Experimental and modeling studies of a four-trophic level predator-prey system

Experimental studies of a microbial food chain involving organic carbon substrates, Enterobacter aerogenes, and ciliate protozoans Paramecium primaurelia and Didinium nasutum were conducted in stirred, aerated batch cultures. Quantitative measurements were made of organic carbon levels and of cell numbers, mean cell volumes, and total biovolumes for all three microbial populations. A mathematical model based on Monod kinetics was developed to describe this four-trophic level predator-prey system. The model was formulated in terms of biovolume, which is the product of cell numbers and mean cell size, and includes terms for bio-volume decay. Batch culture data were used to derive parameter values, and model simulations were compared to experimental results. Despite the significance of Paramecium-Didinium studies in ecological literature, the entire food chain has not been previously studied or modeled.