Permanently fresh, flowing stream in autumn and spring 2016 but indications the site was only recently wet in autumn
Moderately diverse macroinvertebrate community with many rare, sensitive and flow-dependent species recorded
Water was fresh, clear, coloured and enriched with nitrogen
Riparian vegetation consisted of mostly native species and introduced grasses
Area map
About the location
Tunkalilla Creek rises near Parawa on the bottom of the Fleurieu Peninsula and flows in a southerly direction to the Southern Ocean. The swamps in the upper part of the Tunkalilla catchment have been included in a group of wetland habitats known as the Fleurieu Peninsula Swamps which have been listed as ‘critically endangered’ under the Environment Protection and Biodiversity Conservation Act 1999. The major land uses in the 618 hectare catchment upstream from the site sampled are grazing pastures (66%), native vegetation (23%) and softwood production (5%). The monitoring site was located upstream from Illawong Road near Waitpinga Conservation Park, about 3 km north-east from Deep Creek Conservation Park. The site was sampled slightly downstream from the original location in spring due to the greater diversity of habitat types present when the site was accessed.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was minor evidence of human disturbance due to the presence of elevated nitrogen concentrations and weedy grasses in the riparian zone but the stream provided significant habitat for a range of rare, sensitive and flow-dependent species of macroinvertebrates in spring.
Findings
A moderately diverse community of at least 32 species of macroinvertebrates was collected from the creek (6 species in autumn and 29 in spring), 1.1-2.6 m wide and up to 58 cm deep, in autumn and spring 2016. The creek consisted of mostly slow to non-flowing pools connected by fast-flowing riffles covering 30% of the site in autumn and 15% in spring. The community was dominated by moderate numbers of springtails in autumn and by blackflies, chironomids and stoneflies in spring. It also included smaller numbers of snails, worms, mites, amphipods, yabbies, biting midges, mayflies, waterbugs and caddisflies. A number of rare, sensitive and/or flow-sensitive species were collected at the site, including a mite (Australiobates), blackflies (Austrosimulium furiosum and Simulium ornatipes), a chironomid (Rheotanytarsus), mayfly (Thraulophlebia inconspicua), several stoneflies (Leptoperla tasmanica, Newmanoperla thoreyi, Riekoperla naso, Dinotoperla evansi and Austrocerca tasmanica) and three caddisflies (Taschorema evansi, Ulmerochorema membrum and Oxyethira columba). These significant species were only recorded in spring; the sparse community of generalist and tolerant species collected in autumn indicates the site may have only recently filled with water prior to that sampling period.
The water was fresh (salinity ranged from 109-121 mg/L), well oxygenated (69-81% saturation), clear and strongly coloured in autumn, and with generally low to high concentrations of nutrients such as phosphorus (0.011-0.014 mg/L) and nitrogen (0.63-0.71 mg/L).
The sediments were dominated by detritus, sand and silt in autumn and by bedrock in spring, but a range of other sediment types were also recorded, including cobble, silt and algae. Samples taken from below the surface were mostly detritus and grey silt that did not release any sulfide when tested, indicating that the sediments were well oxygenated. There was no evidence of any significant areas of bank erosion and the only animal droppings seen in the vicinity of the creek were from kangaroos.
Only a small amount of phytoplankton was recorded during the year (chlorophyll a ranged from <0.1-0.43 μg/L), and filamentous algae (Spirogyra) was only seen in spring, when it extended over nearly 10% of the creek. A similar area was also covered by aquatic plants, including sedges (Carex and Isolepis), pennywort (Hydrocotyle) and water ribbons (Triglochin). The riparian zone was mostly less than 5 m wide and comprised bracken, sedges and introduced grasses with a few scattered gums and wattles lining the stream. The surrounding terrestrial vegetation included areas of dense eucalypt woodland and partly cleared woodland with pines.
Special environmental features
The site supported a number of significant species of macroinvertebrates in spring, indicating that the upper reaches of Tunkalilla Creek are important refuge habitats for aquatic life in the wider catchment.
Pressures and management responses
Pressures
Management responses
Insufficient natural water flows in the creek resulting from water extraction and climate variability
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 weeds in the riparian zone at the site and upstream
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.
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Observed Condition
Expected Condition
