Riparian vegetation consists of mostly native vegetation with a weedy understorey with dense woodland beyond
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 upstream from the waterfall at Waterfall Gully. The major land use in the 515 hectare catchment upstream from the site is nature conservation (89%), due to the protection provided by Cleland Conservation Park, with small areas also used for residential living, roads and stock grazing.
The creek was given a Very Good rating because the site sampled showed evidence of only minor changes in ecosystem structure and function, with many rare and sensitive macroinvertebrate species present. There were emerging signs of human disturbance including nutrient enrichment and the presence of weeds in the riparian zones but the stream provided an important refuge for many macroinvertebrate species in the region.
Findings
A highly diverse community of at least 43 species of macroinvertebrates was collected from this flowing creek, approximately 2 m wide and 35 cm deep, in autumn and spring 2015. The creek consisted of slow-flowing pools with fast-flowing riffle sections between the pools in both autumn and spring 2015. The site was dominated by non-biting midge larvae with high numbers of blackfly larvae (Austrosimulium and Simulium), scirtid beetles and the caddis fly Lingora in the riffles and the mayfly Tasmanocoenis in the pools. Other species collected in smaller numbers included a range of generalist and pollution tolerant species, such as snails, worms, mites, fly larvae from the dixid family, mayflies, waterbugs, stoneflies, dragonflies and caddisflies. Some sensitive and rare species, as well as flow-dependent species, were also collected, including the riffle beetle Simsonia, non-biting midge larva (Aphroteniella, Apsectrotanypus), mayflies (Offadens, Nousia and Thraulophlebia), stoneflies (Dinotoperla and Illiesoperla), the dragonfly Austrogomphus and Hemigomphus and the caddisflies Taschorema, Lingora, Cheumatopsyche and Triplectides similis. Introduced fauna such as the snail Potamopyrgus and the native fish Galaxias olidus (Mountain Galaxias) and water skinks were also seen at the site.
The water was fresh (salinity ranged from 181-188 mg/L), well oxygenated (91-99% saturation) and clear, with low concentrations of nutrients such as nitrogen (0.21-0.32 mg/L) and phosphorus (0.011 mg/L).
The sediments were dominated by cobbles, pebbles and gravel with some detritus also present. Samples taken from below the surface were sandy and showed no evidence of being anaerobic, or lacking oxygen. Only small deposits of silt covered the streambed to a depth of about 1 cm in places and no significant areas of bank erosion were seen.
A small amount of phytoplankton (chlorophyll a ranged from <0.1-0.86 µg/L) and small amounts (<10%) of filamentous algae (Spirogyra) were recorded from the site in spring. More than 10% of site was covered by a range of emergent plants (Juncus articulatus, Polygonum, Phragmites and Typha). The riparian zone consisted of scattered acacias and tea trees with a weedy understorey. The surrounding vegetation was dense native woodland.
Special environmental features
First Creek provides important habitat for many species sensitive to pollution and dependent on the near permanent flows that occur in this creek such as blackfly larvae, riffle beetles, the mayflies Offadens, Nousia and Thraulophlebia, the stoneflies Dinotoperla and Illiesoperla, the dragonflies Austrogomphus and Hemigomphus and the caddisflies Taschorema, Lingora, Cheumatopsyche and Triplectides similis. This creek is one of the most important in the region and one of the few that can be considered to be in a “least disturbed” state due to high native vegetation cover in the catchment, limited development or agriculture and very fresh water.
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.
Insufficient natural water flows in the creek resulting from water extraction and climate variability (reducing ecological integrity).
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.
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.