Tributary of Cox Creek, south from Uraidla
2011 Aquatic Ecosystem Condition Report
- Permanently wet, slow-flowing, freshwater creek in autumn and spring 2011
- Sparse macroinvertebrate community with a few rare and sensitive species
- Obvious signs of moderate to gross nutrient enrichment
- Riparian vegetation dominated by woody weeds
About the location
This creek is a small, first-order stream in the Southern Mount Lofty Ranges that flows in a south-westerly direction into Cox Creek. The monitoring site was located off Richardson Road, about 1 km west from Mount Carey and 1.5 km south from Uraidla. The major land uses in the 46 hectare catchment are irrigated vegetables and vines, remnant native vegetation, rural residential living and stock grazing.
The creek was given a Fair rating because the site sampled showed evidence of moderate changes in ecosystem structure, and some changes to the way the ecosystem functions. There was evidence of human disturbance including nutrient enrichment and degraded riparian habitats. Despite this, the stream still provided habitat for some rare and sensitive macroinvertebrate species.
A sparse community of at least 23 species of macroinvertebrates was collected from the slow-flowing creek, 0.5-1 m wide and up to 10 cm deep, in autumn and spring 2011. The community was dominated by generalists and species tolerant to poor water quality such as hydrobiid and introduced physid snails, worms, chironomids and leptocerid caddisflies (Lectrides varians). It also included smaller numbers of flatworms, limpets, bivalves, mites, springtails, beetles, craneflies, blackflies, waterbugs, dragonflies, stoneflies and other types of caddisflies. Several rare, sensitive and/or flow-dependent species were recorded, including a blackfly (Austrosimulium furiosum), dytiscid beetle (Platynectes decempuncatus), stonefly (Austrocerca tasmanica) and hydrobiosid caddisfly (Taschorema evansi); most were detected in spring when flows were highest (0.2 metres/second). A threatened species of native fish called Mountain Galaxias (Galaxias olidus) was collected in autumn and a juvenile galaxiid fish was also found in spring.
The water was fresh (salinity ranged from 75-169 mg/L), well oxygenated (85-87% saturated), clear, and with high concentrations of nutrients such as nitrogen (1.5-2 mg/L) and phosphorus (0.06-0.16 mg/L).
The sediments were dominated by detritus and silt, with sand and gravel also present. Samples taken from below the surface were grey and anaerobic in autumn but the sediments appeared to be well-aerated in spring when the creek was flowing more extensively. A small amount of fine silt was deposited in the channel and no bank erosion was noted during either survey in 2011.
Over 90% of the creek was covered by aquatic plants, mostly comprising introduced watercress (Rorippa) and patches of dock (Rumex). The limited riparian zone was dominated by woody weeds (blackberries and broom) and the surrounding terrestrial vegetation was cleared grassland and rural gardens.
Special environmental features
This creek was the only first order stream sampled in 2011 that sustained flowing pool habitats and aquatic biota; the other 9 similar stream types were all dry. The creek was also notable because several rare, sensitive and flow dependent species of macroinvertebrates were present and it provided habitat for a state-listed, threatened native fish.
Pressures and management responses
|Insufficient natural water flows in the creek resulting from water extraction and climate variability i.e. drought (reducing ecological integrity.||Through water allocation planning the Adelaide and Mount Lofty Ranges NRM Board seeks to manage a sustainable water supply for the region so that there is enough water available for everyone (including the environment) even in drought conditions.|
|Widespread introduced trees and weeds in the riparian zone at the site and upstream (reducing habitat quality).||The Adelaide and Mount Lofty Ranges NRM Board has several pest plant (weed) mitigation and control programs. They work closely with landholders to control weeds on their property and to help stop the spread to other properties and waterways.|
This aquatic ecosystem condition report is based on monitoring data collected by the EPA. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.