First Creek, flows to Tunkalilla Beach on the Fleurieu Peninsula
2011 Aquatic Ecosystem Condition Report
- Permanently wet, flowing, freshwater creek in autumn and spring 2011
- Diverse macroinvertebrate community with many rare, sensitive and flow-dependent species
- Obvious signs of moderate nutrient enrichment
- Riparian vegetation consists of native trees over a range of native and introduced understorey plants
About the location
First Creek is a small stream in the Southern Mount Lofty Ranges that rises near ‘Tunkalilla’ and flows southwards where it discharges onto Tunkalilla Beach in the Southern Ocean. The monitoring site was located off Tunkalilla Road, about 2 km east from Deep Creek Conservation Park on the Fleurieu Peninsula. The major land uses in the 226 hectare catchment are stock grazing and remnant native vegetation.
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. This stream provided an important refuge for many types of macroinvertebrate species found in the region. Despite this, there was evidence of human disturbance including nutrient enrichment and minor areas of bank erosion.
A diverse community of at least 60 species of macroinvertebrates was collected from the flowing creek, 0.9-6 m wide and up to 55 cm deep, in autumn and spring 2011. The community was dominated by a range of sensitive, generalist and pollution tolerant species, including chironomids, amphipods and baetid mayflies along the edges of pools and blackflies, chironomids, and conoesucid and hydrobiosid caddisflies. It also included smaller numbers of native and introduced snails, limpets, mites, springtails, beetles, craneflies, dixids, mosquitoes, biting midges, thaumaliids, leptophlebiid mayflies, waterbugs, odonates, stoneflies and many types of caddisflies. A large number of rare and/or sensitive species were collected from the site, including elmid beetles (Simsonia leai), blackfly larvae (Paracnephia, Austrosimulium furiosum and Simulium melatum), thaumaliids (Austrothaumalea MV sp.2), mayflies (Centroptilum elongatum, Atalophlebia australasica and Thraulophlebia inconspicua), stoneflies (Dinotoperla evansi, Illiesoperla mayi, Riekoperla naso and Austrocerca tasmanica) and caddisflies (Taschorema evansi, Ulmerochorema membrum, Oxyethira columba, Lingora, Leptorussa, Triplectides similis and specimens from the Family Tasimiidae). A number of species normally associated with flowing water were also collected, including a chironomid (Rheotanytarsus) and many of the above-listed rare and sensitive species. A number of unidentified, larval fish were collected from the fast-flowing riffle habitats in autumn; no other fish were seen at the site in 2011.
The water was fresh (salinity ranged from 268-644 mg/L), well oxygenated (95-122 % saturated), slightly turbid and coloured in spring, and with moderate to high concentrations of nutrients such as nitrogen (0.47-0.69 mg/L) and phosphorus (0.02-0.07 mg/L).
The sediments were dominated by detritus, clay and sand in the pools and boulders and cobbles in the riffles, although all sediment types were recorded at the site. Samples taken from below the surface were grey in colour and showed no evidence that the sediments were anaerobic or lacked oxygen. Minor silt deposits were noted from the pool habitats and about 10 m of bank showed evidence of erosion in spring due to cattle accessing the edge of the creek.
Only small amounts of algae were recorded from the site but more than 65% of the creek was covered by a range of aquatic plants. Large growths of water ribbons (Triglochin), introduced watercress (Rorippa) and knotweed (Persicaria) were noted but many other submerged (Callitriche) and emergent species (Cyperus, Eleocharis, Isolepis, Juncus and Rumex) were also present. The riparian zone was comprised an overstorey of gums and wattles, and an understorey of yaccas, sedges (Baumea) and introduced grasses and weeds. The surrounding vegetation was native scrubland consisting of various gums, wattles, yaccas, bracken and introduced grasses and weeds.
Special environmental features
First Creek provides one of the most significant refuges in the Mount Lofty Ranges and State for many rare, sensitive, flow-dependent and common species of aquatic macroinvertebrates.
Pressures and management responses
|Livestock having direct access at the site and upstream (causing sediment erosion and adding excessive nutrients).||The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes incentives for waterway and wetland fencing to exclude or limit stock from entering riparian zones.|
|Some 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.|
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.