Weetootla Creek, Weetootla Gorge
2012 Aquatic Ecosystem Condition Report
- Semi-permanent, slow-flowing, intermittent stream when sampled in spring 2012
- Sparse macroinvertebrate community with two sensitive mayflies and one threatened native fish present
- Water was fresh, clear and high in nutrients
- Riparian vegetation consisted of native trees and shrubs and the channel was covered by native and introduced aquatic plants
About the location
Weetootla Creek is a small stream that rises north from Illinawortina Pound in the Vulkathunha-Gammon Ranges National Park and flows for about 12 km in a south-easterly and southerly direction where it discharges into Balcanoona Creek in Weetootla Gorge. Balcanoona Creek eventually discharges onto the plains surrounding the north-western side of Lake Frome during very wet years. The only land use in the 4,326 hectare catchment, upstream from the site sampled, is national park. The monitoring site was located off the Weetootla Gorge walking track from Arkaroola Road, about 7 km north from Balcanoona homestead.
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 including nutrient enrichment and weedy riparian zones but the stream provides habitat for at least two sensitive macroinvertebrates and one threatened native fish.
A sparse community of at least 15 species of macroinvertebrates was collected from the creek, 2.8 m wide and up to 31 cm deep, in spring 2012; the site was not sampled in autumn. The community was dominated by large numbers of baetid mayflies (Cloeon and juveniles) and included smaller numbers of biting midges (Dasyhelea), caenid mayflies (Tasmanocoenis tillyardi), waterbugs (Microvelia peramoena, Agraptocorixa and Hydrometra), dragonflies and damselflies (Ischnura aurora and Diplacodes), beetles (Platynectes and Allodessus), caddisflies (Triplectides australis), mosquitoes (Anopheles), fly larvae (Stratiomyidae and Tabanidae) and freshwater limpets (Ferrissia). The high abundance of the two ubiquitous, sensitive species of mayflies was a notable feature of the aquatic biota, although the other macroinvertebrates collected were largely generalist and tolerant species with a widespread distribution in the region and State. The limpet was the only non-insect collected and its presence indicates the stream reach is probably permanently wet because it lacks strategies to cope with extended periods of drying. Only one flow dependent species (dytiscid beetle Platynectes) was collected but blackfly larvae (probably Simulium ornatipes) were also seen in the small areas of flowing riffle habitat that occurred in scattered parts of the creekline. The only rare or threatened species collected was the native fish, the Northern Purple Spotted Gudgeon.
The water was fresh (salinity of 758 mg/L), well oxygenated (64% saturation) and clear, with a low concentration of phosphorus (0.01 mg/L) but very high concentration of oxidised nitrogen (6.23 mg/L); the latter is typically high wherever nutrient enriched groundwater discharges as springs into Flinders Ranges streams.
The sediments were dominated by detritus, algae and bedrock, with smaller amounts of silt, pebble and gravel also present; samples taken from below the surface were gravels that showed no signs that the sediments were anaerobic, or lacking in oxygen. No evidence of any significant bank erosion was noted and the only animal faeces were recorded from the edges of the creek were from kangaroos.
Only a small amount of phytoplankton was present (chlorophyll a 1.5 Âµg/L) and over 35% of the shallow margins of the creek were covered by filamentous algae (Cladophora and Spirogyra). A similar area was covered by aquatic plants, including rushes and sedges (Juncus and Cyperus), large growths of introduced watercress (Rorippa) and small patches of cumbungi (Typha). The riparian vegetation was dominated by River Red Gums, acacias and Cypress Pine (Callitris) over sedges and various weeds (e.g. Salvation Jane) and grasses on the well vegetated banks (>80% vegetative cover). The surrounding vegetation at the site comprised native eucalypt woodland species.
Special environmental features
Weetootla Creek is a largely natural, permanent stream in the Gammon Ranges National Park that provides habitat for a critically endangered native fish species and a range of aquatic macroinvertebrates and plants. Few human disturbances are evident due in part to the remote location although riparian weeds and large herds of goats and other animal pests occur in the area on occasion.
Pressures and management responses
|Feral goats and donkeys are exerting excessive grazing pressure on vegetation, causing erosion and adding excessive nutrients to the watercourse.||The SA Arid Lands Natural Resources Management Board provides technical advice and incentives for the management of introduced weeds and feral pest animals, as funding permits. Pest management efforts are guided by a region-wide strategy, based on risk assessment, to determine priority locations and species. Funding is actively sought from a number of sources to support region-wide integrated management.|
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