Unnamed creek, near Little Swamp
2010 Aquatic Ecosystem Condition Report
- Dry in autumn and slow-flowing stream present in spring.
- Sparse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of moderate nutrient enrichment.
- Riparian vegetation consisted of introduced grasses and rushes.
About the location
Unnamed Creek near Little Swamp is a small stream in Eyre Peninsula that rises north of Coomunga and drains in a south-easterly direction into the northern end of Little Swamp. The major land uses are sheep and cattle grazing and cropping.
The monitoring site was located off Flinders Highway, about eight kilometres north-west of Port Lincoln.
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, fine sediment deposition and poor riparian habitat.
A sparse community of about 25 species of macroinvertebrates was collected from the slow-flowing creek, five metres wide and 33 centimetres deep, in spring 2010; the site was dry in autumn. The community was dominated by a few species that are tolerant of poor water quality and high salinity, such as amphipods (Austrochiltonia australis) and notonectid waterbugs (Anisops). It also included low numbers of mites, springtails, beetles, mosquitoes, biting midges, soldierflies, chironomids, muscid fly larvae, waterbugs, odonates and leptocerid caddisflies. No sensitive or rare species were found.
The water was saline (salinity of 4,925 mg/L), well oxygenated (124% saturation), slightly turbid and coloured, with moderate to high concentrations of nutrients such as nitrogen (1.25 mg/L) and phosphorus (0.06 mg/L).
The sediments were dominated by clay, detritus and silt; samples taken from below the surface were occasionally black and anaerobic, an indication that too much organic matter had entered the creek in the past. A deposit of silt, 1–5 centimetres thick, covered the creekbed in places.
A moderate amount of phytoplankton occurred in the creek but filamentous algae was not recorded from either the dry channel in autumn or the wet channel in spring. Aquatic plants covered more than 10% of the site and included submerged (Chara) and emergent species (Juncus and Rumex) that were growing in the water and on the water’s edge.
The narrow riparian zone consisted of introduced grasses and rushes with a few gum trees and acacias. The surrounding vegetation at the site was cereal cropping land and grazed grassland.
Special environmental features
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.|