Macroinvertebrate recolonization after re-wetting of a tropical seasonally-flowing stream (Magela Creek, Northern Territory, Australia)

Abstract

Magela Creek, a tropical stream in northern Australia, dries out for most of its length for approximately 6 months of the year. At the end of the dry season, the macroinvertebrate fauna of the perennial upper reaches and lowland billabongs were sampled, as well as resting stages of the fauna in the dry sandy streambed. With the resumption of wet-season flow, drift and benthos were sampled from three sites along the sand tract of the creek over the ensuing four weeks. Recolonization commenced rapidly after first flow. Most taxa were derived from the perennial upper reaches through drift, but contributions from an adjacent billabong and resting stages in the substratum were important in the early stages of species establishment at the most downstream site. The dry sandy sediments were also a significant refuge for microcrustaceans. On the basis of this work and a review of other research, it is concluded that the significance of dry-season refuges to recolonization of temporary streams when flow resumes is governed by the nature of the substratum, the severity of the dry season and the proximity of the stream to permanent waters.