Malcolm Creek tributary, near Kersbrook
2008 Aquatic Ecosystem Condition Report
- Affected by nutrient enrichment and fine sediment.
- Diverse macroinvertebrate community dominated by species tolerant of pollution, with some sensitive species still present.
- Limited riparian zone invaded by weeds.
- Streambanks heavily eroded by livestock.
About the location
This small stream rises in the Watts Gully Native Forest Reserve near Kersbrook. It flows west through cattle and sheep grazing country before crossing the Little Para Road and joining Malcolm Creek, which ultimately flows into the South Para Reservoir at Red Gum Flat.
The monitoring site was located northeast of Kersbrook off South Para Road, 400 metres north of the junction with Watts Gully Road.
The river was given a Fair rating at this site because the ecosystem showed moderate changes to animal and plant life, and some changes to the way the ecosystem functions. There was considerable evidence of human impact, including nutrient enrichment and the presence of large amounts of fine sediment.
At the time of monitoring in November 2008, the stream was one to two metres wide and consisted of shallow pools connected by very small areas of flowing riffles.
The pools supported a diverse community of 49 macroinvertebrate species. The most numerous were worms, small crustaceans called scuds (Austrochiltonia australis) and several types of chironomids. More than 68% of the community were species that feed on organic material and are tolerant to high nutrient levels and poor water quality. Sensitive, rare species were restricted to low numbers of a mayfly and stonefly, and a single fly larva from the family Dixidae.
The water was moderately fresh (salinity of 1,123 mg/L) and well oxygenated (70% saturated. It was clear of suspended sediment but was strongly coloured by naturally occurring tannins, and had moderate to high concentrations of nutrients such as nitrogen (0.7 mg/L) and phosphorus (0.06 mg/L).
A large amount of small algae called phytoplankton was found in the water, as well as two types of green filamentous algae (Cladophora and Spirogyra). Most of the stream contained the submerged plant stonewort (Chara); a range of emergent plants grew on the edges, including Water Ribbons (Triglochin), rush (Juncus), starwort (Callitriche), spikerush (Eleocharis), sedge(Isolepis), dock (Ruxex) and loosestrife (Lythrum).
Sediments found on the bottom of the channel included organic debris, or detritus, made up of decomposed plants and animals–an indication the stream occasionally receives high nutrient loads. Fine silt, clay and sand were also found on the streambed, and the banks were heavily eroded by cattle.
A line of River Red Gums grew along the edge of the creek over blackberries and introduced grasses and weeds, with patches of willows located both upstream and downstream from the sampled site. Beyond the riparian zone, the surrounding vegetation was variable, with patches of River Red Gum woodland interspersed with introduced pastures.
Special environmental features
The creek provides habitat for at least three rare and sensitive types of macroinvertebrates, including the mayfly (Atalophlebia australis), stonefly (Austrocerca tasmanica) and larva from the family Dixidae.
Pressures and management responses
|Large decrease in natural water flows (reducing ecological integrity).||Through water allocation planning the Adelaide and Mount Lofty Ranges NRM Board seeks to manage a sustainable water supply for the region so that there is enough water available for everyone (including the environment) even in drought conditions.|
|Livestock have direct access at the site and upstream, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes incentives for waterway and wetland fencing to exclude or limit stock from entering riparian zones.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes incentives for revegetation programs around waterways and wetlands and stock exclusion as well as educating landholders about the importance of riparian vegetation in managing soil erosion.|
This aquatic ecosystem condition report is based on monitoring data collected by the EPA and prepared in conjunction with the Adelaide and Mount Lofty Ranges NRM Board.