Neekena Creek, Winkies Waterhole
2012 Aquatic Ecosystem Condition Report
- Ephemeral, non-flowing, waterhole when sampled in autumn 2012
- Sparse macroinvertebrate community with no rare or sensitive species
- Water was fresh, clear and enriched with nutrients
- Riparian vegetation consisted of native trees and shrubs and two species of aquatic plant were recorded
About the location
Nekeena Creek is a medium sized stream in the Far North of the State that rises about 75 km east from Oodnadatta and flows in an easterly direction before eventually discharging into the lower reaches of the Macumba River. This river drains into the northern part of Lake Eyre North. The major land use in the catchment is cattle grazing. The monitoring site was located off a track about 60 km east from Macumba Homestead and 85 kilometres east from Oodnadatta.
The creek was given a Fair rating because the site sampled showed evidence of moderate changes in ecosystem structure, and some changes to the way the ecosystem functions. There was evidence of human disturbance including nutrient enrichment, fine sediment deposition and cattle faeces deposited on the banks but the stream still provided habitat for some common species of aquatic macroinvertebrates.
A sparse community of at least 9 species of macroinvertebrates was collected from the shallow, isolated, 11 hectare waterhole in autumn 2012. The community was dominated by large numbers of waterbugs (Micronecta) and chironomids (Dicrotendipes, Ablabesmyia and Tanytarsus), and included smaller numbers of caddisflies (Triplectides australis), dytiscid beetles (Megaporus howitti and Antiporus blakei), waterbugs (Agraptocorixa parvipunctata) and coenagrionid damselflies. All are very tolerant, generalist insect species, capable of aerially dispersing throughout the arid stream network in the north of the State. No rare or sensitive species were collected and the lack of snails, mites, crustaceans, mayflies, long-lived dragonfly nymphs or any flow-dependent species indicates that the site probably dries during at least some years. Yabby holes were recorded around the margins of the waterhole which indicates that the site is likely to remain wet in most years; this species is capable of surviving periods of surface drying by sheltering in wet burrows for several months during droughts. The zooplankton community was unremarkable and consisted of moderate numbers of ostracods and cladocerans. No fish were seen at the site during the site inspection.
The water was fresh (salinity of 278 mg/L), saturated with oxygen (139% saturation), slightly coloured and clear, with moderate to high concentrations of nutrients such as nitrogen (1.39 mg/L) and phosphorus (0.07 mg/L).
The sediments were dominated by clay, detritus and silt, with smaller amounts of sand and algae also present; samples taken from below the surface were sulfidic grey sands that had an anaerobic odour, indicating that the sediments were organically enriched and lacking in oxygen. Over 5 cm of silt was deposited in the waterhole but no evidence of any significant bank erosion was present despite cattle faeces being recorded from the banks and along the edges of the waterhole.
A large growth of phytoplankton was present (chlorophyll a 18 Âµg/L) which included a small amount of blue-green algae or cyanobacteria (chlorophyll a 1.2 Âµg/L). Less than 10% of the shallow margins of the waterhole were covered by a type of filamentous alga (Cladophora), and a similar area was covered by two aquatic plants (submerged Myriophyllum and emergent Cyperus). The riparian vegetation was dominated by acacias and gum trees on the poorly vegetated banks (25-49% vegetative cover). The surrounding vegetation at the site comprised low saltbush shrubland.
Special environmental features
None detected apart from the presence of the submerged aquatic plant that is not commonly seen from creeks in the region.
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.|