First Creek, Cleland Conservation Park
2012 Aquatic Ecosystem Condition Report
Permanently wet freshwater creek which was flowing in spring 2011 and autumn 2012
Diverse macroinvertebrate community with many rare and sensitive species
Emerging signs of nutrient enrichment
Riparian vegetation mostly native species
About the location
The southern tributary of First Creek rises about 1.5 kilometres south from Mount Lofty and flows in a north-westerly direction to meet the northern tributary of the creek. First creek then flows in a westerly direction through the Cleland Conservation Park before entering metropolitan Adelaide, where it flows through the suburbs to meet the Torrens River near the Adelaide Zoo. The major land uses in the 310 hectare catchment are conservation park (84%) and urban residential areas (6%). The monitoring site was located on the southern tributary of the creek within the Cleland Conservation Park, just upstream of the confluence with the northern branch near Chinaman’s Hut.
The creek was given a Very Good rating because the site sampled showed evidence of very little changes in ecosystem structure and function, with many rare and sensitive macroinvertebrate species present. There was evidence of human disturbance including emerging signs of nutrient enrichment but the stream still provided an important refuge for many macroinvertebrate species in the region.
A diverse community of at least 71 species of macroinvertebrates was collected from this flowing creek, approximately 1.1 m wide and up to 19 cm deep in spring 2011 and autumn 2012. The community was dominated by leptocerid caddisflies and non-biting midges (Tanytarsus and Cricotopus) in spring 2011, and stoneflies and round worms in autumn 2012. Other species collected in smaller numbers included a range of generalist and pollution tolerant species including segmented worms, five mites, springtails, craneflies, five species of biting midge, at least 21 species of non-biting midge, a common species of mayfly (Tasmanocoenis), small water striders, dragonflies and caddisflies. Many rare and sensitive species were collected from this site including the riffle beetle Simsonia, flow-dependent blackfly larvae (Austrosimulium and Paracnephia), larvae from the dipteran fly family Thaumaleidae, non-biting midges (Aphroteniella, Parochlus, Stictocladius, Bryophanocladius, Riethia and Stenochironomus), the dragonfly Synthemis eustalacta, stoneflies (Dinotoperla, Illiesoperla, Newmanoperla, Austrocerca) and caddisflies (Taschorema, Ulmerochorema, Lingora, Atriplectides and Triplectides similis). Fish larvae were also seen at the site but were too small to be identified.
The water was fresh (salinity ranged from 149-169 mg/L), well oxygenated (81-90% saturation) and clear, with low concentrations of nutrients such as nitrogen (0.22-0.27 mg/L) and phosphorus (0.009-0.015 mg/L).
The sediments were dominated by mainly cobbles, pebbles and boulders. Samples taken from below the surface were sandy grey and showed no signs of being anaerobic or lacking oxygen. No bank erosion was evident at the site sampled.
A moderate amount of phytoplankton (chlorophyll a ranged from 0.78-9.45 µg/L) and small amounts of blue-green algae (chlorophyll b ranged from <0.1-0.69 µg/L) were recorded. Small amounts of filamentous algae (Spirogyra) were seen at the site in both spring 2011 and autumn 2012. Less than 10% of the site was covered by aquatic plants including Crassula, Berula, Carex and Ottelia. The riparian zone consisted of Phragmites, Gahnia, bracken, Carex, blackberries, native shrubs, wattles and tea trees. The surrounding vegetation comprised of dense native vegetation including eucalypts, bracken, native shrubs, acacias, tea trees and Callitris.
Special environmental values
First Creek provides important habitat for a range of rare, sensitive and flow-dependent aquatic macroinvertebrates from the region. It has consistently been one of the most biodiverse and important streams in the Mount Lofty Ranges for over the past two decades.
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