Riparian vegetation mostly consisted of River Red Gums and wattles over sedges, introduced grasses and weeds.
Area map
About the location
Tanunda Creek is a small to moderately sized stream which rises in the Kaiserstuhl Conservation Park in the Barossa Valley and flows occasionally, draining west towards Bethany before disappearing underground in the North Para River catchment. The major land uses in the 2,355 hectare catchment upstream from the site sampled included grazing modified pastures (45%), other minimal uses (25%) and nature conservation (17%), with smaller areas of irrigated horticulture, roads, dams, plantation forestry, residential living, and cropping also present. The site selected for monitoring was located upstream from Bethany Reserve and the ford on Bethany Road.
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 due to the extent of riparian disturbance of the understorey vegetation and bank erosion caused by recreational use of the park.
Findings
A moderately diverse community of at least 28 species of macroinvertebrates was collected from the 1.4-6 m wide, 33 cm deep creek in spring; the creek was dry in autumn. The creek consisted of equal areas of moderately fast-flowing riffle habitats and still or slow-flowing deeper pools. The community was not dominated by any species but included low to moderate numbers of introduced and native snails (Potamopyrgus,Physa and Glyptophysa), limpets, amphipods, beetles, blackflies (Simulium ornatipes), chironomids, mayflies (including Atalophlebia australasica and Thraulophlebia inconspicua), waterbugs (including Paraplea), stoneflies (Dinotoperla evansi) and caddisflies. Most were tolerant and generalist species that have a wide distribution from organically enriched streams elsewhere in the State. No rare macroinvertebrates were collected but a few sensitive and/or flow-dependent species were recorded, including the above-listed blackfly, mayflies and stonefly.
The water was fresh (salinity 584 mg/L), well oxygenated (112% saturation), clear, and with moderate to high concentrations of nutrients such as phosphorus (0.03 mg/L) and nitrogen (0.82 mg/L).
The sediments were dominated by cobble, pebble, gravel and sand, with variable amounts of detritus, boulder and silt also present; samples taken from below the surface were grey silts, sands and rocks that released sulphide when tested in spring, indicating that the sediments were anaerobic and lacking in oxygen for at least part of the year. There was some bank erosion (<10%) noted at the site which appeared to be related to recreational use of the nearby park.
Only a small amount of phytoplankton was present when sampled (chlorophyll a of 0.3 μg/L) but patches of filamentous algae (Cladophora and Spirogyra) covered nearly 10% of the channel in spring. A slightly larger area was covered by a few types of aquatic plants (Cyperus, Juncus and Rumex). The narrow riparian zone was dominated by a line of River Red Gums, banksias, prickly wattles and a few introduced pine trees over introduced grasses and a few dock plants. The surrounding vegetation near the creek comprised cleared land with a few scattered gums, vineyards and lawns surrounding the carpark associated with the recreational park.
Special environmental features
The most significant feature of this creek was that it supported quite a diverse range of species, including a few sensitive and flow-dependent types of macroinvertebrates.
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.