Computer simulations of some complex microbial food chains

• Published in: Water research (Oxford) 1974-01, Vol.8 (10), p.769-780
• Main Author: Curds, C.R.
• Format: Article
• Language: English
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/0043-1354(74)90022-0

Mathematical models of a variety of microbial food chains and webs have been derived which consider the fates of soluble substrates, heterotrophic bacteria and ciliated protozoa. Computer simulation techniques have been used to study the dynamic behaviour of these organisms in a single-stage continuous-culture reactor. The food chains simulated include series dealing with the effect of predatory cilates upon competing bacteria; the concurrent utilization of food supplies: and the concurrent utilization of food supplies by competing organisms. Simulations have suggested that the predatory activities of ciliated protozoa can promote the survival of two competing bacteria whereas one of the bacteria would usually be washed out of the system in the absence of the predator. These models were depending upon the values of the kinetic constants of the organisms concerned, either dynamically stable or exhibited simple limit-cycle behaviour. Concurrent utilization of food supplies according to the experimental data of Stumm-Zollinger (1966) has been modelled and simulations predict steady-state solutions when predators are absent. In addition, concurrent utilization of food supplies by competing organisms in the presence and absence of predatory ciliates has been modelled and simulated. In some cases the variations in the constituent populations observed in these complex food webs were found to be of a non-repetitive nature within the simulated time scale of 300 h, whereas limit-cycle behaviour is usually observed in simple predator-prey food chains.