6B, 3490 Kvistgård, Denmark

ABSTRACT: To elucidate how predation pressure on bacteria is affected by increasing productivity in aquatic systems, we ran model simulations of a microbial food web. In addition, we conducted a meta-analysis of data from studies in seas and lakes. The model was run as a flow-through system simulating conditions ranging from oligotrophic to hypertrophic. The organisms included in the model were heterotrophic bacteria, phytoplankton, 3 size classes of protozoa and metazooplankton. Predation pressure was defined as flagellate and ciliate grazing per bacterial biomass. The food-web model simulations showed increasing predation pressure on bacteria with increasing productivity (estimated chlorophyll a concentration 0.2 to 112 µg l–1). This was explained by an increase in bacterial production and the ratio of protozoan to bacterial biomass with increasing productivity. The results of the model simulation were supported by the meta-analysis, which showed increasing protozoan predation pressure on bacteria with increasing productivity in aquatic systems (chlorophyll a concentration 0.1 to 250 µg l–1). The ratio of protozoan to bacterial biomass also increased with productivity in the meta-analysis of field data. Our results suggest that protozoa control the bacterial community by predation in high-productivity environments.


KEY WORDS: Bacteria · Protozoa · Predation · Microbial food web · Productivity · Regulation · Model · Omnivory


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Cite this article as: Thelaus J, Haecky P, Forsman M, Andersson A (2008) Predation pressure on bacteria increases along aquatic productivity gradients. Aquat Microb Ecol 52:45-55. https://doi.org/10.3354/ame01200

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