Permanently fresh, flowing stream in autumn and spring 2016
Diverse macroinvertebrate community with many rare, sensitive and flow-dependent species recorded
Water was fresh, clear and enriched with nutrients
Riparian vegetation consisted of a sparse overstorey of native trees and shrubs over blackberries, sedges and grasses
Area map
About the location
Tunkalilla Creek rises near Parawa on the bottom of the Fleurieu Peninsula and flows in a southerly direction into 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 1,616 hectare catchment upstream from the site are grazing pastures (64%), native vegetation (12%) and softwood production (7.5%). The monitoring site was located between Eric Bonython Conservation Park and Rymill Road, about 4 kilometres south from Parawa.
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 a weedy riparian zone and elevated nutrient concentrations but the stream provides habitat for a large number of rare, sensitive and flow-dependent species of macroinvertebrates and native fish species.
Findings
A diverse community of at least 45 species of macroinvertebrates was collected from the creek (24 species in autumn and 32 in spring), 1-4.2 m wide and up to 60 cm deep, in autumn and spring 2016. The creek consisted of equal areas of slow-flowing pools and fast-flowing riffles in autumn and slightly more pools and less riffles in spring. The community was dominated by amphipods, leptophlebiid mayflies and waterbugs in the pools and by blackflies in the riffles. Low numbers of a number of other macroinvertebrates were also collected, including snails, worms, mites, yabbies, springtails, beetles, craneflies, dixids, mosquitoes, chironomids, baetid mayflies, stoneflies, dragonflies and caddisflies. A number of rare, sensitive and/or flow-dependent species were also collected from the site, including a mite (Family Mideopsidae, Gretacarus species), blackfly (Austrosimulium furiosum), chironomid (Rheotanytarsus), mayflies (Offadens sp. 5, Atalophlebia australasica, Nousia fuscula and Thraulophlebia inconspicua), a stonefly (Austrocerca tasmanica) and caddisflies (Taschorema evansi, Taschorema complex, Oxyethira columba, Cheumatopsyche modica and Triplectides similis). Several larval fish were also collected from the riffle habitat in autumn, which were probably a native galaxiid species.
The water was fresh (salinity ranged from 137-142 mg/L), well oxygenated (74-79% saturation), clear but slightly coloured, and with moderate to high concentrations of nutrients such as phosphorus (0.05-0.06 mg/L) and nitrogen (1.11-1.30 mg/L).
The sediments were dominated by detritus, silt and sand; samples taken from below the surface were mostly grey clay and silt that released sulfide when tested in spring, indicating that the sediments were occasionally anaerobic and lacking in oxygen. There was no evidence of any significant bank erosion and the only animal droppings seen in the vicinity of the creek were from kangaroos.
Only a small to moderate amount of phytoplankton was recorded during the year (chlorophyll a ranged from 1.23-2.25 μg/L) but no filamentous algae was seen in the creek. Over 35% of the channel was covered by aquatic plants, including pondweed (Stuckenia), sedges (Eleocharis), pennywort (Hydrocotyle), rushes (Juncus), water ribbons (Triglochin), knotweed (Persicaria) and weedy watercress (Rorippa). The riparian zone included a few gums, wattles, tea-trees and weedy blackberries over introduced grasses, rushes and sedges. The surrounding vegetation comprised dense eucalypt woodland over yaccas and blackberries.
Special environmental features
The stream supports a wide number of rare, sensitive, flow-dependent, generalist and tolerant species of macroinvertebrates, and maintained flowing freshwater habitats during 2016.
Pressures and management responses
Pressures
Management responses
Nutrient inputs to the creek from numerous diffuse sources (potentially leading to excess growth of algae and aquatic weeds)
The Adelaide and Mount Lofty Ranges NRM Board land management program encourages and promotes managing land to improve water quality. This includes working with industry and landholders to ensure efficient use of fertilisers and discuss ways to reduce runoff of nutrients into waterways.
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
