Peake Creek, Peake Crossing
2012 Aquatic Ecosystem Condition Report
- Semi-permanent, non-flowing waterhole when sampled in autumn 2012
- Sparse macroinvertebrate community with no rare or sensitive species
- Water was highly saline, clear and enriched with nutrients
- Riparian vegetation consisted of native shrubs and scattered trees and a salt-tolerant aquatic plant was present
About the location
Peake Creek is a medium sized stream in the Far North of the State that rises near Mount Willoughby as a series of tributary streams that include Arckaringa and Lora creeks. These streams converge to form Peake Creek to the east of Mount Barry, which then continues in an easterly direction for over 80 kilometres where it eventually discharges into the Neales River during exceptionally wet years. The Neales River then flows into the western side of Lake Eyre North, also only during very wet years. The highly saline soils limits land use within the catchment to cattle grazing and mining exploration activities. The monitoring site was located near Peake Creek Siding off the Oodnadatta Track, about 65 km south from Oodnadatta.
The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure, and moderate changes to the way the ecosystem functions. There was considerable evidence of human disturbance including nutrient enrichment, fine sediment deposition and cattle accessing the banks. The naturally high salinity of the stream would, however, have contributed towards the poor rating for the site because few aquatic macroinvertebrates and freshwater plants can tolerate salinities over 10,000 mg/L. Consequently, unlike other sites sampled from the region, natural factors probably combined with human induced land use pressures, to create a harsh environment for most aquatic species to be able to inhabit Peake Creek.
A sparse community of only 4 species of macroinvertebrates was collected from the non-flowing creek, 25 m wide and less than 25 cm deep, in autumn 2012. The community was not dominated by any species but included low numbers of dytiscid beetles (Necterosoma penicillatus and Allodessus), hydrophilid beetles (Berosus discolour) and a few chironomids (Procladius). All were saline tolerant insect species with good aerial dispersal capabilities. No sensitive, rare or flow-dependent species were collected and many macroinvertebrate groups (e.g. mites, snails, large crustaceans, waterbugs, odonates, caddisflies, mayflies and more chironomids, flies and beetles) normally expected from stream habitats were not recorded from the site. The high salinity would limit the ability for most macroinvertebrates to be able to colonise and then survive in this stream under the conditions measured in 2012. A small to moderate number of zooplankton were recorded, comprising mostly ostracods and a single copepod. The Desert Goby was the only fish collected from the site using dip nets.
The water was highly saline (salinity of 29,060 mg/L), well oxygenated (125% saturation), clear, and with moderate to high concentrations of nutrients such as nitrogen (2.8 mg/L) and phosphorus (0.04 mg/L).
The sediments were dominated by clay and silt, with smaller amounts of algae and detritus also present; samples taken from below the surface were anaerobic, black clays and silts which indicate that the sediments were lacking in oxygen. Over 10 cm of fine silt was deposited in the channel but no evidence of any significant bank erosion was recorded at the site. Cattle obviously access the banks of the creek because faeces were distributed throughout the site.
A moderate growth of phytoplankton was present (chlorophyll a 5.3 Âµg/L) which included a tiny amount of blue-green algae or cyanobacteria (chlorophyll b 0.5 Âµg/L). Large filamentous algal growths (Cladophora) covered more than 35% of the site and smaller growths of a salt tolerant, submerged aquatic plant (Ruppia) extended over 10% of the channel. The riparian vegetation was dominated by samphire and acacias on the moderately well vegetated banks (50-79% vegetative cover). The surrounding vegetation comprised scattered native shrubland of gums and acacias over samphire.
Special environmental features
No special environmental features were detected during the current survey but a detailed fish assessment carried out as part of the Lake Eyre Basin Rivers Assessment in May 2012, recorded a rich fish assemblage from the creek (Cockayne et al. 2013). At least 6 native (Lake Eyre Hardyhead, Bony Bream, Desert Goby, Spangled Perch, Desert Rainbowfish and Barred Grunter) and an introduced pest species (Mosquitofish) are known to inhabit Peake Creek. Most fish species found in the basin are not particularly sensitive to high salinity or nutrient enrichment, so while their presence indicates that the creek is occasionally an important refuge for native fish, it does not mean that it is in a good ecological condition.
Pressures and management responses
|Livestock have direct access at the site and upstream in the catchment exerting excessive grazing pressure on vegetation, causing sediment erosion and adding excessive nutrients to the watercourse.
|The SA Arid Lands Natural Resources Management Board recognizes that both direct and diffuse impacts on aquatic ecosystem condition can occur through direct stock access and excessive grazing pressure from stock and feral herbivores. Technical advice and incentives are offered to land managers in the region, as funding permits, to address these impacts through appropriate activities suitable for the context. In addition, projects are underway across the region to identify, prioritise and address impacts at key aquatic sites.
|Highly saline soils in the catchment.
|The EPA in collaboration with the Department for Environment, Water and Natural Resources is anticipating a study program to investigate the source(s) of high salinity in this region and its role in shaping aquatic ecosystems. This will assist in future condition assessments of highly saline waterways and clarify whether remediation efforts are warranted.