Unnamed creek, near Charlton Springs
2010 Aquatic Ecosystem Condition Report
- Permanently wet creek consisting of slow-flowing habitats in autumn and a non-flowing channel in spring.
- Moderately diverse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of moderate to gross nutrient enrichment.
- Riparian vegetation consisted of introduced grasses and native trees.
- Moderately eroded banks and large silt deposit in the channel.
About the location
Unnamed Creek near Charlton Springs is a small stream in Eyre Peninsula that rises east of Wanilla and drains in a westerly direction before discharging into the Tod River near Kullenboo. The major land uses are grazing and cropping, and minor areas of native vegetation.
The monitoring site was located off Charlton Gully Road, about seven kilometres south-west of Whites Flat.
The creek was given a Fair rating because the site sampled showed moderate changes in ecosystem structure and some changes to the way the ecosystem functions. There was evidence of human disturbance, including nutrient enrichment, poor riparian habitat, bank erosion and fine sediment deposition, although the stream still provided an important refuge for many species of macroinvertebrates and frogs.
A moderately diverse community of about 32 species of macroinvertebrates was collected from the creek, 8–11 metres wide and 25 centimetres deep, in autumn and spring 2010. The creek consisted of a slow-flowing channel in autumn but had ceased to flow when the spring sampling period was carried out. The macroinvertebrate community was dominated by species tolerant to poor water quality such as chironomids (including Chironomus) and planorbid snails (Glyptophysa). It also included smaller numbers of lymnaid snails, worms, mites, amphipods, beetles, mosquitoes, soldierflies, marshflies, waterbugs, odonates and leptocerid caddisflies. No sensitive or rare species were found. The site also lacked any flow-dependent species, despite the presence of small areas of fast-flowing riffle habitat in autumn.
The water was moderately fresh to saline (salinity of 5,000 mg/L in autumn to 2,507 mg/L in spring), well oxygenated (70–125% saturation) and clear, with moderate to high concentrations of nutrients such as nitrogen (1.03–1.15 mg/L) and phosphorus (0.01–0.04 mg/L).
The sediments were dominated by detritus, clay, silt and algae; samples taken from below the surface were aerobic in autumn but sulfidic and lacking in oxygen in spring. A deposit of 5–10 centimetres of silt covered the creekbed in autumn and more than 10 metres of the banks showed signs of erosion, due to stormwater runoff from the nearby road.
A small amount of filamentous algae (Cladophora) was present in spring, when it covered less than 10% of the site, but it was not detected in autumn. Over 35% of the site was covered by emergent aquatic plants (Callitriche, Cotula, Eleocharis, Polygonum, Juncus and Rumex) which were growing in the channel and on the banks.
The riparian zone consisted of introduced grasses and sedges (Isolepis and Eleocharis), with some patches of gums trees also present. The surrounding vegetation was mostly grazed paddocks with a few patches of native vegetation.
Special environmental features
This small unnamed creek supports a rich assemblage of commonly occurring macroinvertebrate species from the region. It also provided habitat for up to five different frog species that were heard calling near the site during the 2010 surveys.
Pressures and management responses
|Livestock have direct access at the site and upstream in the catchment, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||
The Eyre Peninsula NRM Board promotes managing land to improve water quality. This includes incentives for:
|Limited natural riparian vegetation at the site and upstream in the catchment, providing minimal buffer protection from catchment landuses (reducing habitat quality).|
|Saline groundwater inflow (reducing ecological integrity).||The Eyre Peninsula NRM Board promotes the revegetation of recharge areas known to contribute to dryland salinity and encourages the adoption of perennial pastures as an alternative to annual cropping in these areas.|