Currency Creek, near Scott Conservation Park
2010 Aquatic Ecosystem Condition Report
- Permanently flowing, moderately fresh to slightly saline creek with large areas of riffle habitat present in spring.
- Moderately diverse macroinvertebrate community with some rare and sensitive species.
- Obvious signs of moderate nutrient enrichment.
- Riparian vegetation consists of River Red Gums and introduced grasses.
About the location
Currency Creek is a moderately large stream in the southern Mount Lofty Ranges that rises to the west of Mosquito Hill, flows east and eventually discharges into the Lower Murray to the north of Goolwa. The major land use is sheep grazing, with minor areas of rural residential living and native vegetation. The monitoring site was located at Stuarts Bridge on the Mount Compass to Goolwa Road, about three kilometres south of Scott Conservation Park.
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 and fine sediment deposition, although the stream still provided an important refuge for some sensitive macroinvertebrate species.
A moderately diverse community of about 33 species of macroinvertebrates was collected from the flowing creek, 2–4 metres wide and up to 60 cm deep, in autumn and spring 2010. Fast-flowing riffle habitat was present in both seasons but was only extensive enough to sample in spring. The community was dominated by large numbers of only a few species that are tolerant to poor water quality such as amphipods (Austrochiltonia australis) and marsh beetles (Family Scirtidae). It also included smaller numbers of introduced snails (Potamopyrgus antipodarum and Physa), freshwater limpets, worms, mites, isopods, freshwater shrimp, yabbies, beetles, mosquitoes, biting midges, blackflies, chironomids, mayflies, waterbugs, dragonflies, stoneflies and caddisflies.
A few rare and sensitive species were collected, including the leptophlebiid mayfly (Koorrnonga inconspicua) and two stoneflies (unidentified specimens from the Family Gripopterygidae and Austrocerca tasmanica from the Family Notonemouridae). Several species normally associated with flowing habitats were also collected, mostly from the riffle habitats in spring, including a dytiscid beetle (Platynectes decempunctatus), blackfly larvae (Austrosimulium furiosum), chironomid (Rheotanytarsus) and the mayflies and stoneflies. The only fish collected was the introduced mosquitofish (Gambusia).
The water was slightly saline in autumn (salinity of 3,008 mg/L) and fresh in spring (salinity of 706 mg/L), moderately well to well oxygenated (50–73% saturation), clear but strongly coloured, with moderate to high concentrations of nutrients such as nitrogen (0.89–2.48 mg/L) and phosphorus (0.06-0.47 mg/L).
The sediments were dominated by boulders, cobbles, pebbles, and algae in the fast-flowing habitats and detritus, sand and algae in the still and slow-flowing areas. Samples taken from below the surface were blackened, sulphidic and anaerobic in autumn, indicating that too much organic matter had entered the creek in the past. Subsequent sampling in spring showed that the sediments were aerobic, presumably in response to the strong flows down the creek in recent months. A deposit of 1–5 cm of silt covered the creekbed in both autumn and spring, and a small amount of bank erosion was noted in spring due to past flood damage.
More than 10% of the site was covered in filamentous algae (Spirogyra) and a similar area was covered by aquatic plants, including floating (Spirodela) and emergent species (Cyperus, Phragmites, Rumex, Isolepis, Juncus, Triglochin and Typha). The riparian zone consisted of scattered River Red Gums and acacias over an understorey of reeds, introduced grasses and weeds. The surrounding vegetation was largely made up of introduced grasses, bracken and weeds under a canopy of scattered gums and acacias.
Special enironmental features
Currency Creek provides an important habitat for at least one species of leptophlebiid mayfly and two families of stonefly. Recent fish surveys in the catchment have also recorded the presence of at least two threatened fish species (Mountain Galaxias and Congolli) from the mid to lower sections of the creek (M Hammer, Aquasave Consultants, 2009).
Pressures and management responses
|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 SA Murray–Darling Basin NRM Board acknowledges the significant impacts that livestock have on aquatic environments and seeks to provide free technical advice and incentives to land managers for fencing and other works as funding permits. Funding incentives are limited in value and extent and require land managers to volunteer to be involved.|
|Limited riparian vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The SA Murray–Darling Basin NRM Board recognises that the management of riparian vegetation requires a long-term, integrated approach to achieve ecosystem benefits. The board therefore provides free technical advice on a range of topics for land managers and various incentives for works as funding permits.|
|Insufficient natural water flows resulting from water extraction and climate variability (reducing ecological integrity.||The SA Murray–Darling Basin NRM Board is working with the Department for Water and the community to develop a water allocation plan and licensing system which aim to balance social, economic and environmental needs for water. The objective for providing water to the environment is to maintain and/or restore self-sustaining water-dependent ecosystems which are resilient in times of drought.|
|Widespread introduced trees and weeds in the riparian zone at the site and upstream in the catchment (reducing habitat quality).||The SA Murray–Darling Basin NRM Board recognises the limitations of available funds relative to the scale of the degradation caused by introduced trees and weeds. The NRM Board provides free technical advice and community education to assist land managers in dealing with the integrated management of aquatic weeds. The NRM Board also has a targeted process, as directed by State Government, to strictly prioritise its investment in weed control activities as funds are limited. The NRM Board actively seeks funding opportunities for weed control; most opportunities are for locations where biodiversity outcomes can be achieved.|