Abstract
Substrate supply and grazing are the factors with the greatest potential for short-term control of planktonic bacterial density and productivity. A model was developed based on Monod kinetics, where growth rates are limited by food supply in a saturation type equation. In the model, substrate, bacteria, heterotrophic flagellates and zooplankton are state variables linked by trophic transfer and expressed as carbon. The steady state assumption allows calculation of equations indicating the following: (l) bacterial density is determined primarily by the ratio of substrate input to grazing rate; (2) bacterial production is balanced by a combination of losses due to maintenance, death and grazing, and occurs at a rate determined by the rate of substrate input and the growth yield; (3) ambient substrate concentration is directly related to grazing rate.
Sensitivity analysis of the model on a computer demonstrates some differences between grazer-controlled and substrate-controlled bacterial systems, and predictions of the model are listed for possible validation in natural systems. The model is potentially useful in evaluating the ‘link vs. sink’ question, as it provides a framework for investigating energy flow through the microbial food web as a function of controlling factors.
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Wright, R.T. A model for short-term control of the bacterioplankton by substrate and grazing. Hydrobiologia 159, 111–117 (1988). https://doi.org/10.1007/BF00007372
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DOI: https://doi.org/10.1007/BF00007372