Poonana Creek, near Cleve
2010 Aquatic Ecosystem Condition Report
- Dry in autumn and consisting of a moderately fresh, slow-flowing stream in spring.
- Sparse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of moderate nutrient enrichment.
- Riparian vegetation mostly consisted of introduced grasses.
- Some bank erosion and fine sediment deposits in the creek due to water erosion and stock damage.
About the location
Poonana Creek is a small stream in Eyre Peninsula that rises to the west of Yeldulknie Conservation Park and drains in a south-westerly direction before discharging into Yeldulknie Creek to the south of Cleve. The major land uses are sheep grazing, cropping and native vegetation adjacent to the site sampled but a large part of the upper catchment comprised native vegetation adjacent to the conservation park. The disused Poonana Mine (copper, silver, lead and uranium) was located upstream from the monitoring site.
The site was located off an unsealed track originating to the north of Cleve, about three kilometres north-east of Cleve.
The creek was given a Fair rating because the site sampled showed 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 poor riparian habitat, although the stream still provided an important refuge for some macroinvertebrate species.
A sparse community of about 19 species of macroinvertebrates was collected from the slow-flowing creek, two metres wide and 42 centimetres deep, in spring 2010; the site was dry in autumn. The community was dominated by species tolerant to poor water quality such as beetles, chironomids, waterbugs, and leptocerid caddisflies. Blackfly larvae were seen in the small areas of faster flowing riffle habitats that occurred at the site. Another flow-dependent species, a dytiscid beetle larva (Platynectes decempunctatus), was also recorded from the creek. No sensitive or rare species were found.
The water was moderately fresh (salinity of 2,926 mg/L), well oxygenated (79% saturation), slightly turbid and coloured, with moderate to high concentrations of nutrients such as nitrogen (1.16 mg/L) and phosphorus (0.02 mg/L).
The sediments were dominated by detritus, clay and sand, with some pebbles and cobbles also present. Samples taken from below the surface were sulfidic and the underside surfaces of rocks were black, indicating too much organic matter had entered the creek in the past. A deposit of 1–5 centimetres of silt covered the creekbed in spring and nearly 10% of the site showed evidence of bank erosion caused by flooding and stock damage.
Emergent aquatic plants (Cyperus, Juncus and Isolepis) were growing in the channel and on the banks where they covered over 10% of the site. Smaller growths of filamentous algae (Cladophora) were also present and covered less than 10% of the site.
The riparian zone was dominated by introduced grasses and bare soil with some scattered gum trees, casuarinas and bottle brushes also present. The surrounding vegetation was cropping land with small patches of native vegetation on one bank.
Special environmental features
Poonana Creek provides habitat for at least two flow-dependent species that were collected from the slightly-flowing, moderately freshwater stream in spring 2010. Few other streams in the region supported flow-dependent species and the only other freshwater streams sampled in 2010 were Yeldulknie and Coonta creeks.
Pressures and management responses
|Livestock have direct access at the site and upstream in the catchment, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||
The Eyre Peninsula NRM Board promotes managing land to improve water quality. This includes incentives for:
|Limited natural riparian vegetation at the site and upstream in the catchment, providing minimal buffer protection from catchment landuses (reducing habitat quality).|