A dynamic model of fungal spora in a freshwater stream

A continuous systems model has been used to clarify the dynamics of populations of fungal spores in a body of water moving down an idealized stream. A simple graphical method has been developed for analysing spore inputs and outputs, applicable to relatively stable sections of streams lacking perturbing factors. This analytical method has been tested using data obtained from an Australian upland stream, and its practicability demonstrated. Three classes of behaviour were distinguished: species whose spores appeared to be added at a constant arithmetical rate over distance; species whose spores were added at a constant geometrical rate over distance as if by an autocatalytic process; and species whose spores were added at variable rates over distance. For species in the first category, where input and output rates could be reliably estimated, input of spores ranged from 8 to 200 l −1 km −1, but their persistence, expressed as half-lives, was almost identical at 0·7–0·8 km.