Population dyanamics and element recycling in an aquatic plant herbivore system

We construct a model of an aquatic plant-herbivore system which takes explicit account of the cycling of the element limiting plant growth. The work is motivated by experiments on the population dynamics of the waterflea Daphnia where the Daphnia population is regulated by the availability of algal food, but the algae are phosphorus limited. The model is used to investigate the possibility that the system may be stabilised by a mechanism in which the Daphnia constitute a temporary phosphorus “sink”. We conclude that this is unlikely if the system is closed to external input of the nutrients limiting plant growth.