Riparian vegetation consists of mostly introduced species with vineyards and orchards beyond
Area map
About the location
Cox Creek is a small stream in the Southern Mount Lofty Ranges that rises near Uraidla and flows in a southerly direction, where it eventually discharges into the Onkaparinga River, south of Bridgewater. The monitoring site was located off Swamp Road in the Piccadilly Valley. The major land uses in the 539 hectare catchment are irrigated vegetables and vines (50%) and residential (25%), with minor areas used for other minimal uses, roads, grazing pastures, intensive horticulture, nature conservation, plantation forestry and dams.
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 the presence of weeds in the riparian zones. The stream provided habitat for few sensitive macroinvertebrate species.
Findings
A moderately diverse community of at least 34 species of macroinvertebrates was collected from this slow-flowing creek, approximately 5.5 m wide and up to 70 cm deep, in autumn and spring 2015. The creek consisted of connected slow-flowing pools in 2015. The site was dominated by snails such as the introduced Potamopyrgus and Physiella, as well as Glyptophysa and the bivalves Corbicula and Sphaerium. Turbellaria, worms and damselfly nymphs were also present in abundance. Other species collected in smaller numbers included a range of generalist and pollution tolerant species, such as the leech Glossiphonidae, non-biting midge and biting midge larvae, waterboatman, backswimmers, dragonflies and caddisflies. The more sensitive species; the stonefly Austrocerca tasmanica and the fish Mountain Galaxias (Galaxias olidus) were also collected from the site and the Bango frog (Limnodynastes dumerili) was heard calling.
The water was fresh (salinity ranged from 310-353 mg/L), well oxygenated (84-108% saturation) and clear, with moderate to high concentrations of nutrients such as nitrogen (0.52-2.54 mg/L) and phosphorus (0.066-0.083 mg/L).
The sediments were dominated by sand, silt, bedrock, and detritus with some pebble and gravel also present. Samples taken from below the surface were grey clay with some silt present and showed evidence of being anaerobic, or lacking oxygen during some months of the year. Only small deposits of silt covered the streambed to a depth of about 1 cm in places and no significant areas of bank erosion were seen.
A small amount of phytoplankton (chlorophyll a ranged from 1.84-2.45 µg/L) was recorded and more than 10% of the channel was covered in filamentous algae (Spirogyra and Cladophora). More than 10% of site was covered by a range of aquatic plants, including the emergent plants (Callitriche,Potamogeton, Polygonum and Rorrippa). The riparian zone consisted of willows with an understorey of blackberries and exotic creepers The surrounding landscape is vineyards and orchards.
Special environmental features
Cox Creek is a permanent freshwater creek that provides important habitat for a species of stonefly and fish such as the Mountain Galaxias.
Pressures and management responses
Pressures
Management responses
Widespread introduced 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.
Observed Condition
Expected Condition
