Cooper Creek, Innamincka
2012 Aquatic Ecosystem Condition Report

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 a range of macroinvertebrates including some rare and sensitive species. Note that the high nutrient concentrations recorded from the waterhole were similar to other sites sampled from Cooper Creek and were assumed to have originated from upstream grazing and cropping practices. Similarly, the high turbidity was sourced by floods naturally mobilising clays from the channel country in Queensland and was not obviously exacerbated by local land use practices.

A moderately diverse community of at least 18 species of macroinvertebrates was collected from the 20 m wide, non-flowing, arid-zone channel in spring 2012. The community was dominated by moderate numbers of baetid mayflies (Cloeon), freshwater prawns (Macrobrachium) and chironomids (Cladopelma and Procladius), and included low numbers of 3 species of beetles, 3 waterbugs, 2 snails (Centrapala and Glyptophysa), 2 mayflies (Tasmanocoenis and Wundacaenis dostini), and yabbies, a biting midge, culicid mosquito (Anopheles) and a caddisfly (Triplectides). The community included groups normally associated with stream environments (prawns and snails) and others that are typically found in pool habitats and temporary waters throughout the Far North region (e.g. yabbies and insects such as beetles, bugs, flies, mayflies, mosquitoes and caddisflies). The baetid mayfly is a ubiquitous but sensitive species, normally found in large numbers from the permanent freshwater habitats in the region. The viviparid snail Centrapala and caenid mayfly W. dostini are rarely collected in the region and are probably indicator species for the maintenance of suitable permanent waterholes and reaches on the Cooper Creek system. Similarly, freshwater mussel shells (Velesunio) were seen around the edge, which provides further evidence of the significance of this channel reach as a refuge habitat for long-lived biota. The only fish caught was a single carp gudgeon (Hypseleotris) but no introduced fish were recorded from the site in 2012.    

The water was fresh (salinity of about 158 mg/L), well oxygenated (96% saturated) and turbid (secchi depth 9 cm), with high concentrations of nutrients such as nitrogen (1.98 mg/L) and phosphorus (0.44 mg/L). Small patches of oil were noted on the surface in places, which could be sourced from the breakdown of plants and algae or indicate some runoff from vehicles traversing the causeway.

The sediments were dominated by cobbles and living and dead detritus, with smaller amounts of boulder, pebble, sand, clay and silt; the coarse sediments probably originated from the construction of the causeway. Samples taken from below the surface of the sediment were sulfidic grey clays and silts, indicating that the sediments were occasionally anaerobic, or lacking in oxygen. No evidence of any significant bank erosion was noted but cattle faeces were noted on the edges of the channel.

A moderate amount of phytoplankton was present (chlorophyll a 8.8 µg/L) and nearly 10% of the shallow margins of the channel were covered by filamentous algae (Spirogyra). Over 10% of the channel was covered by introduced water couch and a native plant called Water Primrose (Ludwigia peploides). The riparian vegetation was dominated by lignum, couch grass, gum trees and acacias on the well vegetated banks (>80% vegetative cover). The surrounding vegetation comprised low gum and acacia woodland that extended a few hundred metres away from the waterhole and the Innamincka township.

Cooper Creek in the vicinity of Innamincka provides habitat for at least one native fish but probably also supports many of the species recorded further upstream in Cullyamurra Waterhole in 2011/2012 (Cockayne et al. 2013).

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• Cockayne, B., Schmarr, D., Duguid, A. & R. Mathwin (2013). “Lake Eyre Basin Rivers Assessment (LEBRA) 2012 Monitoring Report.” Report to LEBRA Oversight Group.
• Silcock, J. (2009). “Identification of Permanent Refuge Waterbodies in the Cooper Creek and Georgina-Diamantina River Catchments for Queensland and South Australia.” Final report to South Australia Arid Lands Natural Resource Management Board.
• Walker, K.F., Puckridge, J.T. & S.J. Blanch (1997). Irrigation development on Cooper Creek, central Australia – prospects for a regulated economy in a boom-and-bust ecology. Aquatic Conservation: Marine and Freshwater Ecosystems Volume 7, pages 63-73.