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Instream biota is the life that lives within the stream and typically comprises animals (fish and macroinvertebrates) and plants (algae and macrophytes).
Macroinvertebrates
Aquatic macroinvertebrates are very useful indicators in biological monitoring. They are visible to the naked eye and are commonly found in streams.
They are an important source of food for fish, and many are well known to anglers - such as yabbies, mudeyes, stoneflies and mayflies. They are widespread, easy to collect, relatively immobile and reflect the build-up of impacts of environmental change on the stream ecosystem.
AUSRIVAS
The Australian Rivers Assessment System (AUSRIVAS) is a standardised national predictive assessment scheme for evaluating river health. AUSRIVAS provides an integrated indicator of condition; incorporating water quality, habitat assessment and macroinvertebrate diversity measures that reflect the build-up of impacts of environmental change on the river ecosystem - such as the influence of surrounding land use or the effect of pollution.
AUSRIVAS consists of several mathematical models which use information from minimally impacted sites (reference) to predict the aquatic macroinvertebrate families which would be expected to be present in similar specific stream habitats under reference conditions, that is, if there were no environmental impacts.
By comparing the probabilities of predicted families and the number of families actually found, a ratio can be calculated for each site. This ratio is expressed as the observed number of families/expected number of families (the O/E score).
These O/E scores can then be compared to categories (or bands) representing different levels of biological condition This allows an assessment of the level of impact on the site. Combining this with general catchment assessment, allows the general health of the reach of the stream that was sampled to be characterised.
While AUSRIVAS does not provide the specific cause of the disturbance, it enables the condition of individual rivers and streams to be placed in a statewide or regional context, allowing identification of priority needs for further investigation and management action.
Contact: Leon Metzeling Freshwater Sciences, Environment Protection Authority 03 9628 5954 for more information.
email: leon.metzeling@epa.vic.gov.au
An adult mayfly
Photo: EPA
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Invertebrates which are sensitive to pollution, such as the immature forms of stoneflies, mayflies and caddisflies, are often found in upland streams.
Photo: Museum of Victoria
These invertebrates are typically found in foothill or lowland streams which are still in fairly good condition.
Photo: Museum of Victoria
Pollution commonly reduces biodiversity. At times only pollution tolerant forms such as worms and midge larvae survive in streams.
Photo: Museum of Victoria
Diatoms are typically single celled algae which either float in the water column or live attached to the stream bottom. The type of diatoms present in a stream are a good indicator of the stream’s nutrient status.
Photo: EPA |
