Oral Presentation Australian Society for Limnology Congress 2013

Variability in ephemeral systems affects assessments of macro-invertebrate communities. (#31)

Claire Sellens 1
  1. CQ University, Rockhampton, QLD, Australia

The foot print from mining and grazing is extensive across Central Queensland. However, assessment of whether these land-uses are impacting on macroinvertebrates, as indicators of river health, is not straight forward. Minimally impacted reference sites are scarce in the region, and most streams and many rivers are ephemeral and intra-seasonal and inter-annual differences in community composition are strong.

The aim of this study was to define the changes in taxa composition in reference sites to understand how this affects the variability in commonly used indicators for river health. Macroinvertebrate data collected across the Fitzroy Basin over a 19 year period was examined to establish the range in PET, SIGNAL, and taxa richness scores at reference sites with different rainfall or flow conditions. The commonly assessed habitat, landscape, and meteorological data were also assessed to determine which variables most strongly aligned with changes or differences in taxa composition.

Analysis of the data set confirms that minimally impacted reference sites are scarce in the region, and that tolerant taxa are characteristic of all sites. Taxa richness is highly variable across sites; however PET scores are typically low with few Plecoptera and mostly tolerant Ephemeroptera and Trichoptera families. SIGNAL scores are less variable but typically indicate human impact even if absent.

Assessments of river health in the Central Queensland region need to be made with consideration to the natural variability of macroinvertebrate communities and the very strong effect of inter-annual differences based on characteristics of the wet season.