Isolated in-stream waterhole in autumn and spring 2012
Moderately diverse macroinvertebrate community with a few regionally rare and sensitive species present
Water was moderately fresh, clear and high in nutrients
Riparian vegetation consisted of native trees and shrubs but no aquatic plants or filamentous algae were evident
Area map
About the location
Arkaroola Creek is a large stream that rises off Mainwater Pound in the Vulkathunha-Gammon Ranges and flows south-east for about 55 km where it eventually discharges onto the plains surrounding the north-western edge of Lake Frome; flow only extends onto the plains during exceptionally wet years. The major land uses in the 18,661 hectare catchment, upstream from the site sampled, are grazing natural vegetation (58%) and national park (39%); however, the pastoral lease in the upstream catchment has not been grazed since the 1970’s. The monitoring site was located off the track to Stubbs Waterhole from Arkaroola Road in the Arkaroola Wildlife Sanctuary, about 6.5 km east-north-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 due to the level of nutrient enrichment but the waterhole provides a significant habitat for several rare and sensitive species of macroinvertebrates.
Findings
A moderately diverse community of at least 27 species of macroinvertebrates was collected from the isolated pool in the creek, 3.5-12 m wide and over 50 cm deep, in autumn and spring 2012. The community was dominated by large numbers of waterbugs (Micronecta and Anisops species) and caenid mayflies (Tasmanocoenis tillyardi) in autumn but only a sparse assemblage of species was present in spring. The community also included smaller numbers of mites (Limnesia), yabbies (Cherax), beetles (Antiporus, Sternopriscus, Necterosoma dispar, Macrogyrus, Paracymus andOchthebius), biting midges (Culicoides and Nilobezzia), chironomids (Procladius, Tanytarsus, Dicrotendipes and Polypedilum), baetid mayflies (Cloeon), waterbugs (Agraptocorixa), dragonflies (Diplacodes and Hemicordulia) and caddisflies (Ecnomus turgidus, Lectrides varians, Oecetis and Triplectides australis). The assemblage of species was notable due to the presence of two mayflies, which are sensitive freshwater groups in the Far North region, and a mite (Limnesia) and dytiscid beetle (Necterosoma dispar) which have rarely been collected from the Flinders Ranges in the past. Most groups, however, were tolerant and generalist insect groups that are widely found throughout the region. The only two non-insects collected included a mite and yabby, which may be able to survive brief periods of drying by sheltering below the surface among the wetter sediments. Presumably the site dries too regularly to enable snails and other molluscs from inhabiting this reach of the stream.
The water was moderately fresh (salinity ranged from 1,068-2,452 mg/L), well oxygenated (90-151% saturation) and clear, and with moderate to high concentrations of nutrients such as phosphorus (0.02-0.11 mg/L) and nitrogen (0.92-1.30 mg/L).
The sediments were dominated by sand, silt and bedrock, with smaller amounts of boulder, cobble, pebble, clay and detritus also present; samples taken from below the surface were grey sands in autumn but the sediments became blackened and sulphidic in spring, indicating that they were anaerobic, or lacking in oxygen. No evidence of any significant bank erosion was noted and the only animal faeces recorded from the edges of the creek were from kangaroos.
A moderate amount of phytoplankton was present in spring (chlorophyll a 9.8 µg/L) when measurable levels of cyanobacteria or blue-green algae (chlorophyll b 1.9 µg/L) were recorded. No filamentous algae or aquatic plants were observed during either site visit in 2012. The riparian vegetation was dominated by River Red Gums and acacias over sedges (Cyperus gymnocaulos) 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.
Special environmental features
Arkaroola Creek is a largely natural, permanent to semi-permanent stream in the Northern Flinders Ranges that provides habitat for a moderate diversity of aquatic macroinvertebrates, including a few sensitive and rare species for the region. Most of the upper catchment lies in the Arkaroola Wildlife Sanctuary, which is notable for its wildlife conservation values, threatened species, significant geological monuments and inclusion of various features in the Register of the National Estate.
Pressures and management responses
Pressures
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.
Observed Condition
Expected Condition
