Permanent flowing stream in autumn and spring 2013
Diverse macroinvertebrate community with many rare, sensitive and flow-dependent species
Water was fresh, clear and low in nutrients
Riparian vegetation consisted of planted native trees and shrubs over a weedy understorey downstream from the waterfall
Area map
About the location
First Creek is a small stream in the Southern Mount Lofty Ranges that rises on the western side of Mount Lofty and Crafers, and flows in a north-westerly direction where is becomes channelised through the north-eastern suburbs until it discharges into Torrens Lake near the Adelaide Zoo. The monitoring site was located downstream from the waterfall, near the kiosk at Waterfall Gully. The major land use in the 569 hectare catchment is conservation (Cleland Conservation Park), with smaller areas used for urban and rural residential living, roads, commercial activities and stock grazing.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was evidence of human disturbance due to the channelisation of the creekline and the extent of weed invasion along the wetter parts of the creek but the stream provides habitat for a number of rare, sensitive and flow-dependent species of macroinvertebrates.
Findings
A diverse community of at least 38 species of macroinvertebrates was collected from the creek (25 species in autumn and 28 in spring), 0.7-1.6 m wide and up to 60 cm deep, in autumn and spring 2013. The creek consisted of still to slow-flowing pools and areas with fast-flowing riffle habitats in both seasons sampled. The community was dominated by moderate numbers of sensitive groups such as mayflies, caddisflies and stoneflies in autumn and by blackflies, chironomids and mayflies in spring. It also included smaller numbers of introduced snails (Potamopyrgus), worms, yabbies, springtails, beetles, craneflies, dixid flies, biting midges and dragonflies (including Austrogomphus and Hemigomphus gouldii). Numerous rare, sensitive and/or flow-dependent species were collected including an elmid beetle (Simsonia leai), blackflies (Austrosimulium furiosum, Simulium melatum and Simulium ornatipes), chironomids (Rheotanytarsus and Cardiocladius), a mayfly (Atalophlebia australasica), stoneflies (Dinotoperla evansi and Illiesoperla mayii), caddisflies (Taschorema evansi, Cheumatopsyche sp. 2 and Lingora aurata), and the above listed dragonflies. A few native fish called Mountain Galaxias (Galaxius olidus) were also seen and caught at the site in spring.
The water was fresh (salinity ranged from 160-193 mg/L), well oxygenated (91-107% saturation) and clear, and with low concentrations of nutrients such as phosphorus (0.01 mg/L) and nitrogen (0.21-0.44 mg/L).
The sediments were dominated by detritus, silt, boulder and cobble, with smaller amounts of gravel, pebble and sand present; small amounts of filamentous algae was also present within the channel in spring. Samples taken from below the surface were sandy grey in appearance and showed evidence that the sediments were anaerobic and lacked oxygen during at least part of the year; the underside of rocks were slightly blackened and sulfide was being released from the sediments in autumn. This was probably due to decomposition of the large amount of organic detritus and amount of organic silt that was present at the site in 2013. Note that this contrasts with conditions at the same site in 2011, when coarse sediments dominated and there were no signs of any poorly oxygenated sediment.
There were no significant growths of phytoplankton or filamentous algae detected in autumn but over 10% of the creek was covered by a filamentous alga (Spirogyra) in spring. Over 35% of the creek was covered by a range of aquatic plants (Cyperus, Juncus, Persicaria and Typha) and weeds (introduced mint, bamboo and blackberries). The narrow riparian zone consisted of lawn grasses, planted gums, bottlebrush, sedges and blackberries on banks that have been channelised and protected to prevent erosion. The surrounding vegetation near the creek comprised planted deciduous trees around the carpark but native eucalypt woodland dominated the upstream catchment in the conservation park.
Special environmental features
First Creek provides a permanently flowing, freshwater stream that consistently supports a wide range of rare, sensitive and flow-dependent species. It is a major refuge for many species of mayflies, stoneflies and caddisflies, fish such as Mountain Galaxias and Common Galaxias, and a water skink (Eulampris quoyii). This creek represents one of the few “least disturbed” streams in the Mount Lofty Ranges with nearly 90% of its catchment located within a conservation park, and the remainder developed for peri-urban settlement. This contrasts with similar, well vegetated streams in the region where the extent of native vegetation typically ranges from 30-60%; only parts of Sixth Creek approach the vegetative cover still present in the First Creek catchment.
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.
Large nutrient and sediment inputs to the creek from numerous diffuse sources (leading to extensive growth of algae and aquatic weeds)
The Adelaide and Mount Lofty Ranges NRM Board’s 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.
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
