Minniribbie Creek, near Wangary
2010 Aquatic Ecosystem Condition Report
- Dry in autumn and non-flowing, saline creek in spring.
- Very sparse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of gross nutrient enrichment.
- Riparian vegetation consisted of both dead and living trees over introduced grasses and samphire.
- Moderately eroded banks and large amount of silt deposited in the channel.
About the location
Minniribbie Creek is a small stream in Eyre Peninsula that originates as the outflow from Lake Wangary and discharges into Kellidie Bay. The creek represents the downstream extent of Glengyle Creek that flows into Lake Wangary. The major land uses are sheep grazing and cropping.
The monitoring site was located off Katies Lane, about one kilometre south of Wangary.
Eyre Peninsula NRM Regional Summary 2010
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, poor riparian habitat, silt deposition and bank erosion.
A very sparse community of only four species of macroinvertebrates was collected from the non-flowing creek, six metres wide and 55 centimetres deep, in spring 2010; the site was dry in autumn. The community was dominated by large numbers of salt tolerant snails (Coxiella) but included smaller numbers of amphipods (Austrochiltonia australis), a chironomid (Dicrotendipes) and lestid damselfly (Austolestes) that also frequently occur in saline streams and lakes. Small-mouthed Hardyhead fish were also collected from the site.
The water was saline (salinity of 8,623 mg/L), well oxygenated (136% saturation) and clear, with moderate to high nutrient concentrations such as nitrogen (1.44 mg/L) and phosphorus (0.02 mg/L).
The sediments were dominated by detritus, algae and sand; samples taken from below the surface were sandy grey and not obviously sulfidic or anaerobic. A deposit of 1-5 cm of silt was present in the channel and more than 10 metres of bank showed evidence of erosion, presumably due to flood damage in the past.
Over 35% of the site was covered by filamentous algae (Cladophora) and more than 65% of the channel was covered in aquatic plants such as a stonewort (Chara) and Sea Tassel (Ruppia).
The riparian zone consisted of dead eucalypts with some smaller gum trees and acacias in the upper storey over introduced grasses, samphire and sedges (Cyperus). The surrounding vegetation at the site was mostly cropping land and grazed grassland.
Special environmental features
Minniribbie Creek provides habitat for the Small-mouthed Hardyhead, a native fish that commonly occurs in coastal streams, lakes and estuaries in South Australia.
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).|
|Saline groundwater inflow (reducing ecological integrity).||The Eyre Peninsula NRM Board promotes the revegetation of recharge areas known to contribute to dryland salinity and encourages the adoption of perennial pastures as an alternative to annual cropping in these areas.|
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