Macroinvertebrate colonization of stones in two upland southern Australian streams

Abstract

Experiments on the colonization by macroinvertebrates of stones were performed in the Acheron and Toorongo Rivers, two upland rivers in south-eastern Australia. The three experiments were each about one month in duration. In the first experiment — Acheron I — and the third experiment — Toorongo — river stones were used. In the Acheron II experiment both river stones and quarry stones were used. The number of colonizing species with time in the Acheron I and Toorongo experiments fitted a logarithmic model with the colonization and elimination (extinction) rates both declining with time. The population densities of the total animals and of most of the common species fitted the power model (linear model on logarithmically transformed axes). In the Acheron II experiment the major difference between the colonization of river stones and quarry stones was the low numbers of scrapers on the quarry stones. The colonization of the stones in Acheron I and Toorongo by the various functional feeding groups is described. The colonization of stones in streams is a rapid process suggesting that the stream stone assemblage has a high resilience — an attribute of deterministic communities.