Salt Creek, near Sheoak Hill Conservation Reserve
2010 Aquatic Ecosystem Condition Report
- Permanently wet saline stream with flowing and non-flowing habitats present in autumn and spring.
- Sparse macroinvertebrate community of salt tolerant species and one rare caddisfly.
- Obvious signs of gross nutrient enrichment.
- Riparian vegetation limited to salt tolerant shrubs and groundcover species.
About the location
Salt Creek has the largest catchment area of any stream in Eyre Peninsula. It rises about 20 kilometres west of Mangalo and flows in an easterly direction before eventually draining onto the Uteralitera Plain to the north of Franklin Harbour. The major land use near the sampled site was native mallee vegetation but sheep grazing and cropping dominate land uses further upstream in the catchment.
The monitoring site was located at the ford on White Gate Road, about 30 kilometres north of Cowell.
The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure and moderate changes to the way the ecosystem functions. There was considerable evidence of human disturbance, including high salinity, nutrient enrichment, silt deposition and widespread vegetation clearance in the catchment.
A sparse community of about 10 species of macroinvertebrates was collected from the flowing stream, 13 metres wide and up to 45 centimetres deep, in autumn and spring 2010. The community consisted of only salt tolerant species and was dominated by large numbers of small snails (including Coxiella), beetles (Necterosoma penicillatus), and chironomids (Tanytarsus barbitarsis). It also included amphipods (Austrochiltonia), several other beetles (Laccobius and Berosus), biting midges, marchflies, soldierflies, and a leptocerid caddisfly (Symphitoneuria wheeleri). The latter species was the only rare species collected from the site. No flow-dependent species were recorded, despite the presence of suitable habitat in both seasons sampled. The only fish collected was a common native species called the Small-mouthed Hardyhead.
The water was very saline (salinity of 43,936 mg/L in autumn and 38,220 mg/L in spring), well oxygenated (110–121% saturation) and clear, with moderate to high concentrations of nutrients such as nitrogen (1.08–1.79 mg/L) and phosphorus (0.04–0.05 mg/L).
The sediments were dominated by bedrock, cobbles, pebbles and silt in the flowing sections and detritus, algae and silt in the non-flowing edge habitats. Samples taken from below the surface were black and sulfidic in spring, indicating that too much organic matter had entered the creek in the past. A deposit of 1–5 centimetres of silt covered the creekbed in spring.
Filamentous algae (Cladophora) covered more than 35% of the channel in spring and one submerged aquatic plant, the Sea Tassel (Ruppia), covered about 10% of the site in both seasons sampled.
The riparian zone consisted of salt tolerant scrubland and included acacias and samphire. The surrounding vegetation also consisted of salt tolerant scrub and included melaleucas, mallee gums, saltbush, grasses and samphire.
Special environmental features
Salt Creek provides habitat for one common native fish called the Small-mouthed Hardyhead and one rarely collected salt tolerant caddisfly (Symphitoneuria wheeleri). The creek was also one of only six streams sampled that had significant areas of flowing riffle habitats present in 2010.
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.|