Currency Creek, near Currency Creek
2010 Aquatic Ecosystem Condition Report
- Permanently wet, freshwater creek with isolated pools in autumn and a flowing channel in spring.
- Sparse macroinvertebrate community with some rare and sensitive species.
- Obvious signs of gross nutrient enrichment.
- Riparian vegetation consisted of introduced grasses under a canopy of gums and acacias.
About the location
Currency Creek is a moderately large stream in the southern Mount Lofty Range. It rises west of Mosquito Hill and flows in an easterly direction where it ultimately discharges into the Lower Murray, north of Goolwa. The major land uses are cattle and sheep grazing in the upper catchment and vineyards, recreational activities and areas of native vegetation in the lower reaches. The monitoring site was located off Currency Creek Road, nearly one kilometre south of Currency Creek.
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 considerable evidence of human disturbance, including nutrient enrichment, poor riparian habitat and fine sediment deposition, although the stream still provided an important refuge for some sensitive macroinvertebrate and native fish species.
A sparse community of about 25 species of macroinvertebrates was collected from this creek, 4-6 metres wide and up to 75 cm deep, in autumn and spring 2010. In autumn, the site consisted of a large still pool, however, the creek was flowing slowly in spring and included a small area of faster flowing riffle habitat that was too small to sample.
The community was comprised low numbers of only six species in autumn but was dominated by large numbers of introduced hydrobiid snails (Potamopyrgus antipodarum), chironomids, amphipods (Austrochiltonia australis) and blackfly larvae in spring. Smaller numbers of various other species were collected, including planorbid and introduced physid snails, worms, freshwater prawns, yabbies, beetles, mayflies, waterbugs, dragonflies, stoneflies and caddisflies. At least two rare and sensitive species were collected, including a leptophlebiid mayfly (Koorrnonga inconspicua) and gripopterygid stonefly (Illiesoperla mayi). A range of species normally associated with flowing habitats was recorded in spring, including a dytiscid beetle (Platynectes decempunctatus), blackfly larvae (Austrosimulium furiosum and Simulium ornatipes), chironomid (Rheotanytarsus) and the abovementioned sensitive mayfly and stonefly. Only two common species of native fish were recorded, including the Flathead Gudgeon and Australian Smelt.
The water was moderately fresh (salinity of 2,789 mg/L in autumn and 1,013 mg/L in spring), well oxygenated (63–90% saturation) and slightly coloured, with high concentrations of nutrients such as nitrogen (0.77–1.76 mg/L) and phosphorus (0.33–0.64 mg/L).
The sediments were dominated by detritus with silt and algae also present; samples taken from below the surface were black, sulphidic and anaerobic, 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 the slow-flowing areas in spring and less than 10 metres of bank showed evidence of erosion due to previous flood damage.
A large amount of phytoplankton was present in autumn and over 35% of the site was covered in filamentous algae (Spirogyra and Enteromorpha) in spring. Large growths of aquatic plants were also evident with over 65% and 35% the site covered in several emergent species (Phragmites, Typha, Rumex and Triglochin) in autumn and spring, respectively. The riparian zone consisted of introduced grasses and reeds (Phragmites) with a canopy of gum trees and acacias. The surrounding vegetation was patchy native vegetation and a recreational park and included gums, acacias, introduced grasses and a few sheoaks.
Special environmental features
Currency Creek provides habitat for a sensitive stonefly and mayfly species, and two commonly occurring native fish species. 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.|
|Feral predatory fish (trout and redfin) (reducing ecological integrity).||Local volunteer groups are undertaking works at some sites. The SA Murray–Darling Basin NRM Board opportunistically removes pest fish during monitoring activities. Other agencies are responsible for the control of pest fish and have undertaken some awareness-raising activities throughout the region.|