Biodiversity in headwater streams

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Amber Clarke, a Monash University and eWater PhD student, is investigating the diversity of macroinvertebrates in headwater streams in the predominantly Mountain Ash forests of the Wallaby Creek Designated Water Supply Catchment Area, of Victoria.

Image: Measuring flow in one of the study streams.

After reviewing the literature, she says such streams are actually a major component of river networks. Collectively they may constitute more than three-quarters of the total stream channel length in drainage basins.

Amber's investigation into the effect of flow permanence on diversity, conducted during the current decade-long drought, gives some idea of the consequences of drying disturbance in headwater streams.

Results indicate that during a dry summer period, in the two streams where surface flow dried out, the mean biodiversity and abundance of the macroinvertebrates fell, and the drying period produced different patterns in community composition.

“However, during the wet spring period, the macroinvertebrate communities in the three little streams showed very similar diversity, abundance and composition.

Image: Preserving macroinvertebrate samples to take back to the laboratory.

“Such findings,” says Amber, “provide some insight into the changes we can expect in macroinvertebrate stream communities as local and regional climates become drier due to climate change and increased water abstraction.”