Effects of bushfire on macroinvertebrate communities in south-east Australian streams affected by a megadrought

Abstract

Bushfires occur in most environments in Australia and yet there are few studies about fire effects on aquatic ecosystems. To study the effects of fire on aquatic macroinvertebrates we sampled three streams in burnt catchments (i.e. burnt) and three streams in unburnt catchments (i.e. control), nine months after severe bushfires in northern Victoria. The sampling period coincided with a severe and prolonged period of drought – during the 8th year of a series of thirteen consecutive years of below average rainfall. There was a significant effect of bushfire on macroinvertebrate richness, composition and function. At the burnt sites, there was lower taxon richness but a 4-fold increase in abundance, which was mainly to the result of increases in taxa such as Chironomidae, Simuliidae, Dinotoperla sp. and Taschorema sp. A higher percentage of gathering collectors was found at the burnt sites, whereas scrapers and shredders were co-dominant in the control streams. The responses of the macroinvertebrates may have been impaired by post-fire persistence of low flows associated with the continuing drought, in comparison with the rapid recovery of the catchment overstorey vegetation (Eucalyptus spp.). The consequences of the megadrought combined with catchment bushfires, have no doubt reduced the resilience of the macroinvertebrate communities.