Munyallina Creek, Munyallina Spring
2012 Aquatic Ecosystem Condition Report
- Permanent flowing stream in autumn but contracted to isolated in-stream pools when sampled in spring 2012
- Diverse macroinvertebrate community with both regionally rare and flow dependent species present
- Water was moderately fresh, clear and moderately high in nutrients
- Riparian vegetation consisted of native trees and shrubs and the channel was covered by filamentous algae
About the location
Munyallina Creek rises south-west from Wooltana Cave in the Vulkathunha-Gammon Ranges National Park, and flows in a south-east direction across the Munyallina Valley for about 65 km, where it eventually discharges onto the plains located on the north-west margin of Lake Frome; flow rarely extends downstream onto the plains. The major land uses in the 7,903 hectare catchment, upstream from the site sampled, are grazing natural vegetation (68%) and national park (32%); however, the pastoral property within the catchment has not been grazed since the 1970’s. The monitoring site was located off a track from Copley Road, about 11.5 km north-east from Balcanoona Homestead and 12 km south-east from Arkaroola.
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 minor weed invasion along the access track to the site but the stream provides habitat for several rare, sensitive and flow-dependent species of macroinvertebrates.
A diverse community of at least 34 species of macroinvertebrates was collected from the creek, 1.4-2.8 m wide and up to 45 cm deep, in autumn and spring 2012. The creek consisted of still to slow-flowing pools and areas with fast-flowing riffle habitats in autumn but contracted to smaller, isolated pools in spring. The community was dominated by moderate numbers of chironomids, baetid mayflies (Cloeon), snails (Glyptophysa) and dytiscid beetles (Platynectes decempunctatus) from pool habitats, and the flowing riffles were dominated by blackflies (Simulium ornatipes), caddisflies (Cheumatopsyche), chironomids and mosquitoes (Anopheles). Other species were collected in much smaller numbers and included snails (Isidorella newcombi), mites, soldierflies and several types of beetles, biting midges, waterbugs, chironomids, dragonflies and caddisflies. The site supported at least one regionally rare species of snail (Isidorella), a sensitive but widely distributed mayfly and a few flow-dependent species were also collected during 2012, including the blackfly, caddisfly Cheumatopsyche and beetle Platynectes. Most species were generalists and tolerant insect groups, capable of dispersing aerially to other wetted habitats but the presence of at least two types of snails indicates that the stream normally stays wet at the site sampled.
The water was moderately fresh (salinity ranged from 1,401-1,491 mg/L), well oxygenated (78-237% saturation) and clear, and with moderate to high concentrations of nutrients such as phosphorus (0.04 mg/L) and nitrogen (0.87-1.22 mg/L).
The sediments were dominated by filamentous algae, with smaller amounts of bedrock, cobble and gravel in the pool habitats and cobble, pebble and finer sands and silts present in the riffle habitats; samples taken from below the surface were well-aerated grey sands in autumn when the stream was flowing but in spring when the stream ceased flowing, the sediments were slightly blackened and sulphidic, indicating that they were anaerobic, or lacking in oxygen. Over 1 cm of algae and organic matter covered the streambed in spring, which would have contributed to the poor condition of the underlying sediments. No evidence of any significant bank erosion was noted and the only animal faeces recorded from the edges of the creek were from kangaroos and emus.
A moderate amount of phytoplankton was present in spring (chlorophyll a 7.7 Âµg/L) and between 35-90% of the shallow margins of the creek was covered by filamentous algae (Cladophora and Spirogyra). No aquatic plants were recorded from the stream or its margins. The riparian vegetation was dominated by River Red Gums, acacias and paperbarks on the moderately well vegetated banks (50-79% vegetative cover). The surrounding vegetation at the site comprised low native woodland dominated by eucalypts and wattles. Some minor weed invasion of the site was associated with the access track but otherwise weed infestation of the creek was very low.
Special environmental values
Munyallina Creek is a largely natural, permanent stream in the Vulkathunha-Gammon Ranges to Lake Frome area that provides habitat for a wide range of aquatic macroinvertebrate species, including several flow-dependent species and some permanent pool species. Few human disturbances are evident due to limited access to most of the catchment and it appears that the current land management practices are not causing any significant damage in the vicinity of the site sampled.
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.|