Permanent flowing stream in autumn and spring 2016
Diverse macroinvertebrate community with many rare, sensitive and flow-dependent species present
Water was fresh, clear, with moderate nutrient levels
Riparian vegetation consisted of mainly native vegetation with some weeds and deciduous trees
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 it 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 nutrient enrichment and the extent of weeds in the riparian zone but the stream provides habitat for a significant number of rare, sensitive and flow-dependent species.
Findings
A diverse community of at least 44 species of macroinvertebrates was collected from the creek (31 species in autumn and 29 in spring), approximately 2 m wide and up to 20 cm deep, in autumn and spring 2016. The creek consisted of a connected flowing channel in both seasons sampled. The community was dominated by large numbers of black fly larvae and chironomids. It also included low to moderate numbers of springtails, dixid flies, waterbugs, odonates, mayflies, stoneflies and a variety of caddisflies. A number of rare and sensitive species were collected, including an amphipod (Family Talitridae), mayflies (Offadens Genus 1 sp 5, Nousia fuscula and Thraulophlebia inconspicua), blackflies (Austrosimulium furiosum and Paracnephia), odonates (Austrogomphus and Hemigomphus gouldii), stoneflies (Illiesoperla mayi, Dinotoperla evansi and Newmanoperla thoreyi) and caddisflies (Taschorema evansi,Ulmerochorema membrum, Lingora aurata and Atriplectides dubius). A range of species normally associated with flowing water were also collected, including the above- listed mayflies, stoneflies, caddisflies and blackflies, and another widely distributed blackfly (Simulium ornatipes) recorded in spring. The introduced brown trout was the only fish seen at the site and yabby holes were also seen along the wet banks of the stream.
The water was fresh (salinity ranged from 90-188 mg/L), well oxygenated (89-97% saturation), clear, and with variable nutrient levels that included low to moderate phosphorus (0.01-0.03 mg/L) and moderate to high nitrogen (0.39-0.62 mg/L) concentrations.
The sediments were dominated by detritus, boulders and cobbles with silt also found deposited in the slow-flowing sections. Smaller amounts of pebbles, gravel and sand were also present. Samples taken from below the surface were grey sands, silts and clays that were not anaerobic (lacking in oxygen). Due to the artificial stone and concreted banks there was no sign of any bank erosion.
No filamentous algae was seen in either autumn or spring, although moderate amounts of phytoplankton were recorded in spring (chlorophyll a ranged from <0.1-2.6 μg/L). Over 35% of the creek was covered by a range of aquatic plants, including Cyperus, Persicaria, Ranunculus and Typha. The riparian zone consisted of blackberry bushes and mint, scattered gums and acacias. The surrounding vegetation comprised areas of dense native woodland with a few deciduous trees closer to the waterfall.
Special environmental features
First Creek provides a permanently flowing, freshwater stream that consistently supports a diverse range of aquatic biota, including many rare, sensitive and flow-dependent species. The creek provides an important refuge habitat for many of these species and is among the most significant biodiversity hotspots in the region and State.
Pressures and management responses
Pressures
Management responses
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, including local government, to control weeds on their property and to help stop the spread to other properties and waterways.
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.
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
