Northern Australia is favoured for its substantial mineral reserves, with mining being a key economic activity within the landscape. Mines often lie in environments characterised by sharp mineralogical divides coupled with top of catchment temporary waters, yet little tailored guidance exists for how to effectively assess environmental quality in these ecosystems. Macroinvertebrate community assessments are a useful inclusion for compliance monitoring programs of temporary waters downstream of these mineralised zones. These highly ephemeral environments favour ecologies adapted to wide seasonal and annual variability in water availability and quality. The wet-dry season transition period is an important time to sample macroinvertebrate communities, coinciding with a period of high species diversity and abundance, but also high risks of contaminant impacts in the downstream environment.
One of the challenges in monitoring the health of mineralised temporary waters lies in disentangling mineralised influences upstream from natural disturbance events (e.g. wet season scouring flows). By their very nature, temporary waters typify diverse and changeable environments and unpredictable wetting-drying cycles. Natural changes in ecosystems associated with high seasonal and annual variability in climate and flow can confound the interpretation of monitoring results. Mineralised drainage emerging from upstream sites often exhibits elevated sulphate (SO42-) which can impart a stressor-response relationship on local macroinvertebrate community metrics and persist long after mining activities cease.
This presentation will use case study examples from four mineralised waterways in Northern Australia to explore macroinvertebrate community data along gradients of sulphate-rich mineralised drainage. Threshold analyses of macroinvertebrate indices will be explored to gauge the magnitude of mineralised influence during the changeable post-wet season drying out phase. Establishing methods to detect relationships between macroinvertebrate indices and sulphate-rich drainage in temporary waters is necessary to provide effective information for management of the downstream environment.