First Creek, u/s waterfall
2013 Aquatic Ecosystem Condition Report
- 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 native wattles and gums over introduced grasses and weeds
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. There was evidence of human disturbance due to the extent of weed invasion along the wetter parts of the creek and the presence of some signs of nutrient enrichment (eg presence and extent of filamentous algae in autumn). Despite this, the stream provides a significant habitat for a rich assemblage of rare, sensitive and flow-dependent species of macroinvertebrates for the region and State.
A diverse community of at least 44 species of macroinvertebrates was collected from the creek (29 species in autumn and 29 in spring), 1.2-2.5 m wide and up to 14 cm deep, in autumn and spring 2013. The creek consisted of mostly moderate to fast-flowing, shallow riffle habitats with smaller areas of slow-flowing or still, shallow pool habitats in both seasons sampled. The community was dominated by moderate numbers of caenid mayflies (Tasmanocoenis tillyardi) in the pools and included low numbers of turbellarians, nematodes, introduced snails (Potamopyrgus), worms, springtails, beetles (including the elmid Simsonia leai), dixid flies, biting midges (including Ceratopogon), blackflies (Austrosimulium furiosum, Simulium ornatipes and Paracnephia), chironomids (including Riethia), leptophlebiid mayflies (Offadens and Thraulophlebia inconspicua), waterbugs, dragonflies (including Hemigomphus gouldii and Archaeosynthemis macrostigma), stoneflies (Dinotoperla evansi) and caddisflies (including Taschorema, Lingora and Atriplectides). Most of the above-listed species were rare, sensitive and/or flow-dependent species from across a wide range of macroinvertebrate groups. The community also included some particularly rich macroinvertebrate groups, with five types of biting midges, eight caddisflies and nine chironomids collected during 2013.
The water was fresh (salinity ranged from 155-193 mg/L), well oxygenated (100-109% saturation) and clear, and with very low concentrations of nutrients such as phosphorus (0.01 mg/L) and nitrogen (0.14-0.48 mg/L).
The sediments were dominated by detritus, boulder, gravel and cobble with smaller amounts of pebble, sand, silt, and filamentous algae in autumn, also present. Samples taken from below the surface were grey silts, sands and clays and there was no evidence to indicate that the sediments had recently been anaerobic or lacking in oxygen. There were no signs of any significant areas of bank erosion and no animal droppings were seen on the banks of this stream during either site inspection.
There were no significant growths of phytoplankton recorded (chlorophyll a ranged from <0.1-0.7 μg/L) but a filamentous alga (Spirogyra) extended over more than 10% of the channel in autumn. A similar area was covered by a few types of aquatic plants, including a rush (Juncus), knotweed (Persicaria) and dock (Rumex). The narrow riparian zone consisted of a line of wattles and a few gum trees along each bank over introduced grasses and weeds. The surrounding vegetation near the creek comprised dense native woodland within Cleland 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 blackflies, elmid beetles, mayflies, stoneflies and caddisflies, fish such as Mountain Galaxias and Common Galaxias downstream from the waterfall, and a water skink (Eulampris quoyii). This creek probably represents the most natural stream in the Mount Lofty Ranges because only about 10% of the upstream catchment has been developed, and the remainder lies in a conservation park. This contrasts with other similar, least disturbed streams in the region where typically only 30-60% of the native vegetation remains following European settlement.
Pressures and management responses
|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.|
|Some nutrient inputs to the creek from diffuse sources (leading to 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.